Dissertationen: „Metal tolerant“

1

Mullins, M. „Subcellular localization of metals in metal tolerant higher plants“. Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384378.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

2

Lees, Fiona M. „Studies on metal-tolerant estuarine algae“. Thesis, Heriot-Watt University, 1985. http://hdl.handle.net/10399/1620.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

3

Duggan, Sam B. „Complex metal mixture reduces apparent protein carbonylation in a tolerant aquatic macroinvertebrate, Arctopsyche grandis“. Thesis, Colorado State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=1606539.

Der volle Inhalt der Quelle

Annotation:

Mining is widespread and an economically important industry. Unfortunately, acid mine drainage (AMD) can pollute ecosystems with a cocktail of contaminants too complex for accurately forecasting its health consequences. However, through quantification of fundamental toxic events, the effects of complex mixtures can be observed. This project explored two potentially insightful and convenient endpoints. First, oxygen consumption (MO₂), a well-established and sensitive indicator of respiratory impairment was utilized. Second, protein carbonyl content (PCC), an experimental ecological biomarker widely lauded in biomedical circles as a highly conserved indicator of health status was assessed for its utility in a metal tolerant aquatic macroinvertebrate, Arctopsyche grandis. A. grandis were exposed to eight environmentally relevant target concentrations (in duplicate) of AMD for eight days at a temperature controlled greenhouse containing artificial flow-through streams. As expected, MO₂ was inversely related to treatment concentration (R²=0.35, p=0.015). Protein carbonyl content, however, diverged from predictions. Protein carbonyl content analysis detected significantly more oxidative protein injury in control treatments than in metal-rich AMD treatments (p<0.001). Moreover, there was not a significant difference in PCC between different AMD concentrations. Protein carbonyl content’s departure from anticipated results likely is the consequence of dynamic interactions between direct and indirect effects at the chemical, biochemical, physiologic and behavioral levels. The results of this project illustrate flaws of utilizing a single biochemical marker to observe effects of a toxic mixture. Rather, a broad suite of biomarkers should be assayed to determine sublethal toxicity. These results also illustrates how multiple stressors can yield unanticipated outcomes.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

4

Yadav, Krishna Kant. „Studies on the molecular physiology of bio-film formation in metal tolerant bacteria- Acinetobacter junii BB1A (Acc.no.LMG 22734)“. Thesis, University of North Bengal, 2013. http://ir.nbu.ac.in/hdl.handle.net/123456789/1515.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

5

Gokul, Arun. „Impact of vanadium stress on physiological and biochemical characteristics in heavy metal susceptible and tolerant Brassicaceae“. University of the Western Cape, 2013. http://hdl.handle.net/11394/3582.

Der volle Inhalt der Quelle

Annotation:

There is an influx in heavy metals into soils and ground water due to activities such as increased mineral mining, improper watering and the use of heavy metal contaminated fertilizers. These heavy metals are able to increase the ROS species within plants which may result in plant metabolism deterioration and tissue damage. Heavy metals may also directly damage plants by rendering important enzymes non-functional through binding in metal binding sites of enzymes. The heavy metal focused on in this study was vanadium due to South Africa being one of the primary produces of this metal. Two related Brassica napus L cultivars namely Agamax and Garnet which are economically and environmentally important to South Africa were exposed to vanadium. Physiological experiments such as cell death, chlorophyll and biomass determination were conducted to understand how these cultivars were affected by vanadium toxicity. A low cost, sensitive and robust vanadium assay was developed to estimate the amount of vanadium in samples such as water, soils and plant material. The oxidative state as well as the antioxidant profile of the two cultivars were also observed under vanadium stress. A chlorophyll assay which was conducted on the two cultivars xiv exposed to vanadium showed a marked decrease in chlorophyll A in the suspected sensitive cultivar which was Garnet. However, the suspected tolerant cultivar Agamax fared better and the decrease in chlorophyll A was much less. A similar trend was observed for the two cultivars when the cell death assay was conducted. The vanadium assay showed that Garnet had higher concentrations of vanadium within its leaves and lower concentrations in its roots when compared to Agamax. This observation displayed that Agamax had inherent mechanisms which it used to localize vanadium in its roots and which assisted in its tolerance to the vanadium stress. The oxidative state was determined by doing assays for the specific reactive oxygen species namely hydrogen peroxide and superoxide. It was observed that vanadium treated Garnet leaves had higher reactive oxygen species (ROS) production when compared to the Agamax treated leaves. In-gel native PAGE activity gels were conducted to determine the antioxidant profile for the two cultivars which were exposed to vanadium. The antioxidant enzymes which were under investigation were ascorbate peroxide (APX), superoxide dismutase (SOD) and glutathione-dependent peroxidases (GPX-like) as these enzymes are known to be responsible for controlling the ROS produced in the plants. The GPX-like profile consisted of three isoforms. No isoforms were inhibited by vanadium treatments but one isoform had increased activity in both the Garnet and Agamax treated samples. The SOD profile for Garnet consisted of six isoforms xv and Agamax had seven isoforms. One isoform which was visualized in both Agamax as well as Garnet was inhibited by vanadium treatments. Agamax also had two isoforms which were up-regulated however the corresponding isoforms in Garnet showed no change. The Ascorbate peroxidase profile consisted of seven isoforms for both Garnet and Agamax. No isoforms were inhibited by vanadium treatment. Three isoforms were up-regulated in Garnet and Agamax under vanadium treatments. Here, it is illustrated that Garnet lacked certain mechanisms found in Agamax (and thus experienced more cell death, yield and chlorophyll loss) and performed worst under high vanadium concentrations. Although Garnet increased the activity of some of its antioxidant isoforms in response to increasing ROS levels it was not adequate to maintain a normal oxidative homeostasis. This disruption in oxidative homeostasis lead to plant damage. Agamax was observed to produce less ROS than Garnet and was able to control the ROS produced more effectively than Garnet and thus less damage was observed in Agamax.
Magister Scientiae - MSc

APA, Harvard, Vancouver, ISO und andere Zitierweisen

6

Choudhary, Aarti. „A process variation tolerant self compensation sense amplifier design“. Connect to this title, 2008. http://scholarworks.umass.edu/theses/166/.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

7

Mahlatsi, Tladi Abram. „Characterization of heavy metal tolerant bacterial plasmids isolated from a platinum mine tailings dam / by Tladi Abram Mahlatsi“. Thesis, North-West University, 2012. http://hdl.handle.net/10394/9780.

Der volle Inhalt der Quelle

Annotation:

