Tesis sobre el tema "Spores and Biofilms"
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PORTINHA, Inês Cunha. "Exploring the evolutionary link between biofilms and spores formation in spore-formers". Master's thesis, Instituto de Higiene e Medicina Tropical, 2015. http://hdl.handle.net/10362/19323.
A percepção instalada é a de que as bactérias são organismos unicelulares. No entanto, estes organismos são capazes de se organizarem em comunidades multicelulares complexas compostas de subpopulações de células diferenciadas. Os biofilmes são um exemplo deste tipo de organização. Os biofilmes conferem protecção contra as condições desfavoráveis encontradas no hospedeiro, ao mesmo tempo que criam nichos ricos em nutrientes facilitando a implantação da população. Nos últimos anos foi demonstrado que a persistência microbiana no trato gastrointestinal humano se deve em larga medida à formação de biofilmes. Algumas bactérias que podem ser encontradas no trato gastrointestinal humano são ainda capazes de diferenciar um tipo celular altamente resistente a insultos químicos e físicos, o esporo. Nestes casos, não é claro se são os biofilmes ou os endoesporos os principais responsáveis pela persistência destes organismos, já que ambos são resistentes aos antibióticos. Neste trabalho exploramos a ligação genética entre a formação de biofilmes e a esporulação em Bacillus subtilis. Mostramos que os endoesporos produzidos em biofilmes exibem maior resistência aos UV. Mostramos que um gene, remA, conservado em bactérias formadoras de endoesporos e essencial para a formação de biofilmes é expresso durante a esporulação. remA é expresso no pré-esporo após a divisão assimétrica e na célula mãe após o envolvimento do pré-esporo. GerE reprime a expressão de remA na célula mãe em estádios tardios de desenvolvimento. Consequentemente, encontramos componentes da matriz do biofilme no manto de endoesporos maduros. Algumas das proteínas estruturais que conferem integridade à matriz do biofilme, como TasA, poderão servir como base para a montagem das camadas superficiais do esporo.
Iapichino, Martina. "Motilité individuelle et collective chez les systèmes microbiens : biofilms bactériens et dispersion de spores fongiques". Thesis, Université Côte d'Azur (ComUE), 2019. http://www.theses.fr/2019AZUR4051.
The aim of this thesis is to develop experiments to understand the physics of motility in two microbial systems, living in the realm of low Reynolds number, i.e. when viscous forces dominate over inertial forces. The first part of the thesis discusses the growth of bacterial biofilms over a solid surface. Bacterial biofilms are communities of cells closely packed together inside a polymeric matrix. From the physical viewpoint, these colonies behave as gels and the polymeric matrix creates osmotic fluxes that enable biofilms to grow and move on a surface as a community. Here I develop an experiment to explore biofilm collective motility in contact with external gradients of osmotic pressure. To produce stable osmotic gradients in agar gels, I develop a custom-made setup through millifluidics. Biofilms respond to the external gradient by developing an asymmetric shape, consistent with the expectations. The second part of the thesis discusses the spore discharge mechanism in the fungal phylum Basidiomycetes. In these species, a drop coalesces with the spore, which results in spore discharge at enormous accelerations. This surface tension catapult reaches its maximum efficiency when the size of the drop is comparable to that of the spore. I study morphologies of several gilled mushrooms, where spores are packaged at the surface of complex shaped gills. I find that for those species, drop size must be precisely controlled. This poses the question of how mushrooms may regulate a process that occurs extracellularly, despite fluctuating physical conditions
Le, Toquin Esther. "Mode d'action biocide de nouveaux procédés de décontamination sur deux formes de résistances bactériennes". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR103/document.
