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1
Black, Ann Charlotte. "Flavocytochrome c from Shewanella putrefaciens." Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/10823.
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Flavocytochrome c, a multihaem cytochrome from Shewanella putrefaciens induced under anaerobic conditions, was studied to investigate the physiological function of this protein. These studies comprised two facets: the cloning and sequence analysis of the structural gene for flavocytochrome c and a biochemical study of the fumarate reductase activity associated with flavocytochrome c. A S. putrefaciens genomic library was constructed in the expression vector pEX3. This library was screened in E. coli MM294 by colony hybridization of induced recombinants with antibody raised to purified flavocytochrome c protein. One clone giving a strong signal to antibody was identified from this library. Restriction digests of this recombinant showed the insert DNA to be approximately 1.5 kb. Southern blot analysis of the clone gave hybridization of flavocytochrome c antibody to a protein of approximately 45 kDa which was encoded by the recombinant pEX3 vector. This cloned fragment was proposed to encode part of the flavocytochrome c gene and investigated in more detail. The 1.5 kb cloned fragment was partially sequenced and mapped. Sequencing yielded two non-overlapping contigs of 438 bp and 966 bp respectively. The DNA fragment joining the two contigs remained unsequenced. Database analysis showed that the second contig contained 4 conserved c-type haem binding site motifs CXYCH within the first 90 residues. A second region in this contig from bases 123-151 was found to be completely homologous with a highly conserved FAD-binding fingerprint common to many flavoproteins. This molecular analysis strongly suggested that the cloned DNA fragment encoded at least 322 residues of the N-terminal region of the flavocytochrome c protein. This was further confirmed by the finding that the first 8 residues of the second contig were completely homologous with residues 6-13 of the N-terminal sequence of flavocytochrome c. Cloning the entire flavocytochrome c gene was attempted also by functional complementation of an E. coli fumarate reductase mutation.
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Morris, Christopher John. "C-type cytochromes of Shewanella putrefaciens." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/11195.
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Atanasiu, Doina. "Respiratory enzymes from Shewanella MR-1." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/11653.
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Shewanella MR-1 is a Gram-negative, facultatively anaerobic bacterium isolated from Lake Oneida, New York. It can couple its anaerobic growth to the reduction of a wide variety of compounds such as nitrate, nitrite, TMAO, DMSO, fumarate, manganese(IV) and iron(III) oxides, sulfite and thiosulfate. Analysis of the genome sequence reveals the presence of a large number of respiratory enzymes. Three of these proteins were selected for further study: a decaheme cytochrome c, a heptaheme cytpchrome c and a flavoprotein. Decaheme 129 (Cyc129) is 37% similar to MtrC, a decaheme protein from the same organisms that have been shown to be involved in iron(III) and manganese(IV) respiration. The DNA sequence indicated the presence of a lipoprotein signal sequence but the protein is loosely associated to the membrane. Compared to the wild-type strain, no phenotypic differences were noted when the cyc129 gene was disrupted by the insertion of an antibiotic cassette. The second protein, heptaheme 202 (Cyc202) is a soluble, periplasmic protein and is the only heptaheme cytochrome c in Shewanella MR-1. Phenotypic studies indicate that it might be involved in the electron transport to the outer-membrane located iron-manganese reductases. FccA56 is similar to the flavin domain of flavocytochrome c3 , the fumarate reductase from Shewanella MR-1. The gene encoding this protein is part of a cluster that also encodes a tetraheme c-type cytochrome and a histidine ammonia lyase-like protein. Substitution of the highly conserved amino acids involved in substrate binding suggests that fumarate is not the physiological substrate of FcA56, but has a similar substrate that contains only one carboxylic group. The protein was purified after overexpression in E. coli. A UV-visible absorption spectrum confirmed that the ~52 kDa protein has absorption maxima at 450 and 380 nm, characteristic for flavoproteins.
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Zhang, Mengni. "Dissimilatory iron reduction: insights from the interaction between Shewanella oneidensis MR-1 and ferric iron (oxy)(hydr)oxide mineral surfaces." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37129.
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Dissimilatory iron reduction (DIR) is significant to the biogeochemical cycling of iron, carbon and other elements, and may be applied to bioremediation of organic pollutants, toxic metals, and radionuclides; however, the mechanism(s) of DIR and factors controlling its kinetics are still unclear. To provide insights into these questions, the interaction between a common dissimilatory iron reducing bacterium (DIRB)was studied, Shewanella oneidensis MR-1, and ferric iron (Fe(III)) (oxy)(hydr)oxide mineral surfaces. Firstly, atomic force microscopy was used to study how S. oneidensis MR-1 dissolved Fe(III) (oxy)(hydr)oxides and compared it to two other cases where Fe(III) (oxy)(hydr)oxides were either dissolved by a chemical reductant or by a mutant with an electron shuttling compound. Without the electron shuttling compound, the mutant is unable to respire on Fe(III) (oxy)(hydr)oxides, but with the electron shuttling compound, it can. It was found that the cells of S. oneidensis MR-1 formed microcolonies on mineral surfaces and dissolved the minerals in a non-uniform way which was consistent with the shape of microcolonies, whereas Fe(III) (oxy)(hydr)oxides were uniformly dissolved in both of the other cases. Secondly, confocal microscopy was used to study the adhesion behavior of S. oneidensis MR-1 cells on Fe(III) (oxy)(hydr)oxide surfaces across a broad range of bulk cell densities. While the cells were evenly distributed under low bulk cell densities, microcolonies were observed at high bulk cell densities. This adhesion behavior was modeled by a new, two-step adhesion isotherm which fit better than a simple Langmuir or Freundlich isotherm. The results of these studies suggest that DIR is in-part transport limited and the surface cell density may control DIR.
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Rothery, Emma L. "Mechanistic studies on multiheme cytochromes from Shewanella." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/14338.
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Fumarate reduction in Shewanella is catalysed by a fumarate reductase known as flavocytochrome c3 (Fcc3). This enzyme consists of three domains: a cytochrome domain containing four c-type heme groups; a flavin domain containing a non-covalently bound FAD; and a mobile clamp domain. Fumarate is saccinate by hydride transfer from the flavin N5 and protonation by the active site acid, Arg402. Access of substrate to the active site in Fcc3 was believed to be controlled by movement of the clamp domain. To test this assumption, site-directed mutagenesis has been used to create a disulfide bond between the clamp and flavin domains via the double mutation A251C:S430C. The disulfide bond in the mutant enzyme has been confirmed by both crystal structure and Ellman analysis. When the disulfide bond is formed both the steady-state and pre-steady-state rate constants for fumarate reduction fall to 25 and 30% of the wild-type values respectively whilst KM values for fumarate are unaffected. Deuterium solvent kinetic isotope effects in the mutant enzyme are unchanged from wild-type (8.2 ±0.4 at pL 7.2), indicating that proton and/or hydride transfer is still rate-limiting. These results suggest that clamp domain mobility has little role in controlling fumarate reduction. The reduction of fumarate also requires the delivery of reducing equivalents to the active site. This is facilitated by the four bis-histidine-ligated heme groups within the cytochrome domain. Hemes I, II and III are solvent exposed and therefore able to collect electrons from the electron donor CymA, and deliver them to the FAD via heme IV. Mutations to His61, a ligand to the iron of heme IV, results in a lowering of both the steady-state and pre-steady-state rate constants for fumarate reduction (WT>H61Y>H61M>H61A). Crystal structures of H61A and H61M show that there is an exogenous ligand bound to the heme iron in both cases; acetate and water respectively.
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Gambari, Cyril. "Biogenèse de la pellicule chez Shewanella oneidensis." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0218/document.
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La bactérie aquatique Shewanella oneidensis est capable, en condition statique et en présence d'oxygène, de former un biofilm à l'interface air-liquide, appelé pellicule. Mon travail a porté sur la biogenèse de la pellicule.Il a été montré dans le groupe que le régulateur de réponse du système chimiotactique, la protéine CheY3, était impliqué dans la biogenèse de la pellicule. Cette protéine est essentielle dans les étapes précoces et tardives de sa formation alors que son partenaire habituel, CheA3, semble ne jouer un rôle que dans les étapes tardives. Mon travail s'est focalisé sur la recherche de partenaires de CheY3.J'ai introduit une banque d'ADN génomique de S. oneidensis dans la souche ΔcheY3 et j'ai cherché des gènes dont la surexpression permettait de restaurer la formation de la pellicule. Cette approche a révélé deux gènes pdgA et pdgB. J'ai montré que les protéines PdgA et PdgB étaient capables de synthétiser du di-GMPc, suggérant que ce messager secondaire est impliqué dans la biogenèse de la pellicule. L'hydrolyse du di-GMPc par des enzymes dédiées empêche en effet sa formation.J'ai montré que l'opéron mxd, contrôlant la synthèse d'exopolysaccharides dans les biofilms de surface, était impliqué dans la formation de la pellicule. La première protéine codée par cet opéron, MxdA, est capable de lier le di-GMPc. Des expériences de pontage chimique et de double hybride ont révélé que MxdA, CheY3, PdgA et PdgB, formaient un réseau de régulation gouvernant la biogenèse de la pellicule.J'ai montré que les systèmes à deux composants BarA/UvrY et ArcS/ArcA contrôlant la transcription de l'opéron mxd sont aussi impliqués dans la formation du biofilm flottantThe aquatic bacterium Shewanella oneidensis is able to form, under static conditions and in the presence of oxygen, a biofilm at the air-liquid interface, called pellicle. My work was focused on the biogenesis of this pellicle.It was previously shown in the team that, surprisingly, the CheY3 protein, the response regulator of the chemotactic regulatory system, is involved in the biogenesis of the pellicle. This protein was shown to be essential both in early and late steps of pellicle formation whereas its usual partner, the kinase CheA3, seems to play a role in the late steps only. I was therefore looked for the partners of the CheY3 protein for pellicle formation.For this purpose, I have introduced a multi-copy genomic library in the ΔcheY3 strain and searched for genes whose overexpression allowed pellicle restoration. Strikingly, this approach revealed two genes pdgA and pdgB. Interestingly, we showed that PdgA and PdgB proteins are able to synthesize c-di-GMP, suggesting a role for this second messenger in pellicle biogenesis. Indeed, c-di-GMP hydrolysis by dedicated enzymes blocks pellicle formation.We also showed that the mxd operon, controlling the exopolysaccharides synthesis in biofilm associated with a solid surface, is also involved in pellicle formation. Moreover, the first protein encoded by this operon, MxdA, is able to bind c-di-GMP. Cross-linking and bacterial two-hybrid experiments revealed that MxdA, CheY3, PdgA and PdgB, form a complex regulatory pathway governing the biogenesis of the pellicle.Finally, we have shown that the two-component systems BarA/UvrY and ArcS/ArcA, controlling the mxd transcription, are also involved in pellicle formation
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Moule, Anne Louise. "The cell envelope of Alteromonas putrefaciens (Shewanella putrefaciens)." Thesis, University of Hull, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314672.