The development of metal-tolerance and antibiotic resistance in bacteria may be caused by metals polluting a particular environment. During mining and mineral processing activities, large quantities of metals are deposited into the soil. These high concentrations of metals are evolutionary pressures selecting for microorganisms tolerant to these metals. Metaltolerance maybe conferred to these organisms by mobile genetic elements such as plasmids. This study describes the characteristics of plasmids isolated from various bacteria that displayed an ability to withstand high metal concentrations. The isolated plasmids were individually transformed into Escherichia coli JM109. Transformants were then evaluated for metal-tolerant capabilities using a microdilution approach. Plasmids were then isolated from the transformants and the concentration of the plasmid DNA ranged between 11.75 – 118.06 ng/μl. These plasmids were of the same size as the original ones. This demonstrated that successful transformations with plasmid DNA were conducted. In order to determine the compatibility group, plasmids were subjected to PCR amplification using IncQ, IncP-9 and IncW specific primers. Only the IncW provided positive results. To demonstrate that the plasmids were free of genomic DNA, a 16S rDNA PCR test was included. The plasmids that were positive for IncW PCRs were all negative for the rDNA PCRs. Plasmids were stably inherited and at least three, isolated from three different Gram positive species, belonged to the Inc W group of plasmids. These were originally isolated from Paenibacillus ginsingari, Paenibacillus lautus and Bacillus cereus. Minimum inhibition concentrations (MICs) were carried out to determine the ability of transformed E. coli JM109 to tolerate metals at varying concentrations. Results indicated that transformed E. coli JM109 developed ability to grow in the presence of several heavy metals. Some strains were resistant to high concentrations (+10 mM) of Ni2+/Al3+, Pb2+ and Ba2+. The order of metal resistance was Ni/Al=Pb>Ba>Mn>Cr>Cu>Co=Hg. All the x transformants were sensitive to 1 mM of Co2+ and Hg2+. Moreover, protein profiling was used to determine the impact of plasmids on E. coli JM109. Proteins were extracted from both transformed and un-transformed E. coli JM109 using acetone-SDS protocol and subjected to one-dimensional (1D) and two-dimensional (2D) Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS- PAGE). Transformed E. coli JM109 were grown under the metal stress. One dimension SDS-PAGE illustrated general similarity of the profiles except for two banding positions in the 30 to 35 kDa region where bands were present in the transformants that were grown in the Ni/Al alloy containing media. Twodimensional electrophoresis PAGE analysis showed that some of the proteins were upregulated while others were down-regulated. The largest numbers of proteins were from 15 – 75 kDa. The majority of these proteins had isoelectric points (pI) between 5 and 6. It was concluded that plasmids isolated from various heavy metal-tolerant bacterial species were successfully transformed into E. coli JM109 rendering various new metal-tolerant E. coli JM109 strains. Furthermore, the study showed that metal resistance was due to the presence of the plasmids. Two-dimensional SDS-PAGE resolved more differences in the protein expression profiles. Since the plasmids rendered the E. coli JM109 tolerant to metals tested, it also can be concluded that the change in the protein profiles was due to the effects of the plasmids. Furthermore, plasmids were also re-isolated from the transformants and these plasmids were of the same size as the original ones.. All the plasmids in this study were also stably inherited, a feature associated with IncW plasmids. More detailed genetic characterization of these plasmids is required. Plasmids isolated and characterized in this study may hold biotechnology potential. Such features should be exploited in follow-up experiments.
Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

8

Hannemann, Benedikt [Verfasser], Ulf Paul [Akademischer Betreuer] Breuer, Gerhard [Akademischer Betreuer] Scharr und Frank [Akademischer Betreuer] Balle. „Multifunctional metal-carbon-fibre composites for damage tolerant and electrically conductive lightweight structures / Benedikt Hannemann ; Ulf Paul Breuer, Gerhard Scharr, Frank Balle“. Kaiserslautern : Technische Universität Kaiserslautern, 2017. http://d-nb.info/1159569517/34.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

9

Jeffery, Casey Miles. „Performance analysis of dynamic sparing and error correction techniques for fault tolerance in nanoscale memory structures“. [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0007163.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

10

Kraemer, Ute. „Nickel hyperaccumulation in the genus Alyssum L“. Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318487.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

11

Lakzian, Amir. „Diversity and metal tolerance of Rhizobium leguminosarum bv. viciae in soils contaminated with heavy metals“. Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287779.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

12

Lazkian, Amir. „Diversity and metal tolerance of Rhizobium Leguminosarum BV. Viciae in soil contaminated with heavy metals“. Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300781.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

13

Philipson, Andrew Neil. „Metal binding properties of bacteria from metal polluted soils“. Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327323.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

14

Dan, Tereza Violeta. „Phytoremediation of metal contaminated soils, metal tolerance and metal accumulation in Pelargonium sp“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58302.pdf.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

15

Phelan, Anne. „Heavy metal tolerance in Aspergillus nidulans“. Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333642.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

16

Kumar, S. „Studies on metal tolerance in plants“. Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2008. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2711.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

17

Mahmood, Shafaat. „An investigation of the sensitivity of cyanobacterial lichens to heavy metals and the induction of metal tolerance“. Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389336.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

18

Dragana, Tamindžija. „Isolation and characterization of Cr(VI) tolerant soil bacteria“. Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=110336&source=NDLTD&language=en.

Der volle Inhalt der Quelle

Annotation:

In this study, tolerance of soil bacteria to hexavalent chromium (Cr(VI)) was investigated. First, influence of high chromium levels of anthropogenic and geogenic origin on the soil cultivable bacterial community was examined. Next, a number of bacterial strains with high Cr(VI) tolerance were isolated from diverse environmental samples such as soil, sediment, water and waste material. Strains were identified and tested for the level of Cr(VI) tolerance and the ability toreduce toxic Cr(VI) to more innocuous Cr(III). Selected Bacillus cereus group strains were further characterized - their morphological and biochemical characteristics, 16S rRNA and pycA gene sequences, biofilm formation potential and resistance to other heavy metals were determined. Also, more detailed study of their tolerance level and Cr(VI) reduction was conducted. Strain with the highest resistance together with the control chromate sensitive strain were analyzed by STEM EDS for their cellular and endospore Cr content under different conditions. Results indicate Cr(VI) tolerant bacteria are present both in low and high Cr environments. Majority of isolates belonged to the B. cereus group indicating its overall high tolerance to Cr(VI). Certain strains exhibited high tolerance and reduction ability, indicating their possibleusefulness in practical bioremediation application. STEM EDS analysis of Cr(VI)-sensitive B. subtilis PY79 strain and Cr(VI)-resistant B. cereus group strain NCr1a revealed significant differences in their response to Cr(VI) and in their Cr cellular and endospore content.
U ovom radu ispitana je tolerantnost zemljišnih bakterija na šestovalentni hrom (Cr(VI)). Prvo, ispitan je uticaj visokog nivoa hroma antropogenog i geogenog porekla na kultivabilnu bakterijsku zajednicu zemljišta. Dalje, izolovani su bakterijski sojevi sa visokom tolerancijom na Cr(VI) iz različitih sredinskih uzoraka kao što su zemljište, sediment, voda i otpadni materijal. Sojevi su identifikovani i određen je nivo njihove Cr(VI) tolerancije i sposobnost redukcije toksičnog Cr(VI) u manje toksični Cr(III). Odabrani sojevi Bacillus cereus grupe su dalje karakterisani – određene su njihove morfološke i biohemijske karakteristike, 16S rDNK i pycA sekvence, potencijal formiranja biofilma i otpornost na druge teške metale. Takođe, sprovedeno je detaljnije ispitivanje njihove tolerancije i redukcije Cr(VI). Soj sa najvišom otpornošću je uporedo sa kontrolnim osetljivim sojem analiziran pomoću STEM EDS na sadržaj hroma u ćelijama I endosporama u različitim uslovima. Rezultati ukazuju da su bakterije tolerantne na Cr(VI) prisutne i u sredinama sa niskim i sa visokim koncentracijama hroma. Većina izolata pripadala je B. cereus grupi što ukazuje na njenu uopšteno visoku otpornost na Cr(VI). Pojedini sojevi su pokazali visoku otpornost i sposobnost redukcije Cr(VI), što ukazuje na mogućnost njihove praktične primene u bioremedijaciji. STEM EDS analiza osetljivog B. subtilis PY79 soja i Cr(VI)- rezistentnog soja B. cereus grupe NCr1a otkrila je značajne razlike u njihovom odgovoru na Cr(VI) i sadržaju Cr u njihovim ćelijama i endosporama.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

19

MacDonald, Hazel. „Heavy metal tolerance in filamentous green algae“. Thesis, University of the West of Scotland, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329824.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

20

Turner, Andrew Paul. „The tolerance of trees to metal pollution“. Thesis, Liverpool John Moores University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304542.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

21

Aelst, Sébastien van. „Etude fonctionnelle des gènes plasmidiques de résistance au cuivre de Cupriavidus metallidurans: aspects physiologique, biochimique et écologique“. Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210529.