Several decontamination technologies exist, however bacterial spores and biofilms remain a concern in a lot of fields, like hospital, alimentary and military. A new foam containing a biocide (sodium hypochlorite or hydrogen peroxide) and a stabilizing agent (Xanthan) has been studied to answer this problematic. This foam can be used in different ways on the field following contaminations: grounds’ spraying, walls’ covering and spraying, full pieces’ filling (walls and ground). The goal of this thesis is to evaluate the biocide efficiency of these foams on spores and biofilms. We optimized experimental protocols in order to study mechanisms of foams’ action on spores and biofilms based on theirs future applications (horizontal, vertical and filling) and depending on different environmental factors which may impact foam decontamination efficiencies (materials, temperatures, soil, …). This thesis work enabled to highlight the Xanthan foam containing 5% NaOCl from the one including 12% H2O2 in military sector. This foam allows a rapid decontamination, about 7 logs of spores in 30 minutes, for each of the three ways of use at 20°C. Moreover, the destruction of biofilms containing 107 logs of bacteria/cm² was achieved in 1 hour on a horizontal support by filling. This NaOCl foam is ready to be used for industrials
Al, Saabi Alexandre-Ahmad. "Mousses en écoulement pour le nettoyage d’équipements fermés contaminés par des spores de Bacillus cereus ou des biofilms de Pseudomonas fluorescens". Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R015.
Contaminants such as spores/biofilms are problematic in many food industry sectors. Indeed even after hygiene procedures, biofilms/spores could be found on every surface that is in direct contact or not with food (Bénézech & Faille, 2018). Risks associated with microorganisms can be controlled either by limiting the number of adherent cells or by facilitating the removal of adherent bacteria. Even though Cleaning in Place (CIP) is widely used and it is a common cleaning practice in food industries; however, it remains at some level a high- water consumption procedure. In addition, some studies, presented some bacterial species that still survived even after CIP and maybe a probable source of product contamination. On the other hand, a double phase fluid such as foam can impose the same wall shear stress with less water being consumed. Foam with its properties such as shearing can be key a parameter for a mechanical cleaning of closed systems such as pipes with a lower consumption of water.In this study we investigated the effect of flowing foam in pipes and compared its efficiency with standard CIP like conditions on the detachment of spores and biofilms. The first approach was working with different foam flow regimes (1D, 2D, 3D while increasing the velocity from 2 to 6 cm s-1) having different foam qualities (amount of air: 50%, 60%, 70%) on different species of microorganisms where fouling was performed either by using spores of B. amyloliquefaciens 98/7 or B. cereus 98/4 that shows a difference by their hydrophobic/hydrophilic character. As for P. fluorescens pf1 it was used as a good biofilm former (24 hrs. biofilm) widely encountered in the food industry. Fouling was performed either vertically or horizontally inducing biofilms with different structures. Results from foam cleaning were compared with CIP like conditions results (the same mean mechanical action, and the same concentration of surfactant). The second approach was subjecting foam flow to different singularities (sudden expansion gradual reduction – bends) while working with one foam flow regime (1D 50%) and one species (B. amyloliquefaciens 98/7 spores) to highlight any changes in the foam flow cleaning efficiency. The third approach was working also with one species (B. amyloliquefaciens 98/7) considered as a good “microbial tool” producing foam from the use of different surfactants (SDS, Capstone® FS 30, Ammonyx® LO) that differs by their chemical properties ( nonionic, anionic and zwitterion) thus producing different foams having different physical properties in terms of bubbles size , number and repartition, and flow pattern. Comparing to previous related works on foam flow characterization, it was possible to highlight the potential role on the cleaning efficiency of the Wall Shear Stress variations in parallel to the liquid film thickness variation at the wall with the bubbles' passage. In addition, according to previous work, the possible capillary forces exerted under the lowest flow rates and considering the hydrophilic/hydrophobic nature of the spores, in addition to biofilm structure would explain at least partly the surprising efficiency in the spores' removal by foam
Al, Saabi Alexandre-Ahmad. "Mousses en écoulement pour le nettoyage d’équipements fermés contaminés par des spores de Bacillus cereus ou des biofilms de Pseudomonas fluorescens". Electronic Thesis or Diss., Université de Lille (2018-2021), 2020. http://www.theses.fr/2020LILUR015.