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Davies, Jonathan A. "Characterisation of the reversible formate dehydrogenases of Shewanella." Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/66856/.
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The reversible action of tungsten or molybdenum-containing formate dehydrogenase (FDH) enzymes in reducing CO2 to formate has been proposed for storing renewably produced electricity with concomitant CO2 sequestration. Previous attempts have highlighted the unfeasibility of using purified enzyme systems for biotechnological purposes. In response the possibility of using the exoelectrogenic bacteria Shewanella oneidensis in association with a cathode to drive intracellular CO2 reduction is proposed. Since the native FDH enzymes of S.oneidensis have not been previously studied, this work concerns their characterisation and directionality to inform both on native physiology and possible future biotechnological applications. This thesis demonstrates that the native FDH enzymes of S.oneidensis are capable of CO2 reductase activity. Both forward (Km 39 μM) and reverse (Km 1.43 mM) directions of FDH catalysis in whole cell cultures are maximal when cultured in the presence of W. When grown under such conditions, two FDH isoforms (Fdh1αβγ and Fdh2αβγ) contribute to these activities, with protein purification confirming Fdh2αβγ as a tungstoenzyme. CO2 reductase activity in S.oneidensis cultures could be driven by a cathode in simple three electrode electrochemical experiments without exogenous mediators with high coloumbic efficiency, representing an interesting paradigm for future inexpensive microbial electrosynthetic study.
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Bilsland, Morag. "Novel respiratory flavocytochromes of Shewanella oneidensis MR-1." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/10812.
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Shewanella oneidensis MR-1 is a Gram-negative bacterium isolated from anaerobic freshwater lake sediments of Lake Oneida that exhibits remarkable respiratory versatility. In the absence of molecular oxygen, S. oneidensis MR-1 couples anaerobic growth to the reduction of various substrates, including ferric iron (FeIII), thiosulfate (S2O32-), sulfite (SO32-), trimethylamine N-oxide (TMAO), nitrate (NO3-), nitrite (NO2-) and organic substrates such was fumarate. The metabolic flexibility of S. oneidensis MR-1 is coupled to a complex and branched anaerobic respiratory chain. The respiratory enzymes of the fumarate reduction pathway have been extensively studied in S. oneidensis MR-1 and the related marine bacterium, S. frigidimarina NCIMB400. The terminal fumarate reductase of Shewanella is a soluble periplasmic flavocytochrome c3 (Fcc3) that catalyses the unidirectional production of succinate. The X-ray crystal structure of Fcc3 solved to high resolution provided the first detailed insight into the catalytic mechanism of fumarate reduction. In this work, the Fcc3 X-ray crystal structure provided a structural template to construct homology models of related flavoenzymes of unknown structure and function. The novel flavoenzymes were identified by sequence analysis of the S. oneidensis MR-1 genome and were shown to comprise separately encoded flavin (FccA54, FccA56 and FccA342) and cytochrome subunits (FccB54, FccB56 and FccB342), respectively, that were related by sequence to the corresponding domains in Fcc3. Molecular modelling of the catalytic flavin-binding subunits led to the suggestion that these related enzymes catalyse the reduction of acrylate-like substrates. Several biologically relevant plant metabolites, including phenylacrylates incorporated into lignin, were identified as potential substrates of the Fcc3-like enzymes. An fccA54 and fccB54 knockout strain of S. oneidensis MR-1 (MB5415) was constructed and grown anaerobically with each of the candidate acrylates to ascertain the biological function of FccA54.
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Silva, Amanda Lys dos Santos. "Estudos ecogen?micos e bioprospectivos de Shewanella spp." Universidade Federal do Rio Grande do Norte, 2009. http://repositorio.ufrn.br:8080/jspui/handle/123456789/16770.
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Bacteria trom Shewanella and Geobacter ganera are the most studied iron-reducing microorganisms particularly due to their electron transport systems and contribution to some industrial and environmental problems, including steel corrosion, bioenergy and bioremediation of petroleum-impacted sites. The present study was focused in two ways: the first is an in silico comparative ecogenomic study of Shewanella spp. with sequenced genomes, and the second is an experimental metagenomic work to detect iron-reducing Shewanella through PCR-DGGE of a metabolic gene. The in silico study resulted in positive correIation between copy number of 16S rDNA and genome size in Shewanella spp., with clusters of rrn near lhe origin of replication. This way, the genus is inferred as opportunist. There are no compact genomes and their sequences length varied, ranging from 4306142 nt in S. amazonensis SB2B to 5935403 nt in S. woodyi ATCC 51908, without correIation to temperature range characteristic of each specie. Intragenomic 16S rDNA sequences possess little divergence, but reasonable to resuIt in different phyIogenetic trees, depending on the sequence that is chosen to compare. For moIecuIar detection of iron-reducing Shewanella, it is proposed the mtrB gene as new biomarker. because it codes to a fundamental protein at Fe (III)-reduction. The specific primers were designed and evaluated in silico and resulted in a fragment of 360 pb. In the second study, these primers were tested in a genomic sample from S. oneidensis MR-1, amplifying the expected region. After this successfuI resuIt, the primer set was used as a tool to assess the iron-reducing communities of ShewaneIla genus under an environmental stress, i.e. crude oil contamination in mangrove sediment in Rio Grande do Norte State (Brazil). The primers presented high specificity and the reactions performed resulted in one single band of ampIification in the metagenomic samples. The fingerprinting obtained at DGGE reveaIed temporal variation of Shewanella spp. in analyzed samples. The resuIts presented show the detection of a biotechnological important group of microorganisms, the iron-reducing Shewanella spp. using a metabolic gane as target. It is concluded there are eight or more 16S rDNA sequences in Shewanella genus, with little divergence among them that affects the phylogeny; the pair of primers designed to ampIify mtrB sequences is a viable alternative to detect iron-reducing ShewanelIa in metagenomic approaches; such bacteria are present in the mangrove sediment anaIyzed, with temporal variations in the samples. This is the first experimental study that screened the iron-reducing Shewanella genus in a metagenomic experiment of mangrove sediments subjected to oil contamination through a key metabolic gene
Bact?rias dos g?neros Shewanella e Geobacter s?o os microrganismos redutores de ferro mais estudados. Esse interesse ocorre particularmente devido aos seus sistemas de transporte de el?trons e contribui??o em alguns problemas industriais e ambientais, tais como corros?o de oIeodutos, bioenergia e biorremedia??o de locais contaminados com petr?leo. O presente estudo foi tocado em duas partes: a primeira ? um estudo ecogen?mico comparativo de ShewanelIa spp. com genomas seq?enciados, e a segunda ? um trabalho metagen?mico experimental para detectar Shewanella redutoras de ferro atrav?s de PCR-DGGE de um gene metab?lico. O estudo in silico resultou em correla??o positiva entre o n?mero de c?pias 16S rDNA e tamanho do genoma em ShewaneIla spp., com agrupamentos de rrn. pr?ximo ? origem de replica??o. Desta maneira, o g?nero ? inferido como oportunista. N?o existem genomas compactos e o tamanho de suas sequ?ncias variam de 4306142 nt em S. amazonensis SB2B at? 5935403 nt em S. woodyi ATCC 51908, sem correla??o com a faixa de temperatura caracter?stica de cada esp?cie. Sequ?ncias intragen?micas de 16S rDNA possuem pouca diverg?ncia. mas razo?vel para resultar em diferentes ?rvores filogen?ticas. dependendo da sequ?ncia que ? escolhida para compara??o. Para a detec??o moIecuIar de ShewanelIa redutoras de ferro, ? proposto o gene mtrB como um novo biomarcador, por ser codante de uma prote?na fundamental na redu?ao de Fe (III). Os primers espec?ficos foram desenhados e avaliados in silico e resultou em um fragmento de 360 pb. No segundo estudo, esses primers foram testados em . amostra gen?mica de S. oneidensis MR-1, amplificando a regi?o esperada. Depois desse resultado favor?vel, o par de primers foi utilizado como ferramenta para acessar as comunidades redutoras de ferro do g?nero ShewanelIa sob um stress ambiental - contamina??o com ?leo cru em sedimento de mangue, no Estado do Grande do Norte (Brasil). Os primers apresentaram alta especificidade e as rea??es resultaram em banda ?nica de amplifica??o das amostras metagen?micas. O perfil obtido no DGGE revelou varia??o temporal de ShewanelIa spp. nas amostras analisadas. Os resultados apresentados mostram a defec??o de um grupo de microrganismos biotecnologicamente importante. ShewaneIla spp. redutoras de ferro, usando um gene metab?lico como alvo. Concluiu-se que existem oito ou mais sequ?ncias 16S rDNA no g?nero ShewaneIla, com pouca diverg?ncia entre elas que afetam a filogenia; o par de primers desenhados para amplificar sequ?ncias mtrB ? uma alternativa vi?vel para detectar Shewanella redutoras de ferro em abordagens metagen?micas; tais bact?rias est?o presentes no sedimento de mangue analisado, com varia??es temporais nas amostras. Este ? o primeiro estudo experimental que examina Shewanella redutoras de ferro em um experimento metagen?mico de sedimento de mangue submetido a contamina??o por ?leo atrav?s de um gene metab?lico
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Henriques, Andreia Filipa Pereira. "Caracterização da interação HipAB na Shewanella oneidensis MR1." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11775.
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Mestrado em BioquímicaBacterial resistance is a major issue in research related to environmental and public health, due to the ineffectiveness of antibiotics, resulting from a subpopulation of bacterial cells entering a dormant state. Multiple studies revealed that toxin-antitoxin systems are involved in such bacterial persistence. An example of such a toxin-antitoxin system is the HipAB complex, where HipA, and its cognate antitoxin are intimately related. HipB is very unstable and it is prone to degradation by proteases (e.g. Lon protease), leaving HipA exerting its toxic effect on cells. To study the conformations and interactions from HipAB in Shewanella oneidensis, it was necessary to overexpress and purify the proteins and to perform cross linking reactions which were analysed by mass spectrometry. The cross linking reactions were performed with BS3 (Bis[sulfosuccinimidyl] suberate), an in solution cross linker, tested at different concentrations (0.5mM, 1mM, 2mM) to find more efficient reaction conditions. By SDS-PAGE analysis it was possible to conclude that the best cross linker concentration is the highest tested. Furthermore, some predictions from possible intra- and intermolecular binding sites were made, unfortunately it was only possible to identify an interaction between HipA(143) and HipA(264).