Der volle Inhalt der Quelle

Annotation:

Cupriavidus metallidurans CH34 est la bactérie Gram négative considérée comme organisme-modèle pour l’étude de la résistance aux métaux lourds. Notre travail a porté sur sa résistance au cuivre, codée par les gènes cop du plasmide pMOL30. Ces gènes, responsables des différentes étapes de la résistance (compartimentation des systèmes d’efflux entre périplasme et cytoplasme, modification de valence, et d’autres fonctions totalement inconnues) ont suscité notre intérêt.

On distingue dans l’îlot cop des gènes codant pour des fonctions de résistance proprement dite (essentiellement par détoxication active du cytoplasme et du périplasme). En effet, les mutants de copSRABCD, copF, et dans une moindre mesure copJ et copE deviennent sensibles. Les phénotypes des mutants divergent toutefois suivant que la mutation soit sur un cosmide qui ne porte que l’îlot (pMOL1024) ou dans son plasmide d’origine (pMOL30). Un second groupe de mutants (copVTMK, copG, copL, copQ) se distingue par un phénotype plus résistant ou identique à la souche parente, sauf autour de la CMI. Ces gènes interviendraient donc à la CMI pour assurer la résistance la plus élevée et le maintien d'un état viable latent.

La présence de l’îlot cop permet de contenir le taux d’oxygène radicalaire qui reste à un taux basal lorsque les cellules sont adaptées au cuivre environnent. Après un choc de Cu (ou stress aigu), l’îlot cop répond de façon « explosive » au stress, en consommant l’énergie du potentiel membranaire et en augmentant fortement l’activité de la chaîne respiratoire.

La résistance au cuivre est inductible, mais de façon différenciée pour la souche sauvage (CH34) et celle qui ne porte qu l’îlot cop (AE1744) :la CMI de CH34 triple après adaptation au cuivre, alors que celle d’AE1744 est inchangée. Après un choc de Cu, la résistance au cuivre est plus fortement induite pour AE1744 que pour CH34. Ces observations suggèrent que l’îlot cop ait été sélectionné pour sa capacité à répondre à un stress aigu puis intégré dans un ensemble de gènes plus vaste qui répond à des impératifs de stress chronique.

L’analyse biochimique de CopI, une petite protéine bleue à cuivre, montre qu’elle porte un site analogue à celui des oxydases multicuivre. Son rôle pourrait dès lors être celui d’une réductase multicuivre. La protéine CopK lie de façon très spécifique le Cu(I) et il semble que la liaison du cuivre modifie sa structure. L’analyse écologique a montré que des homologues de copK pourraient être présents dans l’ADN extrait de la terre de biotopes chargés en cuivre, et dans les souches cuprorésistantes qu’on y trouve.

La contribution majeure de cette thèse est de montrer que l’effet d’un stress métallique ne se résume pas à deux états physiologiques « mort ou vif ». Il y a lieu de considérer des états transitoires (choc de Cu, adaptation au métal, survie autour de la CMI, persistance) où interviennent des gènes spécifiques dans un ou plusieurs états donnés. Les résultats biochimiques et physiologiques ne nous éclairent pas encore assez sur les interconversions Cu(I)/Cu(II) ni sur les flux de cations notamment vers l'espace extracellulaire. Cette thèse ouvre des perspectives sur des mécanismes (protection à la CMI, phénotype persistant) assurant la survie des bactéries ou leur potentiel de recolonisation lors d'une diminution de la pression toxique :les gènes copT, copV, copK, copM, copB, copG, copL et copQ semblent impliqués dans ces fonctions.

Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO und andere Zitierweisen

22

Pati, Nishikanta Guturu Parthasarathy. „Occlusion tolerant object recognition methods for video surveillance and tracking of moving civilian vehicles“. [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-5133.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

23

Bleackley, Mark Robert. „Transition metal tolerance and the Saccharomyces cerevisiae genome“. Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/30821.

Der volle Inhalt der Quelle

Annotation:

Transition metal ions are essential nutrients to all forms of life. Iron, copper, zinc, manganese, cobalt and nickel all have unique chemical and physical properties that make them attractive molecules for use in biological systems. Many of these same properties that allow these metals to provide essential biochemical activities and structural motifs to a multitude of proteins including enzymes and other cellular constituents also leads to a potential for cytotoxicity. Organisms have been required to evolve a number of systems for the efficient uptake, intracellular transport, protein loading and storage of metal ions to ensure that the needs of the cells can be met while minimizing the associated toxic effects. The yeast Saccharomyces cerevisiae has been used as model organism for the investigation of these systems and a majority of the genes and biological systems that function in yeast metal homeostasis are conserved throughout eukaryotes to humans. Traditionally, genomic studies in metal homeostasis focus on the response to one, or in some cases two, metals. Here, I have used high density yeast arrays of a S. cerevisiae deletion collection to study the genes required for tolerance to six transition metals in parallel and I have used this data to examine the role of genes not only in the homeostasis of individual metals but to also gain insight into cellular transition metal homeostasis as a whole. Genes and pathways with novel function in the homeostasis of a particular metal have been identified along with the systems that function with broad spectrum metal specificity. Data generated in this screen has also be combined with previously published data sets that examine different aspects of yeast biology in an attempt to delve deeper in to the cellular machinery that allows yeast, and potentially the cells of other organisms, to maintain the balance between metal ions as essential nutrients as opposed to toxic moieties. Metallochaperones represent a relatively recent emerging class of proteins that play a central role in maintaining this balance. As part of the analysis of the high density array screens, putative chaperones have been identified. Additionally a yeast 2 hybrid screen using a cytoplasmic domain of the S. cerevisiae high affinity iron transporter Ftr1p has been performed to with the goal of discovering candidate iron chaperones. As a whole, the research discussed in this thesis has shed light on a number of new features of the homeostatic mechanisms that function in S. cerevisiae and will provide the basis for further investigation into the interactions between cells and metal ions eventually leading to implications in human health and disease.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

24

Lowell, Christina, und Christina Lowell. „Thermo-acidophilic Algae: pH and Metal Tolerances“. Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12361.

Der volle Inhalt der Quelle

Annotation:

The class Cyanidiophyceae (the "cyanidia") includes three genera, the walled Cyanidium and Galdieria and the "naked" Cyandioschyzon. All of these algae are unicellular and asexual and live at high temperature and low pH. The cyanidia grow optimally at a pH of 2-3 but can tolerate a higher pH and lower their surrounding pH if it is above the optimal level. They can also tolerate high concentrations of potential toxins that are often found in their natural environments. This thesis shows that strains of cyanidia from Yellowstone National Park and other geographic locations have differing abilities to lower their surrounding pH and tolerate environmental toxins that are found in many environments in which they live. These unique characteristics of this class of algae allow them to be optimally adapted for life in extreme environments with few competitors. This thesis includes unpublished co-authored material.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

25

Watmough, Shaun A. „Adaptation to pollution stress in trees : metal tolerance traits“. Thesis, Liverpool John Moores University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260825.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

26

Sewell, Andrew Kelvin. „The mechanism of heavy metal tolerance in higher plants“. Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333676.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

27

Anderson, Craig. „Mechanistic bases of metal tolerance : linking phenotype to genotype“. Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/43776/.