Contaminants such as spores/biofilms are problematic in many food industry sectors. Indeed even after hygiene procedures, biofilms/spores could be found on every surface that is in direct contact or not with food (Bénézech & Faille, 2018). Risks associated with microorganisms can be controlled either by limiting the number of adherent cells or by facilitating the removal of adherent bacteria. Even though Cleaning in Place (CIP) is widely used and it is a common cleaning practice in food industries; however, it remains at some level a high- water consumption procedure. In addition, some studies, presented some bacterial species that still survived even after CIP and maybe a probable source of product contamination. On the other hand, a double phase fluid such as foam can impose the same wall shear stress with less water being consumed. Foam with its properties such as shearing can be key a parameter for a mechanical cleaning of closed systems such as pipes with a lower consumption of water.In this study we investigated the effect of flowing foam in pipes and compared its efficiency with standard CIP like conditions on the detachment of spores and biofilms. The first approach was working with different foam flow regimes (1D, 2D, 3D while increasing the velocity from 2 to 6 cm s-1) having different foam qualities (amount of air: 50%, 60%, 70%) on different species of microorganisms where fouling was performed either by using spores of B. amyloliquefaciens 98/7 or B. cereus 98/4 that shows a difference by their hydrophobic/hydrophilic character. As for P. fluorescens pf1 it was used as a good biofilm former (24 hrs. biofilm) widely encountered in the food industry. Fouling was performed either vertically or horizontally inducing biofilms with different structures. Results from foam cleaning were compared with CIP like conditions results (the same mean mechanical action, and the same concentration of surfactant). The second approach was subjecting foam flow to different singularities (sudden expansion gradual reduction – bends) while working with one foam flow regime (1D 50%) and one species (B. amyloliquefaciens 98/7 spores) to highlight any changes in the foam flow cleaning efficiency. The third approach was working also with one species (B. amyloliquefaciens 98/7) considered as a good “microbial tool” producing foam from the use of different surfactants (SDS, Capstone® FS 30, Ammonyx® LO) that differs by their chemical properties ( nonionic, anionic and zwitterion) thus producing different foams having different physical properties in terms of bubbles size , number and repartition, and flow pattern. Comparing to previous related works on foam flow characterization, it was possible to highlight the potential role on the cleaning efficiency of the Wall Shear Stress variations in parallel to the liquid film thickness variation at the wall with the bubbles' passage. In addition, according to previous work, the possible capillary forces exerted under the lowest flow rates and considering the hydrophilic/hydrophobic nature of the spores, in addition to biofilm structure would explain at least partly the surprising efficiency in the spores' removal by foam
Dallagi, Heni. "Numerical and experimental investigations of the rheological behavior of foam flow : application to the cleaning of surfaces contaminated by microorganisms in the food industries". Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR003.
In this research, experimental and numerical characterization of the rheological behavior of an aqueous foam flowing inside a horizontal pipe with and without singularities (presence of half-sudden expansion, and a fence) were investigated. Different conditions of foam flow were studied by varying the foam qualities (from 55% to 85%), and three Reynolds numbers (32, 65, and 97). Measurements of the pressure measurements, and at the wall the local velocity repartition and the thickness of the liquid films using respectively pressure sensors, Particle Image Velocimetry, and a conductimetry technique shown a reorganization of the foam downstream the geometry change, with a thicker liquid film at the duct bottom, larger bubble sizes at the top, as well as a larger foam void fraction increased from the bottom to the top part of the duct section. In addition, foam would present a visco-elastic character comparable to a non-Newtonian monophasic liquid. Computational Fluid Dynamics simulations were undertaken to predict this rheological behavior of the foam, the two models Herschel-Bulkley and Bingham were tested taken into account the presence of an underlying liquid film at the bottom of the channel . Comparison between experimental and numerical results showed that regardless of the foam quality, Herschel-Bulkley model could accurately describe the