A resistência bacteriana é um ponto importante de estudo em investigação relacionado com o ambiente e a saúde pública, devido à ineficiência dos antibióticos, que resulta de uma subpopulação de células bacterianas que entram num chamado estado dormente. Diversos estudos indicam que os sistemas toxina-antitoxina estão envolvidos nessa persistência bacteriana. Um exemplo de um sistema toxina-antitoxina é o complexo HipAB, em que a HipA e a sua respetiva antitoxina estão intimamente relacionadas. HipB é muito instável e propenso à degradação por proteases (por exemplo: Lon protease), deixando a HipA a exercer o seu efeito tóxico nas células, Para estudar as conformações e interações da HipAB na Shewanella oneidensis, foi necessário sob expressar e purificar as proteínas e promover as reações de cross linking que foram analisadas por espectrometria de massa. A reações de cross linking foram realizadas usando o BS3 (Bis[sulfosuccinimidyl] suberate), um cross linker in solution, testado a diferentes concentrações (0.5mM, 1mM, 2mM) para encontrar as condições de reação mais eficientes. Pelas análises de SDS-PAGE foi possível concluir que a melhor concentração de cross linker foi a mais alta testada. Para além disso, foram feitas algumas previsões de possíveis sítios de ligação, intra- ou intermolecular, no entanto só foi possível identificar uma das interações entre a HipA(143) com a HipA(264).
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Revesz, Erika. "Solubility and Stability of Scorodite and Adsorbed and Coprecipitated Arsenical 6-line Ferrihydrite in the Presence of Shewanella putrefaciens CN32 and Shewanella sp. ANA-3." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32185.
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Mining and mineral processing generate a wide range of As-rich minerals, including scorodite (FeAsO4•2H2O), and arsenical ferrihydrite, which are common secondary minerals found in mine tailings. Scorodite and arsenical ferrihydrite are relatively stable under a wide range of physico-chemical conditions which makes them suitable arsenic sinks in mining environments. However, bacteria can reduce these minerals and release arsenic into the aqueous environment. Two dissimilatory iron and arsenic reducing bacteria, Shewanella sp. ANA-3 and Shewanella putrefaciens CN32, were used to investigate their effects on the reductive dissolution of scorodite and arsenical 6-line ferrihydrite in a chemically defined medium containing low phosphate concentrations representative of the natural environment. Analysis of the aqueous phase of all biotic reduced samples found mainly As(III), the more toxic form of As, while very little As(V) was reduced in the abiotic samples. Solid state analysis of the scorodite biotic post-reduction minerals identified scorodite, biogenic Fe(II)-As(III) compounds, parasymplesite and tooeleite, while in the biotic reduced arsenical six-line ferrihydrite, biogenic Fe(II)-As(III) compounds, hematite, akaganeite and unconfirmed magnetite were identified as secondary reduction products. Results from this research add to the body of literature on As and Fe biogeochemistry and provide very useful information for future assessments of the long term stability of As-rich minerals.
L’activité minière et la transformation du minerai génèrent divers minéraux riches en arsenic, tels la scorodite (FeAsO4•2H2O) et la ferrihydrite riche en arsenic, lesquels sont des minéraux secondaires communs des résidus miniers. Comme la scorodite et la ferrihydrite riche en arsenic sont relativement stables sous une grande gamme de conditions physico-chimiques, ces minéraux peuvent potentiellement être utilisés pour stocker de façon permanente l’arsenic dans les environnements miniers. Cependant, certaines bactéries peuvent réduire ces minéraux, ce qui entraine la solubilisation de l’arsenic. Deux bactéries capables de réduire l’arsenic et le fer, soit Shewanella sp. ANA-3 et Shewanella putrefaciens CN32, ont été utilisées afin de déterminer leurs effets sur la réduction microbienne de la scorodite et de la ferrihydrite riche en As dans un milieu de culture contenant de faibles concentrations de phosphate. Les analyses de la phase aqueuse ont démontré que dans tous les systèmes biotiques, As(V) a été réduit en As(III), alors que dans les systèmes contrôles abiotiques, peu de As(V) a été réduit. L’analyse des minéraux secondaires présents à la fin réduction dans les systèmes biotiques contenant de la scorodite indique que la scorodite est encore présente, ainsi que des composés organiques riches en Fe(II) et As(III), de la parasymplésite et de la tooéleite, alors que dans les systèmes biotiques contenant de la ferrihydrite riche en As, des composés riches en Fe(II) et en As(III), de l’hématite, de l’akaganéite et de la magnétique ont été identifiés comme minéraux secondaires. Les résultats de cette étude enrichissent la littérature sur le cycle biogéochimique du Fe et de As et fournissent de l’information importante pour l’évaluation de la stabilité à long terme de minéraux riches en As.
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Fulayfil, Nada Rashid. "Characterization of LuxA of novel strains of the genus Shewanella." FIU Digital Commons, 1994. http://digitalcommons.fiu.edu/etd/3425.
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Bioluminescence is a trait observed among different genera and families of bacteria. In this study part of the luxA gene was characterized from the new MS isolates and compared to luxA of other bacteria. The polymerase chain reaction (PCR) was used to amplify a fragment of the luxA gene of strain MS32 and Vibrio harveyi. These fragments were used as probes in hybridization experiments with luminous and nonluminous bacteria. The results from these experiments suggest that some nonluminous species may possess lux like regions in their chromosomal DNA and that luxA probes can demonstrate species identity. The MS32 luxA fragment was also sequenced and used in a phylogenetic analysis to identify the taxonomic affinities of MS strains. It was found that MS1 and MS32 were closely related, however, Shewanella hanedai was not. Thus there was a concordance between the phenotypic and genotypic approaches, which will help in establishing a consistent taxonomic affinity between these bacteria.
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Wang, Hui. "The physiological diversity of Shewanella oneidensis : a metabolic approach." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506279.
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Shewanella oneidensis MR-1 is an important model Fe(III)-reducing bacterium due to its unique metabolic flexibility including the ability to reduce a wide range of organic and inorganic substrates. The recent availability of the complete genome sequence for this organism together with the application of cutting edge postgenomic techniques are leading to a detailed understanding of the physiology of this organism under a wide range of environmental conditions. In this thesis, a multidisciplinary approach combining microbiology, electron microscopy, spectroscopy and analytical chemistry has been used to dissect the physiology of S. oneidensis MR-1 under a range of growth conditions, and the interactions of the organism with redox active organics and metals has been explored.
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Pealing, Sara L. "Flavocytochrome C from Shewanella putrefaciens : a soluble fumarate reductase." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/15615.
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Flavocytochrome c from the Gram-negative bacterium Shewanella putrefaciens is a soluble, periplasmic fumarate reductase induced under anaerobic conditions. In order to study this protein the entire structural gene was cloned and sequenced, along with some surrounding sequence. Analysis of the cloned gene indiciates that flavocytochrome c consists of 571 amino acids preceded by a putative periplasmic signal sequence of 25 amino acids. Flavocytochrome c appears to consist of two domains: -a cytochrome domain consisting of approximately the first 117 amino acids containing the four c-type haem binding motifs (CxxCH), which shows some similarity to a tetrahaem cytochrome from the purple phototrophic bacterium H-1-R -a flavin domain comprising the remainder of the protein which shows significant similarity to the flavoprotein subunits of the family containing fumarate reductases and succinate dehydrogenases from other organisms. For example, it shows 26% identity to the flavoprotein subunit of Escherichia coli fumarate reductase at the amino acid level, including all the active site residues which have been identified. Three additional open reading frames have been identified in the regions flanking the fcc gene. ORF2, is situated -400bp downstream of fcc and reads in the same direction as the fcc gene. The deduced amino acid sequence of this open reading frame is 135 amino acid residues in length and shows some limited sequence similarity for FrdD, one of the two subunits of E. coli fumarate reductase which serves to anchor the enzyme to the membrane and is involved in electron transport to the catalytic domain. Since flavocytochrome c is a soluble enzyme, the product of ORF2 does not appear to be a membrane anchor for this enzyme, however a role in electron transport to flavocytochrome c has not been ruled out. ORFI and ORF3 both read in the opposite direction from flavocytochrome c and neither is completely contained on the cloned fragment. Searching of the databases has revealed no apparent homologues for either of these reading frames.
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Bose, Saumyaditya. "Bioreduction of Hematite Nanoparticles by Shewanella oneidensis MR-1." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/30189.
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A dissertation is presented on the bioreduction of hematite (α-Fe2O3) nanoparticles. The study shows that an alternative extracellular electron transfer mechanism other than the classical 'direct-contact' mechanism may be simultaneously employed by Shewanella oneidensis MR-1 during solid-phase metal reduction. This conclusion is supported by analysis of the bioreduction kinetics of hematite nanoparticles coupled with microscopic investigations of cell-mineral interactions. The reduction kinetics of metal-oxide nanoparticles were examined to determine how S. oneidensis utilizes these environmentally-relevant solid-phase electron acceptors. Nanoparticles involved in geochemical reactions show different properties relative to larger particles of the same phase, and their reactivity is predicted to change as a function of size. To demonstrate these size-dependent effects, the surface area normalized reduction rates of hematite nanoparticles by S. oneidensis MR-1 with lactate as the sole electron donor were measured. As evident from whole cell TEM analysis, the mode of nanoparticle adhesion to cells is different between the more aggregated, pseudo-hexagonal to irregular shaped 11 nm, 12 nm, 99 nm and the less aggregated 30 nm and 43 nm rhombohedral particles. The 11 nm, 12 nm and 99 nm particles show less cell contact and coverage than the 30 nm and 43 nm particles but still show significant rates of reduction. This leads to the provisional speculation that S. oneidensis MR-1 employs a pathway of indirect electron transfer in conjunction with the direct-contact pathway, and the relative importance of the mechanism employed depends upon aggregation level and the shape of the particles or crystal faces exposed. In accord with the proposed increase in electronic band-gap for hematite nanoparticles, the smallest particles (11 nm) exhibit one order of magnitude decrease in reduction when compared with larger (99 nm) particles, and the 12 nm rates fall in between these two. This effect may also be due to the passivation of the mineral and cell surfaces by Fe(II), or decreasing solubility due to decrease in size.Ph. D.
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Hansen, Jhoanne [UNESP]. "Clonagem, expressão e caracterização de duas lipoxigenases de Shewanella woodyi." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/103881.