Der volle Inhalt der Quelle

Annotation:

Ecotoxicology is currently undergoing a revolution as the result of new technological advances in molecular biology, capable of finely resolving metabolic mechanisms associated with exposure. These high-throughput analyses can detail the evolutionary and ecological implications of exposure in non-model organisms, such as the earthworm, Lumbricus rubellus. This terrestrial sentinel has been observed across former mine sites that are highly contaminated with arsenic and have been found to mitigate toxicity at soil concentrations that cause mortality in unadapted individuals. This is indicative of the adaptive capacity of natural populations recently exposed to persistent and strong selection pressure. However, mechanisms surrounding adaptation to arsenic in L. rubellus have yet to be characterised, and so the effects of exposure are broadly reported with the aim of distinguishing resistance from phenotypic plasticity in natural populations. Unadapted earthworms were initially used to derive basal phenotypic variation associated with arsenic exposure. Variation in life-history parameters was observed among adult and juvenile L. rubellus, establishing relative sensitivity and population-level inferences. A systems biology approach was employed to describe molecular mechanisms associated with arsenic metabolism, encompassing transcriptomic and metabolomic analyses, underpinned by arsenic speciation. Insight into the genetic bases of arsenic resistance, which enable persistence of L. rubellus at highly contaminated sites, was sought. Recombinant inbred lineages derived from adapted populations, were cultivated and their phenotypes relative to arsenic exposure determined. Phylogeographic analyses were used to interrogate genetic variation among populations inhabiting former mine sites as well as proximal control sites. A mitochondrial marker defined cryptic species across the UK, but did not establish soil chemical profiles relative to clade occurrence. RADseq better resolved genetic variation at these sites, determining that soil geochemistry is strongly associated with genetic variation. Furthermore, genomic markers inferred genetic erosion, found to selectively reduce variation at sites relative to a single clade.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

28

Jobling, M. G. „Physical and genetic analysis of heavy metal resistance plasmids“. Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372683.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

29

Ivorra, i. Castellà Núria. „Metal induced succession in benthic diatom consortia“. [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/56237.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

30

Al-Hiyaly, Sedik A. K. „Evolution of zinc tolerance under electricity pylons“. Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257133.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

31

Hughes, Ruth. „Serpentine tolerance in the Mimulus guttatus complex“. Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286489.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

32

Fiore, Marli de Fatima. „Isolation of Brazilian Amazon cyanobacteria and further characterization for metal tolerance“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0017/NQ55624.pdf.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

33

Walker, Paul L. „Genotypic and phenotypic aspects of metal tolerance in Holcus lanatus L“. Thesis, University of Sheffield, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284588.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

34

Cooley, R. N. „Studies of nitrate assimilation and heavy metal tolerance in Aspergillus nidulans“. Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372691.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

35

Siriwardena, P. P. G. S. N. „Tolerance and early life stages of Tilapia (Cichlidae:Tilapiini) to metal stress“. Thesis, University of Stirling, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384838.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

36

Harper, Frances Anne. „The cost of copper tolerance in Mimulus guttatus“. Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307278.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

37

Dechamps, Caroline. „Biologie des populations de Thlaspi caerulescens: étendue et structuration de la variation génétique et de la plasticité phénotypique de populations métallicoles et non métallicoles“. Doctoral thesis, Universite Libre de Bruxelles, 2008. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210522.

Der volle Inhalt der Quelle

Annotation:

Les travaux entrepris au cours de cette thèse visaient à répondre à des questions fondamentales sur la biologie évolutive des plantes adaptées aux sols contaminés par des métaux lourds. À travers une approche comparative de populations métallicoles (M :sur sols métallifères) et non métallicoles (NM :sur sol normal) de l’espèce modèle Thlaspi caerulescens, cette thèse avait donc pour objectif général d’appréhender l’adaptation aux habitats métallifères d’une manière plus globale que par le seul trait de tolérance aux métaux. Nous avons donc cherché à mettre en évidence les différences de stratégie de vie entre les populations M et NM. Nous avons également estimé le coût de l’adaptation à l’environnement métallifère. Enfin, nous avons porté une attention particulière au rôle que pouvait jouer la plasticité dans l’adaptation à l’environnement métallifère. Cette plasticité a été considérée au niveau des traits d’histoire de vie et du système racinaire.

Trois expériences ont étudié les variations des traits d’histoire de vie des populations M et NM: (1) une culture en conditions contrôlées des populations sur un gradient de concentrations en Zn, (2) une expérience de transplantation réciproque in situ de populations M et NM et (3) un suivi démographique dans les populations M et NM. Enfin, une quatrième expérience (4) visait à évaluer les variations entre populations M et NM d’un trait particulier :la plasticité du système racinaire en réponse à une distribution hétérogène des métaux dans le sol.

Nos résultats montrent que les plantes M ont, en moyenne, des cycles de vie plus courts que les plantes NM (exp. 1, 3). Par ailleurs, les populations M sont capables de modifier leur stratégie de reproduction en fonction des teneurs en métaux dans le sol ou du site de transplantation (métallifère vs. non métallifère). Que ce soit sur des substrats non contaminés en Zn (exp. 1) ou sur des sites non métallifères (exp. 2), les plantes M produisent autant de graines au cours de leur vie que les plantes NM. Ces résultats suggèrent l’absence d’un coût adaptatif fort chez les plantes M. In situ (exp. 3), nous avons mis en évidence un effet structurant de l’hétérogénéité spatiale des sites métallifères sur les stratégies de vie des plantes M. Enfin, les plantes M ont exprimé une plasticité plus élevée du comportement d’exploration racinaire que les plantes NM (exp. 4).

L’existence de stratégies de vie plastiques, l’homéostasie de la fitness sur une large gamme de concentrations en Zn, ainsi que le faible coût adaptatif mis en évidence chez les populations M suggèrent que ces populations sont plus aptes à fonder de nouvelles populations que les populations NM. Nos résultats ont également clairement démontré que les populations M sont caractérisées par une plasticité plus élevée que les populations NM (génotype généraliste). Cette plasticité concerne à la fois les stratégies de vie et les mécanismes d’exploration racinaire. Cette plasticité élevée des plantes M a très probablement évolué en réponse à l’hétérogénéité spatiale des sites métallifères La sélection de génotypes généralistes sur les sites métallifères est une piste de recherche qui mérite, à présent, d’être approfondie chez les autres espèces colonisant les sites métallifères.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO und andere Zitierweisen

38

Thompson, Jill. „Population biology of Anthoxanthum odoratum, Plantago lanceolata and Rumex acetosa on zinc and lead mine spoil“. Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329462.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

39

Whitebrook, J. „Heavy metal tolerance and the distribution in SW Britain of the diploid and tetraploid cytotypes of Leucanthemum vulgare Lam. (Compositae)“. Thesis, University of Bristol, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372036.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

40

Piola, Richard Fabio Biological Earth &amp Environmental Sciences Faculty of Science UNSW. „Differential tolerance of introduced & native marine invertebrates to heavy metal pollution“. Publisher:University of New South Wales. Biological, Earth & Environmental Sciences, 2007. http://handle.unsw.edu.au/1959.4/40673.

Der volle Inhalt der Quelle

Annotation:

In near-shore marine environments, two of the most prevalent anthropogenic disturbances affecting ecosystem diversity and function are the invasion of exotic species, and the release of toxic chemicals. Estuarine and harbour environments worldwide are dually subjected to high levels of toxic disturbance and ever increasing rates of invasion, via activities such as boating and shipping. It is not clear, however, whether the success of invasive species is influenced by the presence of toxic contaminants in these impacted environments. In particular, nonindigenous marine species (NIS) may be advantaged in chemically disturbed environments if they are more tolerant of toxicants. This thesis examines whether nonindigenous and native sessile invertebrate species have differential tolerance to a common aquatic contaminant, copper (Cu), which has links to both the invasion process (via its use in antifouling paints and the vector of hull fouling) and the modification of recipient environments (via human-mediated pollution). A series of laboratory- and field-based experiments showed that the cosmopolitan invasive bryozoans Watersipora subtorquata, Bugula neritina and Schizoporella errata are highly tolerant of copper pollution. The larvae and adults of W. subtorquata and B. neritina in particular were able to survive and grow in copper-polluted environments far exceeding most observed real-world levels (< 100 /??g 1-1). These nonindigenous species also showed very strong postexposure recovery. In contrast, the co-occurring native bryozoans Celleporaria nodulosa and Fenestrulina mutabilis demonstrated comparatively low tolerance to copper, with markedly reduced survival and fitness under Cu contaminated conditions, and inferior recovery abilities post-exposure. These findings were further supported by a long-term manipulative field experiment, examining the effect that varying levels of Cu exposure have on the structure and diversity of developing sessile invertebrate assemblages. Cu exposure decreased native species diversity by up to 50%, yet had no effect on NIS numbers. Consequently, in the presence of copper contamination, NIS dominated sessile communities, often resulting in substantial changes to community structure. Important insights were also gained into the nature of metal tolerance in NIS. Toxicity studies on larvae of the introduced bryozoan Bugula neritina revealed intraspecific differences in tolerance to Cu, associated with the level of pollution experienced by the adult source populations. There was also evidence of fitness costs related with increased Cu tolerance. In summary, we have found evidence that the success of invasive species is influenced by chemical contamination. NIS may be advantaged in contaminated estuaries relative to native species and this may assist in their establishment and persistence in new habitats.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

41

Pires, Carlos. „Bacteria in heavy metal contaminated soil : diversity, tolerance and use in remediation“. Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/5581.