rheological behaviour of the aqueous foam under the different flow conditions analysed.The second target was to investigate the ability of a wet foam flow (quality of 50%) to clean stainless-steel surfaces contaminated by microorganisms. For this purpose, two different contamination patterns were studied, droplets containing Bacillus subtilis spores (either hydrophilic Bs PY79 or hydrophobic Bs PY79 spsA), and biofilms produced by three bacteria strains encountered in food industry production plants (Escherichia coli SS2, Bacillus cereus 98/4, and Pseudomonas fluorescens Pf1). Different flow conditions were performed by varying the wall shear stresses (2.2 - 13.2 Pa), and bubble sizes (0.18-0.34 mm) in a straight duct with no geometrical changes, in order to identify the mechanisms of contamination release and thus better control and optimize the foam cleaning process. Results show that compared to conventional cleaning-in-place, foam flow effectively removed Bs spores as well as Bc-98/4, Ec-SS2, and Pf1 biofilms. Moreover, the combination of high shear stress at the wall and small bubble sizes (<0.2 mm) showed promise for improving the cleaning efficiency of spores. On the other hand, a clear improvement of the biofilm removal was observed when increasing the mean wall shear stress. The characterization of the foam and the interface phenomenons (using polarography, conductimetry, and bubble size analysis methods) indicated that mechanisms such as fluctuation in local wall shear stresses, or in the liquid film thickness between the bubbles and the steel wall induced by bubble passage, foam imbibition, and sweeping of the contamination within the liquid film could participate largely to the removal mechanisms. Finally, the life cycle assessment study demonstrated that foam flow cleaning could be a suitable technique to reduce water and energy consumption (7 and 8 times less, respectively) presenting less environmental impacts than CIP processes, with about 70%. Lastly, foam flow cleaning can be an alternative method, which can improve efficiency and reduce environmental impact. Additional activities conducted during the PhD period related to hygienic design are presented highlighting the role of the contaminants (spores and biofilms), the material (other than stainless steel) and the geometry (ducts or more complex design) in hygiene monitoring
Ribeiro, Maria Cecília Enes. "Adesão e formação de biofilme por Bacillus cereus em aço inoxidável". [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/255191.
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-30T23:01:21Z (GMT). No. of bitstreams: 1 Ribeiro_MariaCeciliaEnes_D.pdf: 17038739 bytes, checksum: 54c8350faac4b14e773283e6e871aa78 (MD5) Previous issue date: 2015
Resumo: O objetivo geral deste trabalho foi avaliar o efeito de diferentes matrizes na adesão e formação de biofilme em aço inoxidável por Bacillus cereus, bem como avaliar a eficiência dos procedimentos de higienização no controle de biofilmes de esporos desse micro-organismo. Nas duas primeiras etapas, avaliou-se a capacidade de adesão e formação de biofilme por B. cereus em aço inoxidável, com e sem prévio condicionamento da superfície, utilizando-se água, leite UHT desnatado e integral como matrizes e quatro diferentes tipos de inóculos, pool de células vegetativas de B. cereus isolados da indústria láctea, pool de esporos de B. cereus isolados da indústria láctea, células vegetativas da cepa de B. cereus ATCC 14579 e esporos da cepa de B. cereus ATCC 14579. Na terceira etapa do trabalho avaliou-se a influência da matriz condicionante (água e leite UHT integral), do meio de inoculação do pool de esporos de B. cereus (água e leite UHT integral) e do tempo de exposição (5 min (0,08h), 10, 24, 48 e 72 horas) sobre a adesão e formação de biofilme por B. cereus em aço inoxidável. Na quarta etapa, avaliou-se a eficiência de nove procedimentos de higienização na remoção dos biofilmes formados pelo pool de esporos de B. cereus em aço inoxidável. Todos os experimentos foram repetidos três vezes e os dados estatisticamente avaliados. A hidrofobicidade e o potencial zeta das superfícies dos esporos também foram avaliados. Os resultados das duas primeiras etapas indicaram que o pool de esporos de B. cereus isolados de indústria láctea apresentou a maior capacidade de adesão e formação de biofilme em aço inoxidável quando comparado aos outros tipos de inóculos, em todas as condições avaliadas. O maior grau de adesão de esporos de B. cereus (4,93 log UFC/cm2) foi observado ao se utilizar leite integral como matriz condicionante do aço inoxidável. Entretanto, comparando-se todas as matrizes, a menor adesão (3,01 log UFC/cm2) foi observada quando o pool de esporos de B cereus foi veiculado no leite integral sem prévio condicionamento da