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000737473.pdf: 4424353 bytes, checksum: 83d4de348d8c1081e547b22ff3eab4d2 (MD5)Lipoxigenases são enzimas que catalizam a oxido-redução de ácidos graxos poliinsaturados que contém em sua estrutura um ou mais grupos cis 1,4- pentadieno, produzindo hidroperóxidos através da incorporação de um oxigênio molecular. Durante anos a presença de lipoxigenase foi considerada exclusivamente eucariótica, presente em mamíferos, plantas, pequenos invertebrados marinhos e fungos. A função biológica dessas enzimas tem sido amplamente estudada. Porém, pouco tem sido descrito em organismos procariotos. O presente estudo teve por objetivos clonar e caracterizar bioquimicamente duas lipoxigenases de Shewanella woodyi ATCC 51908, caracterizar os produtos de reação destas enzimas e realizar um estudo filogenético e estrutural, comparando-as com lipoxigenases de eucariotos e procariotos. Parâmetros enzimáticos dessas enzimas foram descritos. A influência do pH e temperatura na atividade catalítica foram estudadas. Também foi determinado a preferência por substrato e o efeito da adição de vários íons divalentes que podem interferir na atividade catalítica. A enzima SWPrecLox de S. woodyi apresentou temperatura e pH ótimos de 31ºC e 8,0, respectivamente. Demonstrou afinidade por ácido linoleico, com uma Km de 0,47 mM e Vmax de 2,78 mmols min-1 mg-1. A enzima SWAracLOX teve ácido araquidônico como substrato preferente, com valores de Km 0,20 mM e Vmax 1,6 mmols min-1 mg-1. Atividade ótima foi alcançada com 27ºC e pH 7,0. A partir das estruturas moleculares das lipoxigenases de Plexaura homomalla e Pseudomonas aeruginosa, foram criados hipotéticos modelos estruturais de SWPrecLOX e SWAracLOX.
Lipoxygenases are enzymes that catalyze the oxido-reduction of polyunsaturated fatty acids in their structure that contains one or more groups cis 1,4- pentadiene, producing hydroperoxides from the incorporation of molecular oxygen. For years, the presence of lipoxygenases was considered a eukaryotic feature, present in mammals, plants, small marine invertebrates and fungi. The present study aimed to clone and characterize biochemically two lipoxygenases from Shewanella woodyi ATCC 51908, characterize the reaction products of these enzymes and conduct a phylogenetic and structural analysis, comparing them with eukaryotes and prokaryotes lipoxygenases. The biological function of these lipoxygenases has been widely studied. However, only few have been described in prokaryotes. Enzymatic parameters of these enzymes have been described. The influence of the pH and the temperature on the catalytic activity has been studied. Also has been studied the substrate preference and the effect of the addition of several divalent cations that can enhance or eliminate the catalytic activity. The enzyme SWPrecLox of S. woodyi showed temperature and pH optimum were 31 ºC and 8,0, respectively. Demonstrated substrate affinity for linoleic acid, with Km 0,47 mM and Vmax 2,78 mmols min-1 mg-1. The enzyme SWAracLox has arachidonic acid as preferred substrate, with Km 0,20 mM and Vmax 1,6 mmols min-1 mg-1. Optimum activity was reached at 27 ºC and pH 7,0. From the molecular structures of lipoxygenase Plexaura homomalla and Pseudomonas aeruginosa, were created a hypothetical structural model of the SWPrecLox and SWAracLox.
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Wade, Roy Jr. "A genetic system for studying uranium reduction by Shewanella putrefaciens." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/25304.
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Blakeney, Michael. "Effects of respiratory conditions on cytochrome expression in Shewanella Putrefaciens." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/25374.
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Norman, Michael. "Role of cysteine in MtrC-flavin interactions of Shewanella oneidensis." Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/69368/.
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Many microorganisms can utilise a wide range of terminal electron acceptors, including solid minerals in the environment. Shewanella oneidensis is a well studied model for extracellular electron transfer with many of its biochemical pathways the subject of investigation. S. oneidensis utilises c-type cytochromes embedded in its outer membrane to link the oxidation of carbon sources to the reduction of extracellular terminal electron acceptors. Although the MtrCAB complex is known to be the primary pathway by which electrons, originating in the reduced menaquinol pool, can be conducted across the bacterial outer membrane and to extracellular terminal electron acceptors, the exact mechanism by which electrons are transferred from MtrC to electron acceptors remains unclear. MtrA and MtrC are decaheme cytochromes that form wire-like molecular pathway for electrons to be conducted across the bacterial membrane. MtrB is a porin that allows close contact between the periplasmic MtrA and the extracellular facing MtrC. Flavin molecules, secreted by S. oneidensis, have been shown to interact with MtrC either forming cofactor like associations with the protein (forming a flavocytochrome) or functioning as soluble electron shuttles transiently interacting with the protein. The evidence for each mechanism may be dependant on the redox state of a conserved disulphide bond in domain III of MtrC. Chemical reduction of this bond allows formation of a MtrC-flavin bound flavocytochrome form of MtrC. This form could react better with minerals to dictate the mechanism of electron transfer. Mutations made to mtrC resulted in the substitution of the cysteine disulphide residues to alanine residues in the MtrC amino acid sequence. Growth studies showed S. oneidensis expressing these MtrC variants experienced extended lag phases when growing under aerobic conditions. This was shown to be caused by cytotoxic levels of hydrogen peroxide, generated from reduction of molecular oxygen, accumulating around the bacterial cells. Protein studies implicated stronger interactions between FMN and MtrC, in disulphide disrupted variants, as the cause of increased reactive oxygen species generation. We hypothesise the disulphide bond in domain III of MtrC functions as a redox switch imparting protein level control over reactivity of MtrC in oxygen variable environments.
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Hill, Anne E. "Characterisation of cytochromes c3 and c5 from Shewanella frigidimarina NCIMB400." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/14066.
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The structural gene encoding cytochrome c5 has been cloned and sequenced, along with some surrounding sequence. The inferred amino acid sequence of the cloned gene, scyA, corresponds to a mature protein of 78 amino acids with a single haem attachment motif situated toward the N-terminal end of the protein; a methionine residue near the C-terminus serves as the sixth haem ligand. The scyA open reading frame contains a 21 amino acid N-terminal extension which is absent in purified cytochrome c5. This sequence conforms to the format of a typical periplasmic signal sequence. Two additional open reading frames were identified on analysis of the regions flanking the structural gene, neither of which is functionally related to cytochrome c5. Northern blott analysis confirmed that scyA is transcriptionally isolated. A null mutant which lacked the gene coding for cytochrome c5 was constructed. The anaerobic respiratory capacity of the resultant strain was assessed and compared to wild-type. No obvious mutant phenotype was identified. Gene disruption experiments were also used to characterise cytochrome c3. Deletion strains lacking the gene coding for cytochrome c3 (cctA) and also strains lacking both cytochrome c3 and flavocytochrome c3 were constructed. Comparison of the growth characteristics of the mutant strains with wild-type suggest the involvement of cytochrome c3 with respiratory iron (III) reduction. Ferrozine extraction experiments similarily demonstrated a decrease in iron (III) reduction activity by strains lacking the cytochrome c3 gene. In order to facilitate further study of cytochrome c5, and production of recombinant forms of the protein, an expression system was developed. Cytochrome c5 was successfully expressed in Shewanella frigidimarina NCIMB400 by using the expression vector pMMB503 which is inducible with isopropylthio-β-D-galactoside.
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Hansen, Jhoanne. "Clonagem, expressão e caracterização de duas lipoxigenases de Shewanella woodyi /." Jaboticabal, 2013. http://hdl.handle.net/11449/103881.
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Orientadora: Maria Benincasa VidottiCo-orientadora: Angeles Manresa
Banca: Ana Claudia Barana
Banca: Vanildo Luiz Del Bianchi
Banca: Mariana Carina Frigieri
Banca: Janete Apparecida Desiderio
Resumo: Lipoxigenases são enzimas que catalizam a oxido-redução de ácidos graxos poliinsaturados que contém em sua estrutura um ou mais grupos cis 1,4- pentadieno, produzindo hidroperóxidos através da incorporação de um oxigênio molecular. Durante anos a presença de lipoxigenase foi considerada exclusivamente eucariótica, presente em mamíferos, plantas, pequenos invertebrados marinhos e fungos. A função biológica dessas enzimas tem sido amplamente estudada. Porém, pouco tem sido descrito em organismos procariotos. O presente estudo teve por objetivos clonar e caracterizar bioquimicamente duas lipoxigenases de Shewanella woodyi ATCC 51908, caracterizar os produtos de reação destas enzimas e realizar um estudo filogenético e estrutural, comparando-as com lipoxigenases de eucariotos e procariotos. Parâmetros enzimáticos dessas enzimas foram descritos. A influência do pH e temperatura na atividade catalítica foram estudadas. Também foi determinado a preferência por substrato e o efeito da adição de vários íons divalentes que podem interferir na atividade catalítica. A enzima SWPrecLox de S. woodyi apresentou temperatura e pH ótimos de 31ºC e 8,0, respectivamente. Demonstrou afinidade por ácido linoleico, com uma Km de 0,47 mM e Vmax de 2,78 mmols min-1 mg-1. A enzima SWAracLOX teve ácido araquidônico como substrato preferente, com valores de Km 0,20 mM e Vmax 1,6 mmols min-1 mg-1. Atividade ótima foi alcançada com 27ºC e pH 7,0. A partir das estruturas moleculares das lipoxigenases de Plexaura homomalla e Pseudomonas aeruginosa, foram criados hipotéticos modelos estruturais de SWPrecLOX e SWAracLOX.
Abstract: Lipoxygenases are enzymes that catalyze the oxido-reduction of polyunsaturated fatty acids in their structure that contains one or more groups cis 1,4- pentadiene, producing hydroperoxides from the incorporation of molecular oxygen. For years, the presence of lipoxygenases was considered a eukaryotic feature, present in mammals, plants, small marine invertebrates and fungi. The present study aimed to clone and characterize biochemically two lipoxygenases from Shewanella woodyi ATCC 51908, characterize the reaction products of these enzymes and conduct a phylogenetic and structural analysis, comparing them with eukaryotes and prokaryotes lipoxygenases. The biological function of these lipoxygenases has been widely studied. However, only few have been described in prokaryotes. Enzymatic parameters of these enzymes have been described. The influence of the pH and the temperature on the catalytic activity has been studied. Also has been studied the substrate preference and the effect of the addition of several divalent cations that can enhance or eliminate the catalytic activity. The enzyme SWPrecLox of S. woodyi showed temperature and pH optimum were 31 ºC and 8,0, respectively. Demonstrated substrate affinity for linoleic acid, with Km 0,47 mM and Vmax 2,78 mmols min-1 mg-1. The enzyme SWAracLox has arachidonic acid as preferred substrate, with Km 0,20 mM and Vmax 1,6 mmols min-1 mg-1. Optimum activity was reached at 27 ºC and pH 7,0. From the molecular structures of lipoxygenase Plexaura homomalla and Pseudomonas aeruginosa, were created a hypothetical structural model of the SWPrecLox and SWAracLox.