Der volle Inhalt der Quelle

Annotation:

The objectives of this project were to determine the bacterial diversity in a heavily contaminated metal region of Portugal. Both traditional and molecular based methods were used to identify tolerant strains and species. The most tolerant species were subsequently identified and utilized for examining the potential for using them to immobilize specific metals from contaminated waste streams by comparing different support materials. Heterotrophic bacterial populations were isolated and characterized from a contaminated industrial area in Northern Portugal. In a first sampling, 278 strains were isolated in different solid media. To assess the diversity of this ecological site and to select representative strains, the isolates were screened by using Random Amplified Polymorphic DNA (RAPD)-PCR profiles. Phenotypic characterization, phylogenetic analysis by sequencing the 16S rRNA genes and metal tolerance tests with zinc (Zn), cadmium (Cd) and arsenic (As) were performed with the selected strains. Recovered gram-positive isolates were related to class Actinobacteria and Bacilli. The majority of the isolates were related to genera Microbacterium and Bacillus. Strains from the genus Arthrobacter were also well represented. 16S rRNA gene sequence similarity of the gram-negative isolates showed that they were related to classes γ-Proteobacteria, ß-Proteobacteria, a-Proteobacteria and Flavobacteria. The most frequently isolated taxa were γ-Proteobacteria, related with the genus Pseudomonas, where a large number of isolates were clustered. These genera are common in metal contaminated environments. Many of the strains (approx. 17) had a high level of tolerance to the heavy metals tested. A total of 13 isolates were not able to grow when metals were present. In a second sampling the soil rhizosphere was screened for bacterial populations, using metal-based selective media for isolation. About 42 strains were recovered when metal supplemented media was used. The gram-positive population were predominantly Bacilli and Actinobacteria members. Bacillus, Microbacterium and Arthrobacter were the most common gram-positive genera. Gram-negative genera were from the same classes as in the first sampling however Sphingobacteria was present. γ-Proteobacteria and ß-Proteobacteria were the most common taxa. The isolates were shown to be very resistant to Zn and As, with about half of the isolates able to grow with Cd present. Interestingly, no strains could grow in the presence of metal mixtures. Despite the number of strains recovered in both samplings the majority of the isolates were clustered within a very small number of genera. During the sampling periods two strains showing low similarity to other bacteria were isolated. These strains were characterized and studied in detail justifying their classification as representing two novel species of the genus Chryseobacterium. The names proposed for these organisms are Chryseobacterium palustre sp. nov. (type strain 3A10[type strain]) and Chryseobacterium humi sp. nov. (type strain ECP37[type strain]). Three isolates 1C2, 1ZP4 and EC30 belonging to genera Cupriavidus, Sphingobacterium and Alcaligenes respectively, showing high tolerance to heavy metals, were selected for further study in immobilised systems for Zn and Cd removal. In most cases, matrices (alginate, pectate and a synthetic cross-linked polymer) with immobilised bacteria showed better metal removal. 1C2, a strain belonging to the Cupriavidus genera, was able to increased the removal of Zn; EC30, a bacteria related to Alcaligenes, was the most promising candidate for Cd removal, especially when combined with the synthetic polymer. Removal of metals as single or in binary mixtures was also assessed. Cd removal was most effective when single metal solutions were tested using immobilised bacteria and examining metal matrixes. Based on the strains used and the matrices tested, best results were obtained for removal of Zn from binary mixtures with Cd. Potential exists for further studies to exploit these bacterial strain to develop effective bioremediation approaches for the removal of heavy metals from waste water streams.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

42

Tilstone, Gavin H. „The significance of multiple metal tolerance in Mimulus guttatus Fischer ex DC“. Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337730.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

43

Chang, Po-Yu. „Modeling of fatigue behavior and damage tolerance/durability in fiber metal laminates“. Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1608577901&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

44

Fasola, Emanuele. „Acquisition and inheritance of tolerance to metals in anurans“. Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22226.

Der volle Inhalt der Quelle

Annotation:

Doutoramento em Biologia
Os anfíbios encontram-se em declínio a nível global, sendo a contaminação química um dos principais fatores associados a este declínio. De facto, a exposição de populações de anfíbios a este tipo de perturbações ambientais pode provocar a perda de diversidade genética, devido à diminuição de: 1) aptidão, 2) plasticidade ambiental e 3) eficácia dos mecanismos de tolerância. A contaminação por metais é uma das causas de poluição mais comum no mundo, estando presente em larga escala na Península Ibérica, nomeadamente na Faixa Piritosa Ibérica. Deste modo o estudo dos mecanismos de tolerância a metais, em anfíbios, é relevante, assim como a investigação sobre os mecanismos de hereditariedade desta tolerância. Um dos objetivos do presente trabalho centrou-se no estudo da hereditariedade de tolerância a metais em ovos de Pelophylax perezi. Os resultados obtidos sugerem uma dominância genética incompleta como sendo o mecanismo mais provável de hereditariedade de tolerância a contaminação por metais, em ovos de P. perezi. Estes resultados suportam a hipótese de hereditariedade de tolerância recessiva (ou dominância incompleta). Neste contexto, uma perda de diversidade genética em populações de anfíbios, expostas a contaminação por metais pode ocorrer, mesmo que a fixação de alelos na população seja excluída. De modo a estudar a possibilidade de girinos adquirirem maior tolerância a contaminação por metais, devido à sua exposição histórica a este tipo de contaminação, foram recolhidos girinos de P. perezi em locais contaminados por metais e em locais de referência. Posteriormente, os girinos foram expostos, em laboratório, a um pulso de contaminação intensa por metais. Os girinos oriundos de locais contaminados não mostraram maior tolerância à toxicidade letal de metais comparativamente aos girinos recolhidos em locais de referência. Mais ainda, não revelaram estar sujeitos a um maior stress oxidativo. No entanto, a quantidade de metais no corpo provou a contaminação por metais nos locais historicamente impactados e mostrou que os iões de mercúrio e chumbo são prontamente biodisponíveis para os girinos de P. perezi. Os girinos de locais contaminados apresentaram níveis constitutivos de metalotioneínas, superiores aos medidos nos girinos recolhido os nos locais de referência, o que pode indicar adaptação a contaminação por metais. Por fim, o último objetivo consistiu em avaliar a influência de contaminação química na composição e diversidade do microbioma da pele de populações de P. perezi bem como, identificar a sua sensibilidade a contaminação por efluentes de drenagem ácida. O microbioma da pele dos anfíbios apresenta um papel fundamental na proteção destes organismos a agentes perturbadores ambientais. Os resultados obtidos revelaram que os metais podem influenciar a composição da comunidade microbiana de anfíbios que habitam locais contaminados. Mais ainda, uma concentração elevada de efluente de drenagem mineira inibiu o crescimento da maioria dos isolados de bactérias da pele dos anfíbios. Esta inibição pode sugerir que os anfíbios perdem uma fração importante do seu microbioma e consequentemente, afetar a proteção da sua pele, quando expostos a contaminação por metais, o que pode determinar um aumento da sensibilidade a este tipo de contaminação.
Amphibians are declining globally, chemical contamination being one of the major factors driving this process. As a consequence of exposure to such environmental perturbation, natural population of amphibians may lose their genetic diversity, which may occur due to a decrease in: 1) fitness, 2) environmental plasticity capabilities and 3) tolerance mechanisms efficiency. Metal contamination is one of the most worldwide distributed contamination source, having a great impact in the Iberian Peninsula habitats, especially in the Iberian pyrite belt region. Therefore, is important to explore how tolerance mechanism, toward metal contamination, work in amphibians and how genetically determined tolerance mechanisms are inherited. In this work, these topics were addressed by assessing the inheritance to lethal tolerance to acid mine drainage and copper contamination in eggs of the Perez's frog Pelophylax perezi. Incomplete dominance was found to be the most likely inheritance mechanism of tolerance toward these two chemical stressors in the eggs of P. perezi. The results support the recessive (or incompletely dominant) tolerance inheritance (working-) hypothesis. Thus, the amphibians’ populations impacted by metal contamination can considerably lower their genetic diversity, even if allele fixation was excluded. The possibility of tadpoles, historically exposed to metal contamination, being able to acquire an increased tolerance to metal contamination, comparatively to tadpoles inhabiting reference sites, was also studied. Pelophylax perezi tadpoles, sampled at historically metal impacted mining sites, did not show higher oxidative stress or lethal tolerance comparatively to tadpoles inhabiting reference sites. However, the metal body burden proved metal contamination at the historically metal impacted sites and showed that mercury and lead ions are readily bioavailable for P. perezi tadpoles. Furthermore, tadpoles from metal contaminated sites seem to show higher constitutive levels of metallothioneins, which may suggest adaptation to metal contamination The last objective of this work, was to evaluate the influence, of metal contamination, on the composition and diversity of the P. perezi skin microbiome, and to explore its tolerance to acid mine drainage contamination. Amphibians’ skin microbial community has been shown to help its hosts tolerating infections. Because the increasing research on the important protective role of amphibians’ skin microbiome, its diversity and capacity to tolerate metal contamination was as well investigated. Obtained results showed that metal contamination influences the skin microbial community composition in frogs living at metal impacted sites; furthermore, an intense acid mine drainage concentration can inhibit the growth of almost all the isolated strains. This inhibition suggests that amphibians may lose an important part of their skin microbiome, affecting the protection of their skin, when exposed to metal contamination; which, in turn may lead to an increased sensitivity to metal contamination.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