superfície. Na terceira etapa do trabalho observou-se que a adesão e formação de biofilme pelo pool de esporos de B. cereus foi maior quando inoculados em água, independente das matrizes de condicionamento. A adesão de B. cereus aumentou 1,02 e 0,3 log UFC/cm2 ao longo do tempo de exposição, quando o pool de esporos de B. cereus foi inoculado em água e leite integral, respectivamente. O biofilme de esporos veiculados na água apresentou maior resistência aos procedimentos de higienização. A sanitização com hipoclorito de sódio foi mais eficiente na remoção dos biofilmes quando comparada ao ácido peracético. O pool de esporos de B. cereus isolados da indústria láctea foi altamente hidrofóbico e apresentou carga negativa em uma ampla faixa de pH, com ponto isoelétrico de aproximadamente 3,0. Os esporos de B. cereus isolados da indústria láctea apresentaram maior capacidade de adesão ao aço inoxidável quando comparados aos outros inóculos avaliados, o que pode estar relacionado à alta hidrofobicidade e a baixa carga de superfície dos esporos
Abstract: The aim of this study was to evaluate the effect of different matrices on the adhesion and biofilm formation by Bacillus cereus on stainless steel, and to evaluate the effectiveness of sanitation procedures for controlling biofilm from spores of this microorganism. The first two parts were carried out in order to evaluate the adhesion and biofilm formation by B. cereus on stainless steel, with and without previous conditioning of the surface, using water, skim and whole UHT milk as matrices and four different types of inocula: a pool of B. cereus vegetative cells isolated from dairy industry, a pool of B. cereus spores isolated from dairy industry, vegetative cells of B. cereus ATCC 14579, and spores of B. cereus ATCC 14579. The third part of the study evaluated the effect of the conditioning matrix (water and whole UHT milk), the inoculation medium of pool of B. cereus spores (water and whole UHT milk) and exposure time (5 min (0.08h), 10, 24, 48 and 72 hours) on the adhesion and biofilm formation by B. cereus on stainless steel. In the fourth part, the effect of nine sanitation procedures on the removal of B. cereus spores biofilm was evaluated. All experiments were repeated three times and data were statistically evaluated. Hydrophobicity and zeta potential from spore¿s surface were also evaluated. Regarding the results to the first and second parts, the pool of B. cereus spores isolated from dairy industry had the highest ability of adhesion on stainless steel when compared to the other inocula, for all tested conditions. After stainless steel surface conditioning with whole milk, B. cereus spores showed the highest adhesion (4.93 log CFU/cm2). However, lower adhesion (3.01 log CFU/cm2) was observed when B. cereus spores were delivered in whole milk as compared to the other matrices, without previous conditioning of the surface. The results of the third part indicated that the adhesion and biofilm formation by the pool of B. cereus spores was higher when they were inoculated in water, regardless of the conditioning matrix. B. cereus spores adhesion increased by 1.02 and 0.3 log CFU/cm2 over exposure time, when the pool of B. cereus spores was inoculated into water and whole milk, respectively. Biofilm of B. cereus spores inoculated in water showed the highest resistance against all tested sanitation procedures. Sodium hypochlorite was the most effective sanitizer for removing all biofilms when compared to the peracetic acid. The pool of B. cereus spores isolated from dairy industry was highly hydrophobic and showed a negative charge at a wide pH range, with an isoelectric point of about 3.0. B. cereus spores isolated from dairy industry showed the highest ability to adhere on stainless steel when compared to the other inocula, which is possibly related to its higher hydrophobicity and lower spore surface charge
Doutorado
Tecnologia de Alimentos
Doutora em Tecnologia de Alimentos
Shane, William T. "Persistence of Spore Forming Bacteria on Drinking Water Biofilm and Evaluation of Decontamination Methods". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1205164893.
Packard, Benjamin H. "Retention and Removal of Bacterial Endospores from Common Drinking Water Distribution System Pipe Materials". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1277132818.
Gorinati, Camilla. "Caratterizzazione funzionale di sorgenti plasma di non equilibrio a pressione atmosferica per l’eradicazione di biofilm batterici e l’inattivazione di spore". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Fuchs, Felix Matthias. "Bacillus subtilis biofilm formation under extreme terrestrial and simulated extraterrestrial conditions". Doctoral thesis, 2020. http://hdl.handle.net/21.11130/00-1735-0000-0005-13A9-7.