Doutor
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Shah, Maia Kierann. "Surface interaction characterisation of microbial fuel cell organism Shewanella oneidensis." Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa42293.
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In order to develop MFCs to their full potential, the mechanisms by which organisms such as S. oneidensis transfer electrons extracellularly need to be researched and understood, and key to this are the physical and chemical interactions between the cell surface and the surrounding environment, including other cells, minerals and MFC-relevant substrates. The research presented here characterises the physical interactions of anaerobically grown S. oneidensis MRl under varying chemical conditions, using aerobically grown cells in identical experiments for comparison. An array of experimental methods are used, including techniques for estimating cell concentration for growth profiles, zeta-potential of cells in solution, and Atomic Force Microscopy imaging of cells in different growth phases. A novel method using Surface Plasmon Resonance is used to quantify the kinetics of binding of cells to surfaces approximating MFC electrodes. This method is assessed for suitability and reviewed as a potential answer to other research problems based on cell-device interfaces. Finally, novel force spectroscopy using custom-made mineral probes is used to gather mechanical data about cells of S. oneidensis MR-1 and to quantify the interaction of cells with iron oxide and graphite. The results show the differences in growth profiles between aerobically and anaerobically grown cells. Different results were also seen for aerobically grown and anaerobically grown cells in preliminary SPR studies using poly-L-lysine, and in the force spectroscopy results including adhesion force and Young's moduli. The effects of pH and salinity on cell surface interaction were investigated using measured isoelectric points from the zeta-potential studies as a guide and found to change the measured values of Young's modulus, and the maximum change in SPR response, for both types of cell. The demonstrable effects of ambient chemistry on cell-cell and cell-surface interaction provide a reference point for bio-device design with the potential for multi-organism devices utilising the multiple electron transfer pathways of S. oneidensis MRl. The use of SPR for real time measurement of whole-cell binding to electrode-approximating surfaces and the resultant interaction kinetics is established as a novel, repeatable and accessible way of investigating cell-surface interaction.
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Fennessey, Christine Michelle. "A novel mode of bacterial respiration: iron solubilization prior to electron transfer." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37257.
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Microbial iron respiration contributes significantly to the biogeochemical cycling of metals and may be one of the earliest respiratory processes to have evolved on early earth. Metal-respiring microbes also hold great potential for use in microbial fuel cells for the generation of "green" energy and for remediation of radionuclides in contaminated environments. Despite its significance in global metal cycling processes, the molecular mechanism of Fe(III) respiration has yet to be determined. Unlike many other terminal electron acceptors, Fe(III) is a solid at circumneutral pH and, therefore, cannot come into direct contact with the microbial inner membrane: the site of terminal electron transfer in gram-negative bacteria. It is postulated that metal-respiring organisms have developed alternate strategies for the reduction of solid iron. One such strategy involves the production of an Fe(III)-solublizing ligand by the metal-respiring bacteria which solubilizes the Fe(III) prior to respiration, rendering the metal more easily accessible to the Fe(III) reductase complex.
In this study, the genes involved in the solubilization of Fe(III) by the gram-negative dissimilatory metal reducing bacteria Shewanella oneidensis MR-1 were determined using random mutagenesis to generate mutations in the wild-type genome and high-throughput square-wave voltammetry to screen for the attenuation of Fe(III) production in the mutants. Two mutants unable to solubilize Fe(III) were identified and designated d29 and d64. After mutation complementation analysis, it was determined that the point mutations were both located in type II secretion genes: gspG and gspE respectively, indicating that the type II secretion system is required for Fe(III) solubilization prior to respiration.
It was also hypothesized that the ligand produced for Fe(III) solubilization during dissimilatory Fe(III) respiration was a siderophore: a small Fe(III)-chelating molecule produced by the cells for the assimilation of Fe(III) for growth. A siderophore biosynthesis gene (SO3031) and a siderophore ferric reductase gene (SO3034) were deleted in frame and the resultant mutants screened to determine whether they were capable of Fe(III) solubilization and reduction during anaerobic Fe(III) respiration. Both mutants retained Fe(III) solubilization and reduction activity, indicating that the siderophore Fe(III) assimilatory system is distinct from the Fe(III) solubilization system utilized during Fe(III) respiration.
The work presented here is significant in that it describes a rapid screening method for identifying Fe(III) solubilization mutants, reports on the involvement of the type II secretion system in Fe(III) solubilization during iron respiration, and finally demonstrates that a dissimilatory metal reducing bacteria synthesizes and secretes Fe(III)-chelating molecules which are distinct from Fe(III)-siderophores.
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Guinetti-Ortiz, Katia, Alejandra Bocanegra-Jesús, and de la Torre-Del Carpio Andrea Gómez. "Osteomielitis por Shewanella putrefaciens: reporte de caso y revisión de literatura." Medwave, 2016. http://hdl.handle.net/10757/622343.
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Shewanella putrefaciens is a Gram-negative bacillus and marine pathogen that rarely causes disease in humans. We report a case of osteomyelitis by this organism in a 48-year-old male patient, who presented with pain and erythema of the right foot that was initially diagnosed as cellulitis and did not revert despite treatment. He was transferred to Lima where osteomyelitis was diagnosed and started on empirical treatment with partial regression. A biopsy and culture of the compromised area found S. putrefaciens. The infection was treated according to the antibiotic sensitivity profile of the pathogen. S. putrefaciens infection represents a rare opportunistic infection of devitalized or exposed areas of the body. It is associated with residence in coastal areas and commonly affects the skin and soft tissues. Exceptional cases of osteomyelitis have been reported, but this is the first that involves the metatarsal bones.
Shewanella putrefaciens es un bacilo Gram negativo, patógeno marino que rara vez ocasiona enfermedad en humanos. Se presenta un caso de osteomielitis por este microorganismo en un paciente varón de 48 años, procedente de Chimbote. Presentó dolor y eritema en el pie derecho, inicialmente diagnosticado como celulitis, pero que no revirtió pese al tratamiento. Fue transferido a Lima donde se diagnosticó osteomielitis e inició tratamiento empírico con escasa mejoría. Por ello, se realizó una biopsia y cultivo de la zona comprometida, el metatarso, en el cual se aisló Shewanella putrefaciens. Se trató de acuerdo al perfil de sensibilidad. La infección por Shewanella putrefaciens representa una rara infección oportunista, que se localiza en áreas desvitalizadas o expuestas del cuerpo. Se asocia a vivir en zonas costeras, afectando comúnmente piel y tejidos blandos. Se han reportado casos excepcionales de osteomielitis. Este es el primero que involucra metatarso.
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Field, Sarah J. "Identification and characterisation of bacterial multiheme cytochromes implicated in Fe (III) respiration." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327449.
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Sherwood, Mackenzie A. Firer. "Electron transfer in multiheme cytochromes of Shewanella oneidensis MR-1: CymA and the dissimilatory metal reduction pathway." Thesis, Boston University, 2012. https://hdl.handle.net/2144/32061.
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Thesis (Ph.D.)--Boston UniversityPLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
Shewanella oneidensis is a facultative, gram-negative microbe that, in the absence of oxygen, can use a wide variety of terminal electron acceptors including iron, manganese, uranium, nitrite, nitrate, sulfate, fumarate, and DMSO. The anaerobic versatility is believed to be the result of a highly branched electron transfer pathway involving many redox-active proteins. Shewanella is capable of dissimilatory metal reduction (DMR) of insoluble iron and manganese oxides, in which electrons are transferred from the cell's interior to its exterior. Several multiheme c -type cytochromes comprise a pathway for this electron transfer. These cytochromes, specifically the tetraheme protein, CymA, and the decaheme protein, MtrA, are the primary focus of this thesis. The current model of electron transfer indicates that electrons originate in the cytoplasmic membrane from the menaquinol pool, and are transferred into the periplasm by CymA. From here the pathway branches and electrons are transferred into several potential periplasmic targets, including MtrA. MtrA may then transfer electrons directly or indirectly to MtrC and OmcA, which have been shown to reduce exogenous electron acceptors such as iron oxides. Recently, it has been suggested that MtrA and MtrC dock with 13-barrel protein, MtrB and transfer electrons through the porin sheath. Here, the DMR pathway has been studied with respect to four aims: (1) purification and characterization of the multiheme cytochromes through the use of non-catalytic protein film voltammetry (PFV), (2) structural analysis of MtrA by small angle X-ray scattering (SAXS), (3) investigation of protein-protein interactions via catalytic PFV and anaerobic affinity chromatography, and (4) exploration of heme cofactor function within the tetraheme cytochrome, CymA and MtrA by characterizing heme knockout mutants of the two proteins. We demonstrate that these proteins interact to form an electron transfer pathway from the cytoplasm to terminal electron acceptors on the outside of the cell through a "wire" of heme cofactors. Additionally, the data support the model that MtrA can span a large portion of the peri plasmic space to act as an intermediary by accepting electrons from CymA and subsequently docking with MtrB to transfer electrons to MtrC.
2031-01-02
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Burns, Justin Lee. "Molecular mechanisms of microbial iron respiration by Shewanella oneidensis MR-1." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33825.
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Metal-respiring bacteria occupy a central position in a variety of environmentally important processes including the biogeochemical cycling of metals and carbon, biocorrosion of steel surfaces, bioremediation of radionuclide-contaminated aquifers, and electricity generation in microbial fuel cells. Metal-respiring bacteria are presented, however, with a unique physiological challenge: they are required to respire anaerobically on electron acceptors (e.g., Fe(III) oxides, elemental sulfur) that are highly insoluble at circumneutral pH and unable to enter the cell and contact inner membrane-localized respiratory systems. To overcome these physiological problems, metal-respiring bacteria are postulated to employ a variety of novel respiratory strategies not found in other bacteria, including 1) direct enzymatic reduction at the cell surface, 2) electron shuttling between the cell and metal surfaces, and 3) metal solubilization by bacterially-produced organic ligands followed by respiration of the soluble organic-metal complexes. This work highlights my latest findings on the genetic and enzymatic mechanism of metal respiration by Shewanella oneidensis, a facultative anaerobe ubiquitous to redox-stratified natural waters and sediments.
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Haller, Carolyn A. "Dissimilatory FE(III) reduction by Shewanella putrefaciens : biochemical and genetic analysis." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/25616.
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Pitts, Katy Elizabeth. "Expression and characterisation of Shewanella oneidensis multihaem cytochromes in Escherichia coli." Thesis, University of East Anglia, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410137.
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Ong, Wai, Trang Vu, Klaus Lovendahl, Jenna Llull, Margrethe Serres, Margaret Romine, and Jennifer Reed. "Comparisons of Shewanella strains based on genome annotations, modeling, and experiments." BioMed Central, 2014. http://hdl.handle.net/10150/610105.