45

Johnson, Dallas W. „Metal tolerance, survival characteristics and nodulating abilities of isolates of Rhizobium leguminosarum biovar trifolii from Sudbury reclaimed, metal-contaminated soils“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0004/MQ31441.pdf.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

46

Ribeiro, Manuella Nóbrega Dourado. „Burkholderia sp. cadmium tolerance mechanism and its influence in phytoremediation“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11151/tde-17122013-144639/.

Der volle Inhalt der Quelle

Annotation:

Soils have been contaminated with cadmium (Cd) by the use of fertilizers, calcareous, pesticides and industrial and/or domestic effluents. It can be leached to groundwater, as well as be taken up by plants potentially leading to reduce growth and yield. It causes different damages to the cell, generating oxidative stress which is responsible for its toxicity, affecting all living organism. A balance in the redox state of the cell to maintain cellular integrity and metabolism is essential for organism tolerance. Thus, the antioxidant response of bacteria exposed to Cd was studied to understand the tolerance mechanism, and be able to develop a methodology to bioremediate contaminated soils. MDA and hydrogen peroxide contents and different enzymes activity of antioxidant system (SOD, CAT, GR and GST) of two strains from Burkholderia genus, one from a soil contaminated with Cd in high concentrations (strain SCMS54) and the other from soil without Cd (strain SNMS32) in two exposure time (5 and 12 h), were analyzed. Stress measurement (MDA and hydrogen peroxide content) and antioxidant enzyme activities (SOD, CAT, GR and GST) increased in almost all treatments in the presence of Cd. These results also indicate that strain SCMS54 (isolated from Cd contaminated soil) presents a higher metabolic diversity and plasticity due the expression of more isoforms of the enzymes SOD, CAT and GR. The strain also accumulates 50% more Cd. We also analyzed the response to Ni of these two strain, observing a similar response to Cd, except for GST enzyme expression, which in strain SCMS54 this enzyme was induced in the presence of Ni, indicating that this enzyme can be essential on Ni tolerance. After that, the strain isolated from Cd contaminated soil (SCMS54) was selected to proceed the studies to evaluate the benefits of tolerant microorganism-tomato plant interaction. The use of plants to remove heavy metals from contaminated soilhas less impact and a lower cost. Soil microorganisms can be able to solubilize or mobilize soil metals acting also as bioremediator. Besides the high tolerance to Cd, the strain SCMS54 can produce indole-acetic acid (IAA), solubilize inorganic phosphate and produce siderophore, revealing its potential in plantmicroorganism mutual and beneficial interaction. When interacting with tomato plants exposed to Cd, this bacterium led to decrease in plant peroxide concentration and chlorosis levels, promoted relative plant growth and reduced the root absorption of Cd resulting in an increase in plant tolerance to this highly toxic heavy metal. Indicating that inoculation of tomato plants with Burkholderia sp. SCMS54 promotes better growth when cultivated in the presence of Cd by a mechanism that appears to decrease Cd concentration in roots as a result of a bacterial-plant root beneficial interaction.
O cádmio (Cd) tem contaminado solos pelo uso de fertilizantes, calcário, agrotóxicos e resíduos industriais e/ou domésticos. Podendo ser lixiviado ao lençol freático ou absorvido pelas plantas,resultando na redução do crescimento e da produtividade. Esse metal afeta todos os organismos vivos e causa diferentes danos às células. A tolerância a esse metal se deve principalmente ao balanço do estado redox da célula para manter a integridade celular e metabolismo.Assim, foram isoladas bactérias de solo contaminado e não contaminado com Cd, selecionando isolados tolerantes a altas concentrações de diferentes metais (Cd, Ni e Zn), em seguida, foi observado a resposta do sistema antioxidante da bactéria na presença do Cd, a fim de auxiliar no desenvolvimento de metodologias para biorremediar solos contaminados. Foi quantificado MDA e peróxido de hidrogênio e a atividade de diferentes enzimas do sistema antioxidante (SOD, CAT, GR e GST) de duas estirpes do gênero Burkholderia tolerantes a todos os metais testados, uma isolada do solo contaminado com altas concentrações de Cd (estirpe SCMS54) e a outra do solo sem Cd (estirpe SNMS32) em dois tempos de exposição (5 e 12 h). Na estirpe SCMS54, as medidas de estresse (peroxidação lipídica e peróxido de hidrogênio) e a atividade das enzimas antioxidantes (SOD, CAT, GR e GST) da maioria dos tratamento com cádmio aumentaram, esta estirpe também expressa mais isoformas de SOD, CAT e GR, além de acumular 50% mais Cd. Esses resultados mostram que a estirpe SCMS54 (isolada do solo contaminado com Cd) apresenta uma maior diversidade metabólica e plasticidade. Foram analisadas também a resposta dessas duas estirpes ao Ni, observando uma resposta semelhante ao Cd, exceto na expressão da enzima GST, que no estirpe SCMS54 foi induzida na presença do Ni, indicando que essa enzima pode ser essencial na tolerância ao Ni. Portanto, a estirpe isoladado solo contaminado com Cd (SCMS54) foi selecionada para prosseguir os estudos e avaliar os benefícios da interação entre microrganismos tolerantes-plantas de tomate na fitorremediação. Essa técnica é usada remover para metais pesados do solo com um menor impacto e baixos custos. Os microrganismos do solo podem solubilizar e mobilizar metais do solo, atuando como biorremediador. Além da alta tolerância ao Cd, a estirpe SCMS54 produz ácido indol acético (AIA), solubiliza fosfato inorgânico e produz sideroforo, mostrando seu potencial na interação benéfica planta-microorganismo. Quando interagindo com as plantas de tomate expostas ao Cd, essa bactéria diminui a concentração de peróxido da planta e a clorose ocasionado pelo Cd,e reduz a absorção de Cd pela raiz resultando em um aumento da tolerância da planta ao metal pesado altamente tóxico. Assim, a inoculação de plantas de tomate com Burkholderia sp. SCMS54 promove crescimento da planta na presença de Cd, desencadeando um mecanismo que diminui a concentração de Cd nas raízes devido a essa interação benéfica bactéria-raiz da planta.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

47

Lock, S. J. „Water-tolerant organometallic reactions : nucleophilic additions to carbonyl compounds using allyl metals in aqueous solution“. Thesis, Swansea University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637942.