Gonçalves, Bruno Alexandre Amaral. "Studies on the relationship between assembly of the spore coat and the biofilm". Master's thesis, 2020. http://hdl.handle.net/10451/48586.
In the model organism Bacillus subtilis, the surface of the spore consists of a protein coat that affords protection against noxious chemicals and lytic enzymes and modulates spore germination and binding to cells and abiotic surfaces. The coat, formed by over 80 proteins, is divided into an inner layer, an outer layer and a crust. The coat proteins are synthesized in the mother cell and are recruited to the surface of the developing spores through specific protein-protein interactions and also according to successive waves of gene expression. SafA is a morphogenetic protein responsible for the assembly of the inner coat layer. SafA exists in three forms, the full-length protein, SafAFL, SafAC30 which corresponds to the C-terminal moiety of the protein, and SafAN21, corresponding to the N-terminal moiety of the protein. The C30 region is responsible for recruiting the inner coat proteins, whereas the N-terminal region carries the signals for localization at the spore surface. Among the proteins that SafA recruits to the inner coat is a transglutaminase, called Tgl, in a process termed substrate-driven localization. Assembly of SafA is auto-regulatory in that once assembled, Tgl introduces ε-(γ glutamyl)lysil bonds into SafA. SafAC30 forms an oblong hexamer, (SafAC30)6 and this species is cross linked in vitro by Tgl. Strikingly, the activity of Tgl decreased with increasing SafAC30 concentration, suggesting both that Tgl cross-linked itself to SafAC30 and a mechanism for controlling the activity of the enzyme in vivo. Here we overproduced and purified SafAFL and SafAN21 and tested for cross-linking by purified Tgl. Although Tgl proved to be much less efficient in cross-linking SafAN21 than SafAFL or SafAC30, its activity was inversely proportional to the concentration of all three substrates. Thus, in vitro, all three forms of SafA have the potential of controlling the activity of Tgl in a concentration-dependent manner. That SafAN21 is a poor substrate for Tgl, in spite of the fact that it contains several glutamine and lysine residues, suggests that this region of SafA is not involved in cross-linking to itself or to Tgl in vivo and raises the possibility that it may be involved in cross-linking to another protein or directly to the cortex peptidoglycan. Moreover, we found that formation of (SafAC30)6 involves disulfide bonds and that Tgl exerts a “spotwelding” activity on this species, i.e., not all the monomers in (SafAC30)6 are cross-linked by Tgl. Two lysine residues in SafAC30, K177 and K318 are important for this activity but K318 makes a more important contribution. Since K318 is close to two of the four cysteine residues in SafAC30, C323 and C325, and also in the close vicinity of several glutamine residues, a model is proposed in which disulfide bond formation at this position nucleates further cross-linking of (SafAC30)6 by Tgl. Veg, an 86 amino acid protein, was known to influence biofilm formation and spore germination. The veg gene is downstream of yabG, a gene that is part of a genomic signature for sporulation. yabG codes for a cysteine protease required for processing of the Tgl substrates prior to their cross-linking by Tgl. YabG also functions in the assembly of the spore surface layers in the human pathogen Clostridioides difficile. Here, we have shown that the overexpression of veg during the late stages of sporulation in B. subtilis impairs assembly of the abundant CotB and CotG, the latter a critical determinant of the structural organization of the outer coat. The assembly of other proteins, such as the peptidoglycan hydrolase YdhD and of a putative L-cysteine binding protein was also affected. Veg bears a Sm-like motif characteristic of proteins that regulate mRNA stability and translation in all domains of life. Molecular modelling studies suggest that, like the Sm proteins, Veg forms an heptamer with a central channel and a positively charged surface that may mediate interactions with single-stranded nuclei acids. Veg may thus define a novel level of control in spore coat assembly, influencing mRNA stability and/or translation and we propose that it functions in the same way in biofilm development. We overproduced and purified the C. difficile Veg protein, an 11 kDa protein with significant similarity to B. subtilis Veg. The structural and biochemical characterization of Veg will provide important insights into its function and its suspected functional relationship to YabG.