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BACKGROUND:Shewanella is a genus of facultatively anaerobic, Gram-negative bacteria that have highly adaptable metabolism which allows them to thrive in diverse environments. This quality makes them an attractive bacterial target for research in bioremediation and microbial fuel cell applications. Constraint-based modeling is a useful tool for helping researchers gain insights into the metabolic capabilities of these bacteria. However, Shewanella oneidensis MR-1 is the only strain with a genome-scale metabolic model constructed out of 21 sequenced Shewanella strains.RESULTS:In this work, we updated the model for Shewanella oneidensis MR-1 and constructed metabolic models for three other strains, namely Shewanella sp. MR-4, Shewanella sp. W3-18-1, and Shewanella denitrificans OS217 which span the genus based on the number of genes lost in comparison to MR-1. We also constructed a Shewanella core model that contains the genes shared by all 21 sequenced strains and a few non-conserved genes associated with essential reactions. Model comparisons between the five constructed models were done at two levels - for wildtype strains under different growth conditions and for knockout mutants under the same growth condition. In the first level, growth/no-growth phenotypes were predicted by the models on various carbon sources and electron acceptors. Cluster analysis of these results revealed that the MR-1 model is most similar to the W3-18-1 model, followed by the MR-4 and OS217 models when considering predicted growth phenotypes. However, a cluster analysis done based on metabolic gene content revealed that the MR-4 and W3-18-1 models are the most similar, with the MR-1 and OS217 models being more distinct from these latter two strains. As a second level of comparison, we identified differences in reaction and gene content which give rise to different functional predictions of single and double gene knockout mutants using Comparison of Networks by Gene Alignment (CONGA). Here, we showed how CONGA can be used to find biomass, metabolic, and genetic differences between models.CONCLUSIONS:We developed four strain-specific models and a general core model that can be used to do various in silico studies of Shewanella metabolism. The developed models provide a platform for a systematic investigation of Shewanella metabolism to aid researchers using Shewanella in various biotechnology applications.
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Gordon, Euan H. J. "The physiological role of a novel flavocytochrome c from Shewanella putrefaciens." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/14921.
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Flavocytochrome c (Fcc) is a novel, soluble periplasmic fumarate reductase from the Gram-negative bacterium Shewanella putrefaciens. A null mutant (Δfcc) which lacked the gene coding for the Fcc was constructed. The resultant strain was devoid of fumarate reductase activity and could not grow on fumarate as the sole terminal electron acceptor. Complementation of this mutation with recombinant Fcc restored the ability to grow anaerobically with fumarate. No other phenotype could be found for the Δfcc strain. This work demonstrates that flavocytochrome c is essential for fumarate respiration and furthermore is the sole terminal reductase for fumarate respiration. The fcc null mutant also allowed the expression of recombinant forms of fcc coding for the individual domains of the protein. The in vivo interaction between the haem and flavin domains of Fcc was investigated by expressing recombinant forms of the genes coding for these domains in the same cell. This indicated that the tether between the two domains, while not absolutely essential, was important for wild-type enzyme function. Studies using lacZ reporter genes fused to the fcc promoter demonstrated that the fcc gene is regulated primarily at the level of transcription and is regulated hierarchically in response to the redox potential of terminal electron acceptors. Regions of the fcc promoter sequence important to regulation of the fcc gene were identified by deletion analysis. The succinate dehydrogenase operon from S. putrefaciens was sequenced. The inferred amino acid sequences of the flavoprotein, and iron/sulphur subunits showed high sequence identity (77%) with the corresponding subunits from Escherichia coli succinate dehydrogenase.
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Baeza, Lara Nicolás. "Caracterización de las vesículas de membrana de Shewanella vesiculosa M7(T)." Doctoral thesis, Universitat de Barcelona, 2021. http://hdl.handle.net/10803/673929.
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La presente Tesis Doctoral se enmarca en el proyecto CTQ2014-59632-R concedido por el ministerio de economía y competitividad al grupo de investigación. El trabajo se ha centrado en caracterizar las vesículas de membrana (VM) de Shewanella vesiculosa M7T y explorar potenciales aplicaciones. Esta bacteria gramnegativa procedente de la Antártida fue descrita por nuestro grupo y ha sido usada como cepa modelo por la gran cantidad de VM que forma. Actualmente se acepta que las bacterias gramnegativas pueden formar distintos tipos de VM y que existen diferentes mecanismos de vesiculación implicados. A su vez, la formación de vesículas depende de diversos factores fisiológicos y ambientales. Todo ello, provoca que las VM de una población bacteriana puedan ser diversas en cuanto a su contenido y funciones, lo que les permite actuar en diversos procesos fisiológicos bacterianos. En estudios anteriores se demostró que S. vesiculosa M7T produce vesículas de membrana externa (VME) ya descritas y un nuevo tipo de vesículas que se denominaron vesículas de membrana externa e interna (VME-I) ya que se formaban por evaginación conjunta de ambas membranas y podían arrastrar contenido del citoplasma bacteriano como DNA.
Las VME-I han suscitado un notable interés científico, de modo que un objetivo principal de esta tesis ha sido intentar separarlas del resto de VM de S. vesiculosa M7T para poder estudiar su contenido y su mecanismo de formación. La separación se ha conseguido mediante sorting por citometría de flujo de alta resolución, pero no en cantidades suficientes para poder trabajar con ellas. De todos modos, los estudios de citometría de flujo, junto con los de microscopía electrónica de transmisión y de crio-microscopía electrónica, han confirmado que la cantidad y tipo de vesículas producidas por S. vesiculosa M7T varía en función de su fase de crecimiento. Los diferentes ácidos nucleicos presentes en las VM han sido objeto de estudio en los últimos años con el objetivo de entender posibles mecanismos de regulación intercelular o de transferencia horizontal génica. En este trabajo, la secuenciación del genoma de S. vesiculosa M7T y del DNA contenido en sus VM, han confirmado que el genoma de la cepa estaba completamente representado en los fragmentos contenidos en las VM de cultivos de 24 y 48 horas. Además, permitió identificar la presencia de un fago lisogénico insertado en el genoma de la cepa.
Por otro lado, a las 24 h de cultivo se han podido observar procesos de muerte celular programada (PCD). Este hecho, junto la presencia del genoma completo en los fragmentos de las VM, la identificación de un fago lisogénico y las imágenes de microscopía electrónica, han confirmado que en los cultivos de S. vesiculosa M7T se activa a las 24 horas, un proceso de lisis celular de una fracción de la población. Esta lisis es similar a la descrita como “lisis celular explosiva” por otros autores y da lugar a la formación de VME y VME-I mediante la recircularización de fragmentos de membranas
de células explosionadas, lo cual confiere una gran heterogeneidad a la población de VM de S. vesiculosa M7T. Por tanto, podemos decir que existen dos mecanismos de formación de VME-I, el ya descrito por el grupo de extrusión conjunta de las dos membranas y el de la simple recircularización de fragmentos de membrana externa e interna generados en un proceso de lisis celular mediada por un fago.
Las VM de algunas bacterias gramnegativas pueden contener otros componentes del citoplasma como ATP. Tanto las VM como el ATP extracelular (eATP) se han relacionado con la formación de biofilms. En este trabajo se ha estudiado la posible correlación entre la presencia de eATP en las VM y la capacidad de formar biofilms por parte de cepas antárticas descritas anteriormente por nuestro grupo de investigación. En la mayoría de las cepas analizadas, no se observó correlación entre estos estos factores estudiados. Solamente S. vesiculosa M7T secretó altos niveles de eATP y sus VM provocaron un aumento significativo en la velocidad y la cantidad de biofilm formado. También se observó que una gran parte del eATP está contenido dentro de las VM, protegido de la degradación enzimática, y que el ATP influye en la formación del biofilm.
En relación al estudio de aspectos aplicados de las vesículas de S. vesiculosa M7T, se ha analizado la actividad bactericida de las VM de S. vesiculosa M7T frente a diversas cepas gramnegativas y grampositivas, tanto cepas procedentes de la Antártida como cepas de interés clínico. Las vesículas sólo han inhibido el crecimiento de bacterias grampositivas por su capacidad de degradar el peptidoglicano de dichas cepas, probablemente por la presencia de enzimas de tipo peptidoglicanasas. Sin embargo, la heterogeneidad y complejidad de las mezclas de VM han dificultado la reproducibilidad de los resultados, descartando su uso como antibióticos.
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Eubanks, Sean Gilrea. "Development and application of a rapid screening technique for the isolation of selernium reduction-deficient mutants of Shewanella putrefaciens." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/25636.
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Wee, Seng Kew. "Novel pathway for microbial FE(III) reduction: electron shuttling through naturally occurring thiols." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53406.
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The g-proteobacterium Shewanella oneidensis MR-1 reduces a wide range of terminal electron acceptors, including solid Fe(III) oxides. Pathways for Fe(III) oxide reduction by S. oneidensis include non-reductive (organic ligand-promoted) solubilization reactions, and either direct enzymatic, or indirect electron shuttling pathways. Results of the present study expand the spectrum of electron acceptors reduced by S. oneidensis to include the naturally occurring disulfide compounds cystine, oxidized glutathione, dithiodiglycolate, dithoidiproponiate and cystamine. Subsequent electron shuttling experiments demonstrated that S. oneidensis employs the reduced (thiol) form of the disulfide compounds (cysteine, reduced glutathione, mercaptoacetate, mercaptopropionate, and 2-nitro-5-thiobenzoate, cystamine) as electron shuttles to transfer electrons to extracellular Fe(III) oxides. The results of the present study indicate that microbial disulfide reduction may represent an important electron-shuttling pathway for electron transfer to Fe(III) oxides in anaerobic marine and freshwater environments.
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LE, DEN LE MOAL NADIA. "Conductance-metrie indirecte : detection des gaz bacteriens ; application au suivi des parametres de croissance de shewanella putrefaciens." Paris 11, 1995. http://www.theses.fr/1995PA114848.
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Dague, Etienne Block Jean-Claude. "Physico-chimie des interfaces bactérie - solution aqueuse." [S.l.] : [s.n.], 2006. http://www.scd.uhp-nancy.fr/docnum/SCD_T_2006_0226_DAGUE.pdf.
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Berger, Julia Warr Laurence Noël. "Hydratation des argiles gonflantes et influence des bactéries." Strasbourg : Université Louis Pasteur, 2008. http://eprints-scd-ulp.u-strasbg.fr:8080/925/01/BERGER_Julia_2008.pdf.
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Dale, Jason Robert. "Cytochrome c maturation and redox homeostasis in uranium-reducing bacterium Shewanella putrefaciens." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19846.