Der volle Inhalt der Quelle

Annotation:

Against a background of the reactivity of traditional organometallics, this work describes nucleophilic addition reactions that take place via the intervention of metals in the presence of water. The experimental work focuses on allylation of aldehydes in water-containing solvents using nickel, bismuth and aluminium. Chapter 1 outlines the current influence of environmental issues on the practice of chemistry and the value of water as a solvent. Carbon-carbon bond formation is discussed in the context of mechanism and common methods are reviewed, particularly with respect to reaction of the carbonyl functional group. A sample of the well-established organometallic reagents are examined in terms of their characteristics and general reactivity, which then serve as a backdrop to a description of the types of metal-mediated reactions that occur in aqueous solutions. Chapter 2 describes allylation reactions using water-tolerant allylic metals species obtained via transmetallation between metal salts and allylic Grignard reagent. The properties and reactions of a nickel-containing allylating agent are examined in greater detail. Chapter 3 describes bismuth-mediated reactions in which zero-valent bismuth is generated in situ from a bismuth salt and a reducing metal in entirely aqueous solution. Chapter 4 examines the potential of using aluminium to promote allylation reactions in aqueous solutions. Chapter 5 focuses on allylations using bismuth powder in entirely aqueous solutions and the influences of a variety of additives. The scope and mechanism of reactions performed in potassium fluoride solution are explored in more detail.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

48

Nyberg, Berglund Anna-Britt. „Postglacial colonization and parallel evolution of metal tolerance in the polyploid Cerastium alpinum /“. Uppsala : Dept. of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200565.pdf.

Der volle Inhalt der Quelle

APA, Harvard, Vancouver, ISO und andere Zitierweisen

49

Kachenko, Anthony. „Ecophysiology and phytoremediation potential of heavy metal(Loid) accumulating plants“. Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/6348.

Der volle Inhalt der Quelle

Annotation:

Soil contamination with heavy metal(loid)s is a major environmental problem that requires effective and affordable remediation technologies. The utilisation of plants to remediate heavy metal(loid)s contaminated soils has attracted considerable interest as a low cost green remediation technology. The process is referred to as phytoremediation, and this versatile technology utilises plants to phytostabilise and/or phytoextract heavy metal(loid)s from contaminated soils, thereby effectively minimising their threat to ecosystem, human and animal health. Plants that can accumulate exceptionally high concentrations of heavy metal(loid)s into above-ground biomass are referred to as hyperaccumulators, and may be exploited in phytoremediation, geobotanical prospecting and/or phytomining of low-grade ore bodies. Despite the apparent tangible benefits of utilising phytoremediation techniques, a greater understanding is required to comprehend the ecophysiological aspects of species suitable for phytoremediation purposes. A screening study was instigated to assess phytoremediation potential of several fern species for soils contaminated with cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn). Hyperaccumulation was not observed in any of the studied species, and in general, species excluded heavy metal uptake by restricting their translocation into aboveground biomass. Nephrolepis cordifolia and Hypolepis muelleri were identified as possible candidates in phytostabilisation of Cu-, Pb-, Ni- or Zn-contaminated soils and Dennstaedtia davallioides appeared favourable for use in phytostabilisation of Cu- and Zn-contaminated soils. Conversely, Blechnum nudum, B. cartilagineum, Doodia aspera and Calochlaena dubia were least tolerant to most heavy metals and were classified as being least suitable for phytoremediation purposes Ensuing studies addressed the physiology of arsenic (As) hyperaccumulation in a lesser known hyperaccumulator, Pityrogramma calomelanos var. austroamericana. The phytoremediation potential of this species was compared with that of the well known As hyperaccumulator Pteris vittata. Arsenic concentration of 3,008 mg kg–1 dry weight (DW) occurred in P. calomelanos var. austroamericana fronds when exposed to 50 mg kg–1 As without visual symptoms of phytotoxicities. Conversely, P. vittata was able to hyperaccumulate 10,753 mg As kg–1 DW when exposed to 100 mg kg–1 As without the onset of phytotoxicities. In P. calomelanos var. austroamericana, As was readily translocated to fronds with concentrations 75 times greater in fronds than in roots. This species has the potential for use in phytoremediation of soils with As levels up to 50 mg kg–1. Localisation and spatial distribution of As in P. calomelanos var. austroamericana pinnule and stipe tissues was investigated using micro-proton induced X-ray emission spectrometry (µ-PIXE). Freeze-drying and freeze-substitution protocols (using tetrahydrofuran [THF] as a freeze-substitution medium) were compared to ascertain their usefulness in tissue preservation. Micro-PIXE results indicated that pinnule sections prepared by freeze-drying adequately preserved the spatial elemental distribution and tissue structure of pinnule samples. In pinnules, µ-PIXE results indicated higher As concentration than in stipe tissues, with concentrations of 3,700 and 1,600 mg As kg–1 DW, respectively. In pinnules, a clear pattern of cellular localisation was not resolved whereas vascular bundles in stipe tissues contained the highest As concentration (2,000 mg As kg–1 DW). Building on these µ-PIXE results, the chemical speciation of As in P. calomelanos var. austroamericana was determined using micro-focused X-ray fluorescence (µ-XRF) spectroscopy in conjunction with micro-focused X-ray absorption near edge structure (µ-XANES) spectroscopy. The results suggested that arsenate (AsV) absorbed by roots was reduced to arsenite (AsIII) in roots prior to transport through vascular tissues as AsV and AsIII. In pinnules, AsIII was the predominant species, presumably as aqueous-oxygen coordinated compounds. Linear least-squares combination fits of µ-XANES spectra showed AsIII as the predominant component in all tissues sampled. The results also revealed that sulphur containing thiolates may, in part sequester accumulated As. The final aspect of this thesis examined several ecophysiological strategies of Ni hyperaccumulation in Hybanthus floribundus subsp. floribundus, a native Australian perennial shrub species and promising candidate in phytoremediation of Ni-contaminated soils. Micro-PIXE analysis revealed that cellular structure in leaf tissues prepared by freeze-drying was adequately preserved as compared to THF freeze-substituted tissues. Elemental distribution maps of leaves showed that Ni was preferentially localised in the adaxial epidermal tissues and leaf margin, with concentration of 10,000 kg–1 DW in both regions. Nickel concentrations in stem tissues obtained by µ-PIXE analysis were lower than in the leaf tissues (1,800 mg kg–1 vs. 7,800 mg kg–1 DW, respectively), and there was no clear pattern of compartmentalisation across different anatomical regions. It is possible that storage of accumulated Ni in epidermal tissues may provide Ni tolerance to this species, and may further act as a deterrent against herbivory and pathogenic attack. In H. floribundus subsp. floribundus seeds, µ-PIXE analysis did not resolve a clear pattern of Ni compartmentalisation and suggests that Ni was able to move apoplastically within the seed tissues. The role of organic acids and free amino acids (low molecular weight ligands [LMW]) in Ni detoxification in H. floribundus subsp. floribundus were quantified using high performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC). Nickel accumulation stimulated a significant increase in citric acid concentration in leaf extracts, and based on the molar ratios of Ni to citric acid (1.3:1–1.7:1), citric acid was sufficient to account for approximately 50% of the accumulated Ni. Glutamine, alanine and aspartic acid concentrations were also stimulated in response to Ni hyperaccumulation and accounted for up to 75% of the total free amino acid concentration in leaf extracts. Together, these LMW ligands may complex with accumulated Ni and contribute to its detoxification and storage in this hyperaccumulator species. Lastly, the hypothesis that hyperaccumulation of Ni in certain plants may act as an osmoticum under water stress (drought) was tested in context of H. floribundus subsp. floribundus. A 38% decline in water potential and a 68% decline in osmotic potential occurred between water stressed and unstressed plants, however, this was not matched by an increase in accumulated Ni. The results suggested that Ni was unlikely to play a role in osmotic adjustment in this species. Drought stressed plants exhibited a low water use efficiency which might be a conservative ecophysiological strategy enabling survival of this species in competitive water-limited environments.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