Putri, TP. "Understanding thermophilic spore-forming bacteria in milk powders". Thesis, 2017. https://eprints.utas.edu.au/27361/1/Putri_whole_thesis.pdf.
Balasubramanian, Srikkanth. "Novel anti-infectives against pathogenic bacteria". Doctoral thesis, 2018. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-163882.
Meeresschwamm-assoziierte Actinomyceten stellen ein Reservoir für verschiedene natürliche Produkte mit neuartigen biologischen Aktivitäten dar. Ihr antibiotisches Potenzial gegenüber einer Reihe von Gram-negativen und -positiven Bakterien ist bereits intensiv erforscht worden. Wenig ist allerdings über ihre antiinfektive und antivirulente Wirksamkeit gegenüber menschlichen Pathogenen bekannt. Ziel dieser Doktorarbeit war es, die antiinfektiven Fähigkeiten (anti-Shiga-Toxin und anti-Biofilm) der aus Schwämmen isolierten Actinobakterien zu untersuchen. Hierfür wurden bioaktive Metabolite der Actinobakterien identifiziert und isoliert und abschließend wurde ihr Wirkmechanismus mit Hilfe einer Transkriptomanalyse charakterisiert. Diese Arbeit ist in drei Studien gegliedert, welche alle zum Ziel hatten die antiinfektive Wirksamkeit von aus Actinomyceten gewonnenen Extrakten und Komponente(n), welche möglicherweise als zukünftige Therapeutika dienen könnten, zu untersuchen. Die erste Studie befasst sich mit den anti-Shiga-Toxin Effekten der Meeresschwamm- assoziierten Actinomyceten. Durchfallinfektionen stellen in vielen Entwicklungsländern aber auch in Industrieländern eine große Gefahr dar. Durchfallerkrankungen die durch enterohämorrhagische Escherichia coli (EHEC) hervorgerufen werden, können sich zu lebensbedrohlichen Komplikationen wie Gastroenteritis oder dem hämolytisch urenischen Syndrom (HUS) weiterentwickeln. Das von den EHEC Stämmen produzierte Shiga-Toxin (Stx) stellt hierbei den Haupt Virulenz Faktor dar, welcher die eukaryotische Proteinsynthese menschlicher Zellen negativ beeinflusst, was wiederum den Zelltod durch Apoptose zur Folge hat. Die Behandlung der EHEC-Patienten mit Antibiotika wird nicht empfohlen, da dies zu einem Anstieg von freigesetztem Stx der zersetzen Bakterien führen könnte, wodurch das Risiko für die Entwicklung des HUS ansteigt. Aus diesem Grund werden effektive Medikamente dringen benötigt, welche die Stx Produktion blockieren ohne das Wachstum der Bakterien zu beeinflussen. In dieser Studie wurden 194 Extrakte und einige isolierte Komponenten von aus Schwämmen gewonnenen Actinomyceten auf ihren negativen Einfluss auf die Stx Produktion des EHEC Stammes EDL933 mit der Hilfe des Ridascreen® Verotoxin ELISA Kits untersucht. Es konnte gezeigt werden, dass die Zugabe der Extrakte keinen signifikanten Einfluss auf die Stx Produktion hatte. Strepthonium A auf der anderen Seite, welches aus Streptomyces sp. SBT345 isoliert wurde (vom mediterranen Schwamm Agelas oroides) konnte die Stx Produktion von EDL933 bei einer Konzentration von 80 µM reduzieren ohne das Wachstum des EHEC Stammes zu beeinflussen. Die Struktur von Strepthonium A wurde mittels spektroskopischer Analyse (1D- und 2D-NMR), sowie mittels ESI-HRMS und ESI-HRMS2 Experimenten entschlüsselt. Basierend auf diesen Ergebnissen könnte Strepthonium A eine mögliche Alternative oder Zusatz in der Behandlung einer EHEC Infektion darstellen. In der zweiten Studie wurde der Einfluss der Meeresschwamm-assoziierten Actinomyceten auf die Biofilmbildung von Staphylokokken bewertet. Medizinische Produkte wie Kontakt Linsen, metallische