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Microbial metal reduction contributes to biogeochemical cycling, and reductive precipitation provides the basis for bioremediation strategies designed to immobilize radionuclide contaminants present in the subsurface. Facultatively anaerobic ×-proteobacteria of the genus Shewanella are present in many aquatic and terrestrial environments and are capable of respiration on a wide range of compounds as terminal electron acceptor including transition metals, uranium and transuranics. S. putrefaciens is readily cultivated in the laboratory and a genetic system was recently developed to study U(VI) reduction in this organism. U(VI) reduction-deficient S. putrefaciens point mutant Urr14 (hereafter referred to as CCMB1) was found to retain the ability to respire several alternate electron acceptors. In the present study, CCMB1 was tested on a suite of electron acceptors and found to retain growth on electron acceptors with high reduction potential (E¡¬0) [O2, Fe(III)-citrate, Mn(IV), Mn(III)-pyrophosphate, NO3-] but was impaired for anaerobic growth on electron acceptors with low E¡¬0 [NO2-, U(VI), dimethyl sulfoxide, trimethylamine N-oxide, fumarate, ×-FeOOH, SO32-, S2O32-]. Genetic complementation and sequencing analysis revealed that CCMB1 contained a point mutation (H108Y) in a CcmB homolog, an ABC transporter permease subunit required for c-type cytochrome maturation in E. coli. The periplasmic space of CCMB1 contained low levels of cytochrome c and elevated levels of free thiol equivalents (-SH), an indication that redox homeostasis was disrupted. Anaerobic growth ability, but not cytochrome c maturation activity, was restored to CCMB1 by adding exogenous disulfide bond-containing compounds (e.g., cystine) to the growth medium. To test the possibility that CcmB transports heme from the cytoplasm to the periplasm in S. putrefaciens, H108 was replaced with alanine, leucine, methionine and lysine residues via site-directed mutagenesis. Anaerobic growth, cytochrome c biosynthesis or redox homeostasis was disrupted in each of the site-directed mutants except H108M. The results of this study demonstrate, for the first time, that S. putrefaciens requires CcmB to produce c-type cytochromes under U(VI)-reducing conditions and maintain redox homeostasis during growth on electron acceptors with low E¡¬0. The present study is the first to examine CcmB activity during growth on electron acceptors with widely-ranging E¡¬0, and the results suggest that cytochrome c or free heme maintains periplasmic redox poise during growth on electron acceptors with E¡¬0 < 0.36V such as in the subsurface engineered for rapid U(VI) reduction or anoxic environments dominated by sulfate-reducing bacteria. A mechanism for CcmB heme translocation across the S. putrefaciens cytoplasmic membrane via heme coordination by H108 is proposed.
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Doherty, Mary K. "Mechanistic characterisation of flavocytochrome c3, the fumarate reductase from Shewanella frigidimarina NCIMB4000." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/13674.
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Wu, Fei. "Novel octaheme cytochrome c tetrathionate reductase (OTR) from Shewanella oneidensis MR-1." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4725.
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Octa-heme cytochrome c tetrathionate reductase (OTR) from Shewanella oneidensis MR-1 is a periplasmic protein and shows several extraordinary structural features around its active-site heme. OTR has been found able to catalyse the in vitro reduction of tetrathionate, nitrite, hydroxylamine and hydrogen peroxide. However the physiological function of this novel protein remains unknown. The subject of this thesis is the in vitro catalytic mechanism and the in vivo function of OTR. As OTR displays great similarity with bacterial penta-heme cytochrome c nitrite reductase (NrfA) in several aspects, it has been proposed that OTR might be physiologically involved in the metabolism of nitrite or other nitrogenous compounds. However kinetics assays and phenotypes studies carried out in this project suggest this is not the case. In vitro kinetic assays of the reduction of nitrite and hydroxylamine catalysed by OTR showed no significant difference in enzyme activities among the wild-type OTR and its mutant forms which have one active site residue replaced by alanine, namely OTR K153A, C64A, N61A and D150A. And the nitrite reductase activity of OTR (kcat/Km = 1.0×105 M-1•s-1) are much lower than that of NrfA (kcat/Km = ~108 M-1•s-1). These results indicate that OTR is not specifically adapted to reduce nitrite and it cannot compete for nitrite against NrfA in vivo. No phenotype difference was identified between the wild-type and the Δotr strain of Shewanella oneidensis MR-1 when nitrite or nitrate served as the sole electron acceptor. OTR appears not to be involved in the respiration or detoxification of nitrite, which is consistent with previous transcriptional and phenotype reports that involve OTR or its homologues. The in vitro tetrathionate reduction activity of OTR was unable to be reproduced in this project for unknown reasons. Although transcriptomic data from the literature suggest that OTR may be related to the metabolism of sulphur-containing compounds, kinetic and phenotype studies reveal that OTR does not directly participate in the respiration of thiosulfate, sulfite, tetrathionate, polysulfide or elemental sulphur. Cysteine 64 is a highly-conserved amino acid residue of OTR close to the active site and its side-chain sulphur atom is covalently bonded by either an oxygen or a sulphur atom as observed in the crystal structure. Such a modification is potentially important to the function of OTR. ESI mass spectroscopy results show that in native OTR the modified form is around 48 Da heavier than the unmodified form, and the MALDITOF peptide mass spectra show that the modified form could be converted into the unmodified form by reducing agent DTT. These results suggest that the modification could be a cysteine persulfide attaching an extra oxygen atom in the form of water or hydroxide anion.
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Grayer, Samuel Charles. "Studies on the bacterial potassium efflux system Kef in Shewanella denitrificans SdKef." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:4d392a8a-d80f-49b7-b350-b5a1248e099f.
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The glutathione-gated potassium efflux system (Kef) is a K+/H+ antiporter found in the majority of Gram negative pathogens, which shows potential as a novel antibiotic target. Kef plays a vital role in the protection of bacteria against toxic electrophiles through the regulation of cytoplasmic pH. Kef is inhibited by glutathione (GSH), γ L-glu-L-cys-gly, and activated by glutathione S-conjugates (GSX). Healy et al. have quantified the affinities of GSH and a range of GSX for Shewanella denitrificans Kef (SdKef). GSH was found to have a weak affinity of 900 μM, whereas the strongest GSX, tBuSG, was 400 nM. This dissertation looks to understand the potency shown by tBuSG for SdKef by exploring the binding contributions from each group of the tripeptide. Truncated analogues of tBuSG were synthesised and evaluated using a competition fluorescence assay and 1H CPMG NMR. In summary, removal of the glycine unit caused a complete loss in affinity for SdKef, whereas removing the glutamate unit resulted in a negligible loss. Interactions made by the Glu-Cys amide carbonyl oxygen, the Cys-Gly amide NH and a directional interaction of the conjugated thiol were also found to be important contributors to affinity. The information obtained during this work allowed the development of a membrane permeant, truncated analogue of tBuSG, which lacks the majority of the glutamate, for use in in vivo studies. The truncated analogue is able to activate SdKef to elicit K+ efflux, demonstrating that the majority of the glutamate is not essential for activity. Furthermore, application of this truncated analogue to Escherichia coli cells expressing the sdkef gene in a Kirby Bauer disc diffusion assay has demonstrated for the first time that small molecules activating SdKef can elicit inhibition of growth / cell death. Kef thus shows promise as a target for the development of novel antibacterial agents.
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Theberge, Allison Lindsey. "An Investigation Correlating Bioluminescence and Metal Ruduction Utilizing Shewanella woodyi." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1555331326931868.
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Kawamoto, Jun. "Studies of cold-adaptation mechanism of a psychrotrophic bacterium, Shewanella livingstonensis Ac10." Kyoto University, 2008. http://hdl.handle.net/2433/136582.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第13493号
農博第1670号
新制||農||951(附属図書館)
学位論文||H20||N4318(農学部図書室)
UT51-2007-T869
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 江﨑 信芳, 教授 清水 昌, 教授 阪井 康能
学位規則第4条第1項該当
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SANTOS, Rogério William. "Isolamento e Caracterização de Cepas Shewanella Sp. Do Cultivo Heterotrófico de Litopenaeus Vannamei (Boone, 1931)." Universidade Federal de Pernambuco, 2014. https://repositorio.ufpe.br/handle/123456789/15667.
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CAPES
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O gênero Shewanella é um representante da classe das Gammaproteobactérias, família Shewanellaceae, compondo um grupo de bactérias gram-negativas, móveis, baciliforme, oxidase positiva, comumente encontrada em ambiente marinho e isolada do trato digestivo de animais aquáticos. Devido a suas características vem sendo amplamente testado como probiótico na carcinicultura. Estes têm sido utilizados na aquicultura para o controle biológico, aumento da taxa de conversão alimentar e sistema imune dos camarões. Este estudo teve por objetivo identificar potenciais bactérias probióticas retiradas do hepatopâncreas e estômago do camarão cultivado em sistema heterotrófico, avaliar as relações filogenéticas das cepas com o gênero Shewanella e caracteriza-las através de análisesmorfológicas, bioquímicas, produção de biofilme e antibiograma. A partir do cultivo heterotrófico de Litopenaeus vannamei, foram selecionadas as cepasIPA-S.51, IPA-S.111 e IPA-S.252para identificação através do sequenciamento parcial do gene 16S rRNA e comparados ao GenBank – NCBI e RDP - Seqmatch. As cepas foram alinhadas a 45 espécies do gênero Shewanella e avaliadas filogeneticamente utilizando os métodos Neighbor-Joining, Máxima Verossimilhança e Inferência Bayesiana. Quanto àsanálises morfológicas foram avaliadas parâmetros de acordo com a similaridade a padrões estabelecidos. Os testes bioquímicos foram realizados com o auxílio dos kits BACTRAY I, BACTRAY II e BACTRAY III (Labroclin®), totalizando 30 testes bioquímicos. A avaliação da capacidade de formação de biofilme foi realizada segundo Christensen e colaboradores. No antibiograma as cepas bacterianas foram submetidas a 13 antibióticos distintos segundo à técnica de Kirby e Bauer, com três repetições. O sequenciamento das cepas revelou alta similaridade a espécie Shewanella algae, utilizando o GenBank e o RDP-seqmath. A Inferência Bayesiana apresentou maior aporte estatístico e fidelidade dentre os métodos analisados. A Shewanella upenei apresentou alta similaridade as cepas estudadas, assim como a S. algae. As análises filogenéticas não descartam a hipótese de novas espécies para IPA-S.51, IPA-S.111 e IPAS. 252. As cepas estudadas foram sensíveis aos antibióticos Ampicilina/Subactan, Ofloxacina e Tetraciclina. A caracterização fenotípica fortalece a hipótese de especiação para as cepas testadas. Portanto, a capacidade de formação de biofilme, adicionada ao alto potencial enzimático e antagonismo a patógenos, característico do gênero Shewanella, tornam estas cepas potenciais probióticos para carcinicultura.