50

Kachenko, Anthony. „Ecophysiology and phytoremediation potential of heavy metal(Loid) accumulating plants“. University of Sydney, 2008. http://hdl.handle.net/2123/6348.

Der volle Inhalt der Quelle

Annotation:

Doctor of Philosophy(PhD)
Soil contamination with heavy metal(loid)s is a major environmental problem that requires effective and affordable remediation technologies. The utilisation of plants to remediate heavy metal(loid)s contaminated soils has attracted considerable interest as a low cost green remediation technology. The process is referred to as phytoremediation, and this versatile technology utilises plants to phytostabilise and/or phytoextract heavy metal(loid)s from contaminated soils, thereby effectively minimising their threat to ecosystem, human and animal health. Plants that can accumulate exceptionally high concentrations of heavy metal(loid)s into above-ground biomass are referred to as hyperaccumulators, and may be exploited in phytoremediation, geobotanical prospecting and/or phytomining of low-grade ore bodies. Despite the apparent tangible benefits of utilising phytoremediation techniques, a greater understanding is required to comprehend the ecophysiological aspects of species suitable for phytoremediation purposes. A screening study was instigated to assess phytoremediation potential of several fern species for soils contaminated with cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn). Hyperaccumulation was not observed in any of the studied species, and in general, species excluded heavy metal uptake by restricting their translocation into aboveground biomass. Nephrolepis cordifolia and Hypolepis muelleri were identified as possible candidates in phytostabilisation of Cu-, Pb-, Ni- or Zn-contaminated soils and Dennstaedtia davallioides appeared favourable for use in phytostabilisation of Cu- and Zn-contaminated soils. Conversely, Blechnum nudum, B. cartilagineum, Doodia aspera and Calochlaena dubia were least tolerant to most heavy metals and were classified as being least suitable for phytoremediation purposes Ensuing studies addressed the physiology of arsenic (As) hyperaccumulation in a lesser known hyperaccumulator, Pityrogramma calomelanos var. austroamericana. The phytoremediation potential of this species was compared with that of the well known As hyperaccumulator Pteris vittata. Arsenic concentration of 3,008 mg kg–1 dry weight (DW) occurred in P. calomelanos var. austroamericana fronds when exposed to 50 mg kg–1 As without visual symptoms of phytotoxicities. Conversely, P. vittata was able to hyperaccumulate 10,753 mg As kg–1 DW when exposed to 100 mg kg–1 As without the onset of phytotoxicities. In P. calomelanos var. austroamericana, As was readily translocated to fronds with concentrations 75 times greater in fronds than in roots. This species has the potential for use in phytoremediation of soils with As levels up to 50 mg kg–1. Localisation and spatial distribution of As in P. calomelanos var. austroamericana pinnule and stipe tissues was investigated using micro-proton induced X-ray emission spectrometry (µ-PIXE). Freeze-drying and freeze-substitution protocols (using tetrahydrofuran [THF] as a freeze-substitution medium) were compared to ascertain their usefulness in tissue preservation. Micro-PIXE results indicated that pinnule sections prepared by freeze-drying adequately preserved the spatial elemental distribution and tissue structure of pinnule samples. In pinnules, µ-PIXE results indicated higher As concentration than in stipe tissues, with concentrations of 3,700 and 1,600 mg As kg–1 DW, respectively. In pinnules, a clear pattern of cellular localisation was not resolved whereas vascular bundles in stipe tissues contained the highest As concentration (2,000 mg As kg–1 DW). Building on these µ-PIXE results, the chemical speciation of As in P. calomelanos var. austroamericana was determined using micro-focused X-ray fluorescence (µ-XRF) spectroscopy in conjunction with micro-focused X-ray absorption near edge structure (µ-XANES) spectroscopy. The results suggested that arsenate (AsV) absorbed by roots was reduced to arsenite (AsIII) in roots prior to transport through vascular tissues as AsV and AsIII. In pinnules, AsIII was the predominant species, presumably as aqueous-oxygen coordinated compounds. Linear least-squares combination fits of µ-XANES spectra showed AsIII as the predominant component in all tissues sampled. The results also revealed that sulphur containing thiolates may, in part sequester accumulated As. The final aspect of this thesis examined several ecophysiological strategies of Ni hyperaccumulation in Hybanthus floribundus subsp. floribundus, a native Australian perennial shrub species and promising candidate in phytoremediation of Ni-contaminated soils. Micro-PIXE analysis revealed that cellular structure in leaf tissues prepared by freeze-drying was adequately preserved as compared to THF freeze-substituted tissues. Elemental distribution maps of leaves showed that Ni was preferentially localised in the adaxial epidermal tissues and leaf margin, with concentration of 10,000 kg–1 DW in both regions. Nickel concentrations in stem tissues obtained by µ-PIXE analysis were lower than in the leaf tissues (1,800 mg kg–1 vs. 7,800 mg kg–1 DW, respectively), and there was no clear pattern of compartmentalisation across different anatomical regions. It is possible that storage of accumulated Ni in epidermal tissues may provide Ni tolerance to this species, and may further act as a deterrent against herbivory and pathogenic attack. In H. floribundus subsp. floribundus seeds, µ-PIXE analysis did not resolve a clear pattern of Ni compartmentalisation and suggests that Ni was able to move apoplastically within the seed tissues. The role of organic acids and free amino acids (low molecular weight ligands [LMW]) in Ni detoxification in H. floribundus subsp. floribundus were quantified using high performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC). Nickel accumulation stimulated a significant increase in citric acid concentration in leaf extracts, and based on the molar ratios of Ni to citric acid (1.3:1–1.7:1), citric acid was sufficient to account for approximately 50% of the accumulated Ni. Glutamine, alanine and aspartic acid concentrations were also stimulated in response to Ni hyperaccumulation and accounted for up to 75% of the total free amino acid concentration in leaf extracts. Together, these LMW ligands may complex with accumulated Ni and contribute to its detoxification and storage in this hyperaccumulator species. Lastly, the hypothesis that hyperaccumulation of Ni in certain plants may act as an osmoticum under water stress (drought) was tested in context of H. floribundus subsp. floribundus. A 38% decline in water potential and a 68% decline in osmotic potential occurred between water stressed and unstressed plants, however, this was not matched by an increase in accumulated Ni. The results suggested that Ni was unlikely to play a role in osmotic adjustment in this species. Drought stressed plants exhibited a low water use efficiency which might be a conservative ecophysiological strategy enabling survival of this species in competitive water-limited environments.

APA, Harvard, Vancouver, ISO und andere Zitierweisen

Dissertationen zum Thema „Metal tolerant“

Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an