Implantate, Katheter, Herzschrittmacher, usw. stellen optimale ökologische Nischen für die Ausbildung von bakteriellen Biofilmen dar, wodurch Infektionen im Menschen hervorgerufen werden können. Bakterien in einem Biofilm sind deutlich toleranter gegenüber der Immunantwort ihres Wirtes sowie gegenüber konventionellen Antibiotika und sind daher schwer zu bekämpfen. In dieser Studie wurde das anti-Biofilm Potential eines organischen Extrakts der flüssigen Fermentation von Streptomyces sp. SBT343 (vom mediterranen Schwamm Petrosia ficiformis) ermittelt. In vitro Ergebnisse zeigten, dass das organische Extrakt anti-Biofilm (gegenüber Staphylococci) Fähigkeiten besitzt und nicht toxisch für Maus Makrophagen (J774.1), Fibroblasten (NIH/3T3) und humane korneale Epithelzellen ist. Zudem konnte gezeigt werden, dass das SBT343 Extrakt die Ausbildung eines Biofilms von Staphylokokken auf den Oberflächen von Polystyrol, Glass und Kontaktlinsen unterbinden konnte ohne das bakterielle Wachstum zu beeinflussen. Die hochauflösende Fouriertransformation-Massenspektrometrie (HR-MS) Analyse konnte die Komplexität sowie die chemische Vielfalt an Komponenten im Extrakt aufzeigen. Eine vorläufige, physio-chemische Charakterisierung deutet darauf hin, dass die aktive Komponente im Extrakt hitzestabil und nicht proteinartiger Natur ist. Abschließend konnte durch Fraktionierungsexperimente gezeigt werden, dass die biologische Aktivität auf synergistischen Effekten mehrerer Komponenten im Extrakt beruht. In einer dritten Studie wurden 50 organische Extrakte, welche aus fester und flüssiger Fermentierung von 25 verschiedenen aus Meeresschwämmen isolierten Actinomyceten gewonnen wurden, auf anti-Biofilm-Aktivität untersucht. Hierbei wurde die anti-Biofilm Aktivität des organischen Extrakts der Festkultur von Streptomyces sp. SBT348 (vom mediterranen Schwamm Petrosia ficiformis) identifiziert. Eine Bioassay gestützte Fraktionierung führte zu der Identifikation der aktiven Fraktion Fr 7 im SBT348 Extrakt. Durch weitere Aufreinigung des Extrakts mit einer semipräparativen HPLC, konnten die bioaktiven Sub-Fraktionen SKC1, SKC2, SKC3, SKC4 und SKC5 isoliert werden. Die Sub- Fraktion SKC3 hatte den stärksten anti-Biofilm Effekt und bestand aus einer reinen Verbindung mit BIC90 und MIC Werten von 3,95 µg/ml und 31,25 µg/ml gegen S. epidermidis RP62A. SKC3 zeigte weder erkennbare Toxizität gegenüber Zelllinien in vitro noch gegenüber den Larven der großen Wachsmotte Galleria melonella in vivo. SKC3 war Hitze- und Enzym-resistent, was auf eine nicht proteinartige Natur hindeutet. Eine HR-MS Analyse ergab, dass die Masse von SKC3 1258,3 Da beträgt. Die Strukturanalyse von SKC3 durch 1D und 2D-NMR ist zurzeit in Bearbeitung. Um weiteres Verständnis über den anti-Biofilm Wirkmechanismus von SKC3 auf S. epidermidis RP62A zu erlangen, wurde eine RNA Sequenzierungsanalyse durchgeführt. Die Transkriptomanalyse zeigte, dass SKC3 von RP62A nach einer 20-minütigen Inkubationszeit erkannt wird und dass SKC3 den zentralen Metabolismus des Staphylokokken Stammes nach 3 h negativ beeinflusst. Zusammengenommen deuten die Ergebnisse darauf hin, dass SKC3 als Leitstruktur für die Entwicklung neuer anti- Staphylokokken Medikamente dienen könnte. Zusammenfassend heben die Ergebnisse dieser Arbeit die antiinfektiven Eigenschaften der Meeresschwamm-assoziierte Actinomyceten hervor und bieten eine Möglichkeit für die Nutzung dieser in Wirkstoffentwicklungsprogrammen
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