The genus Shewanella is one representant of Gammoproteobacteria class, family Shewanellaceae, being part of gram-negative bacteria group, mobile, bacilliform, oxidasepositive, commonly found on marine environments and isolated from the digestive tract of aquatic animals. Due to its characteristics, some tests as probiotics are being carried out in carciniculture. They are being used on aquaculture for biological control, augmentations on feed conversion rates and immune system of shrimps. This study has as objective identify potentials probiotics bacteria found in the hepatopancreas and stomach of shrimps cultivated on heterotrophic based system, evaluating the strain phylogenetic relationships with Shewanella genus and characterizing them through morphological and biochemical analysis, biofilm production and antibiogram. The strains IPA-S.51, IPA-S.111 e IPA-S.252 were selected from the heterotrophic cultivation of Litopenaeus vannamei, identified through partial 16S rRNA sequencing and compared to GenBank – NCBI and RDP - Seqmatch.The strains were aligned to 45 species of Shewanella genus and phylogenetically evaluated using Neighbor-Joining,Maximum-Likelihood estimation and Bayesian Inference.Regarding the morphological analysis parameters were evaluated according with established standard similarities. The biochemical tests were conducted with the assistance of BACTRAY I, BACTRAY II and BACTRAY III (Labroclin®) kits, totalizing 30 biochemical tests.The Biofilm capacity evaluation was made according Christensen et al. Regarding the antibiogram, the bacterial strains had undergone 13 distinct antibiotics according Kirby and Bauer, with three repetitions. The strains sequencing showed high similarity to Shewanella algae species, using GenBank and RDP-seqmath.The Bayesian inference displayed higher statistic contribution e fidelity among the other methods.The Shewanella upenei showed high similarity to the strains in study also as Shewanella algae.The phylogenetic analysis does not exclude the hypothesis of IPA-S.51, IPA-S.111 e IPA-S.252 being new species.The strains studied were sensitives to the antibiotics Ampicillin/Sulbactam, Ofloxacin, Tetracyclin. The phenotypic characterization of the strains supports the hypothesis of speciation. Thus, the capacity of biofilm formation plus the high enzymatic potential and antagonism interactions to pathogens, characteristics found in the Shewanella genus, make these strains potential probiotics to carciniculture.
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McKinzi, Adonia. "A microbially-driven Fenton reaction for oxidative dechlorination of pentachlorophenol by shewanella putrefaciens." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30637.
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Szeinbaum, Nadia Heliana. "Role of microbial manganese respiration in the anaerobic cycling of nitrogen." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53407.
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Despite the environmental significance of microbial manganese reduction, the molecular mechanism of microbial manganese respiration remains poorly understood. Soluble Mn(III) has been recently found to be a dominant soluble species in aquatic systems, yet little is known about the identity of microbial populations catalyzing Mn(III) reduction in the environment nor the molecular mechanism of Mn(III) respiration. In this research, a suite of Mn(III) reduction-deficient mutant strains were isolated, including Mn(III) reduction-deficient mutant strain Mn3-1 that also displayed the ability to reduce soluble organic-Fe(III), but not solid Fe(III) oxides, demonstrating for the first time that the reduction of soluble organic-Fe(III) and solid Fe(III) oxides proceed through electron transport pathways with at least one distinct component. This work also shows that the electron transport pathway for Mn(III) reduction in S. oneidensis shares many of the electron transport components of Fe(III) and Mn(IV) reduction pathways and that Mn(IV) reduction to Mn(II) proceeds step-wise through two one-electron transfer reactions with Mn(III) as a transient intermediate. Finally, sediment incubations were carried out to enrich for NH4+ oxidizing- Mn(III) reducing consortia. The Mn(III) reducing consortium was found to be dominated by an electrogenic Ochrobactrum sp. and a Shewanella sp. The isolated Shewanella strain is able to oxidize acetate with Mn(III) as electron acceptor, an activity never observed before in a metal-reducing member of the Shewanella genus.
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Wigginton, Nicholas Scott. "Interfacial and long-range electron transfer at the mineral-microbe interface." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27441.
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The electron transfer mechanisms of multiheme cytochromes were examined with scanning tunneling microscopy (STM). To simulate bacterial metal reduction mediated by proteins in direct contact with mineral surfaces, monolayers of purified decaheme cytochromes from the metal-reducing bacterium Shewanella oneidensis were prepared on Au(111) surfaces. Recombinant tetracysteine sequences were added to two outermembrane decaheme cytochromes (OmcA and MtrC) from S. oneidensis MR-1 to ensure chemical immobilization on Au(111). STM images of the cytochrome monolayers showed good coverage and their shapes/sizes matched that predicted by their respective molecular masses. Current-voltage (I-V) tunneling spectroscopy revealed that OmcA and MtrC exhibit characteristic tunneling spectra. Theoretical modeling of the single-molecule tunneling spectra revealed a distinct tunneling mechanism for each cytochrome: OmcA mediates tunneling current coherently whereas MtrC temporarily traps electrons via orbital-mediated tunneling. These mechanisms suggest a superexchange electron transfer mechanism for OmcA and a redox-specific (i.e. heme-mediated) electron transfer mechanism for MtrC at mineral surfaces during bacterial metal reduction.
Additionally, a novel electrochemical STM configuration was designed to measure tunneling current from multiheme cytochromes to hematite (001) surfaces in various electrolyte solutions. Current-distance (I-s) profiles on hematite (001) reveal predictable electric double layer structure that changes with ionic strength. The addition of the small tetraheme cytochrome c (STC) from S. oneidensis on insulated Au tips resulted in modified tunneling profiles that suggest STC significantly modulates the double layer. This observation is relevant to understanding metal reduction in cases where terminal metal-reducing enzymes are unable to come in direct contact with reducible mineral surfaces. Electronic coupling to the mineral surface might therefore be mediated by a localized ion swarm specific to the mineral surface.Ph. D.
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Berger, Julia. "Hydration of swelling clay and bacteria interaction : An experimental in situ reaction study." Université Louis Pasteur (Strasbourg) (1971-2008), 2008. https://publication-theses.unistra.fr/public/theses_doctorat/2008/BERGER_Julia_2008.pdf.
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Cette étude traite du comportement des smectites et de leurs interactions Shewanella putrefaciens. Les résultats expérimentaux ont été obtenu en utilisant un nouveau type de cellule réactionnelle (Warr & Hoffman, 2004) conçue afin de réaliser des mesures de diffraction des rayons X (DRX) in-situ. Des calculations avec CALCMIX (Plançon & Drits, 1999) ont été utilisées pour quantifie d'eau contenue dans les différents sites de stockage (interfoliaires, surfaces et porosité). Les expériences d'hydratation de smectites en conditions abiotiques réalisées sur des bentonites naturelles et industrielles. Le taux d'hydratation abiotiques des smectites, a été défini comme fortement dépendant du type de cation interfoliaire et de la force ionique de la. La survie des bactéries dans les smectites est attribué à un apport de nutriments, de Corg, à la capacité tampon et à la surface des argiles. En conditions de volume confiné, la présence de bactéries augmente de la porositéThis study reports on the physical-chemical behaviour of smectites and their interaction with Shewanella putrefaciens. Experimental results were obtained using a reaction-cell (“wet-cell”, Warr & Hoffman, 2004) for in situ X-ray diffraction (XRD). Calculations with CALCMIX allowed to quantify different water storage sites (interlayers, surfaces and pore spaces). The rate of abiotic smectite hydration is highly dependent on the type of interlayer cation (enhanced for Ca as opposed to Na) and the ionic strength of solution. A prolonged survival of bacteria in smectite suspensions is attributed to the supply of cationic nutrients and Corg, the buffering capacity and the surface areas. In confined volume conditions, the presence of bacteria in Na-smectite clay was seen to enhance the sample porosity. In underground waste disposal sites bacterial activity can modify both chemically and physically the properties of the smectite and have to be taken into account
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Dague, Etienne. "Physico-chimie des interfaces bactérie - solution aqueuse." Nancy 1, 2006. http://docnum.univ-lorraine.fr/public/SCD_T_2006_0226_DAGUE.pdf.
Full textAbstract:
L'interface entre les bactéries et leur milieu environnant est impliquée dans de nombreux phénomènes : adhésion, biominéralisation, reconnaissance de surface. Les propriétés physico-chimiques de ces interfaces cellulaires sont le plus souvent qualifiées à des échelles macroscopiques (test d’adhésion à une surface ou à des solvants, mesure d’angle de contact…) ne permettant pas de décrire toute la complexité de ces interfaces. Afin de quantifier ces propriétés aux différentes échelles : micrométrique et nanométrique, nous avons mis en œuvre une approche basée sur des techniques microscopiques et spectroscopiques. Quatre souches du genre Shewanella ont été choisies pour la variabilité structurale de leurs enveloppes (présence détestable ou non de polymères en surface). Nous avons pu quantifier par spectroscopie de force l'effet du pH et de la force ionique sur les enveloppes bactériennes. Cette analyse des courbes de force obtenue par AFM a permis de quantifier, in situ, le module d'Young (élasticité) et aussi la constante de raideur (en relation avec la pression de turgescence de la cellule) des bactéries. L'augmentation du pH et/ou de la force ionique induit une augmentation de la souplesse nanomécanique des bactéries. D'autre part, l'analyse électrocinétique, par le biais d'outils théoriques récemment développés, a montré des relations complexes entre la mobilité électrophorétique des quatre souches bactériennes, la charge effective des cellules et leurs propriétés hydrodynamiques, jusque là ignorées en microbiologie. Ainsi, nous avons pu démontrer que les cellules sans polymère présentent une densité de charge beaucoup plus importante avec une perméabilité faible alors que les cellules avec polymères sont peu chargées mais fortement perméables. La combinaison complémentaire de ces différentes approches constitue l'originalité de notre travail et a permis d'ores et déjà, d'interpréter les phénomènes observés aux échelles macroscopiques. Par conséquent, ces nouvelles données permettent une meilleure compréhension mécanistique de la réactivité aux bactéries, notamment de leur capacité d'adhésion. Ainsi, nous proposons une hypothèse expliquant les propriétés d'adhésion, au polystyrène, des cellules modèles de notre étude. Les cellules présentant un polymère important adhèrent moins bien que celles sans polymère en raison du caractère hydrodynamique mou de leur interface et des différences de densité de charge. Les évolutions des interfaces bactériennes avec le pH et la force ionique, démontrées dans ce travail, induisent des modifications des capacités d'adhésion renforçant cette hypothèse.