To see the other types of publications on this topic, follow the link: Stress response of bacteria.
Dissertations / Theses on the topic 'Stress response of bacteria'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Stress response of bacteria.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Drury, Elliott C. "Stress response and hypothetical genes in Desulfovibrio vulgaris Hildenborough." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5719.
Full textAbstract:
Thesis (M.S.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. "December 2008" Includes bibliographical references.
2
Alexandre, Ana, and Solange Oliveira. "Heat shock response in bacteria with large genomes: lessons from rhizobia." Bachelor's thesis, Wiley-Blackwell Publishers, 2016. http://hdl.handle.net/10174/19210.
Full textAbstract:
Rhizobia are important soil bacteria due to their ability to establish nitrogen-fixing symbioses with legume plants. In this dual lifestyle, as free-living bacteria or as plant symbiont, rhizobia are often exposed to different environmental stresses. The present chapter overviews the current knowledge on the heat shock response of rhizobia, highlighting how these large genome bacteria respond to heat from a transcriptional point of view.
Response to heat shock in rhizobia involves genome wide changes in the transcriptome that may affect more than 30% of the genome and involve all replicons. In addition to the expected upregulation of genes already known to be involved in stress response (dnaK, groEL, ibpA, clpB), the reports on the heat shock response in rhizobia also showed particular aspects of stress response in these resourceful bacteria. The transcriptional response to heat in rhizobia includes the overexpression of a large number of genes involved in transcription and carbohydrate transport and metabolism. Additional studies are needed in order to better understand the transcriptional regulation of stress response in bacteria with large genomes.
3
Atkinson, Deborah Jane. "Stress response and inorganic poly-phosphate in the Bacillus group bacteria." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538113.
Full textAbstract:
This thesis concentrates on the Bacillus cereus group of organisms and interactions that they may encounter in their natural environment. Inorganic polyphosphate has been identified as an important factor of stress and survival in B. cereus. One of the aims of this project was to create knock out mutants of certain enzymes involved in polyphosphate metabolism in B. anthracis, the etiological agent of anthrax. Unfortunately, even though B. anthracis is very closely related to B. cereus and despite the application of published methods it was not possible to create these B. anthracis knockout mutants. In order to address the importance of inorganic polyphosphate in B. anthracis, a real time RT‐PCR assay was developed to monitor the mRNA levels of these enzymes when the bacterium is faced with harsh nutrient environments Real time RT‐PCR analysis showed that mRNA levels of the metabolizing enzymes were upregulated in low nutrient conditions but that the profiles of gene expression were varied when grown in a chemically defined media. In addition to abiotic stresses such as low nutrients, B. anthracis is also likely to face biotic stress such as predation by amoeba in the soil. Investigations were performed into the outcome of the interaction of B. cereus group bacteria with a model amoeba, Acanthamoeba polyphaga. Amoebae are bacterial predators but can also be utilised as hosts by bacterial symbionts and pathogens, such as Legionella pneumophila. It was theorised that amoebae may provide a host environment similar to that of the professional macrophages, which B. anthracis encounters in mammalian infection. These investigations confirmed that the B. cereus group bacteria demonstrate a range of interactions with amoeba cells, from surface attachment through to intracellular persistence. These studies went on to show that B. cereus, B. thuringiensis and B. anthracis can all be engulfed by amoebae when challenged in their vegetative form and that spores were able to survive, and apparently germinate. Finally these studies have identified a new developmental stage of the B. cereus group bacteria. When grown in static conditions, especially in the presence of amoeba, the bacterial cells cease to septate and large (often motile) continuous hyphae like filaments form. These filaments can be seen to “weave” together to form large “rope” like macrofibre structures which can even become visible by eye. Previously this macrofibre growth has also been seen in B. subtilis, suggesting it may be common to the whole genus. In the light of these findings we speculate that this group of pathogens have evolved complex behaviours to interact with soil amoeba in order to facilitate survival in harsh environmental conditions.
4
Perry, Leslie M. "Regulation of Alternative Sigma Factors During Oxidative and Ph Stresses in the Phototroph Rhodopseudomonas Palustris." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700009/.
Full textAbstract:
Rhodopseudomonas palustris is a metabolically versatile phototrophic α-proteobacterium. The organism experiences a wide range of stresses in its environment and during metabolism. The oxidative an pH stresses of four ECF (extracytoplasmic function) σ-factors are investigated. Three of these, σ0550, σ1813, and σ1819 show responses to light-generated singlet oxygen and respiration-generated superoxide reactive oxygen species (ROS). The EcfG homolog, σ4225, shows a high response to superoxide and acid stress. Two proteins, one containing the EcfG regulatory sequence, and an alternative exported catalase, KatE, are presented to be regulated by σ4225. Transcripts of both genes show similar responses to oxidative stress compared to σ4225, indicating it is the EcfG-like σ-factor homolog and controls the global stress response in R. palustris.
5
Zaklikowski, Anna Emilia. "The Effect of Chlorine and Chloramines on the Viability and Activity of Nitrifying Bacteria." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/33758.
Full textAbstract:
Nitrification is a significant concern for drinking water systems employing chloramines for secondary disinfection. Utilities have implemented a range of disinfection strategies that have varying levels of effectiveness in the prevention and control of nitrification events, including optimizing the chlorine-to-ammonia ratio, maintaining chloramine residual throughout the distribution system, controlling pH, and temporal switching to free chlorination. Annual or semi-annual application of free chlorination is practiced by 23% of chloraminating systems on a temporary basis as a preventative measure, even though it has the undesirable consequences of temporarily increasing disinfection byproducts, facilitating coliform detachment, and altering water taste and odor.
Although temporal free chlorination and other nitrification control methods have been widely studied in the field and in pilot-scale systems, very little is known about the stress responses of nitrifying bacteria to different disinfection strategies and the role physiological state plays in the resistance to disinfection. It is well known that many commonly studied bacteria, such as Escherichia coli, are able to better resist disinfection by free chlorine and chloramines under nutrient limitation through regulation of stress response genes that encode for DNA protection and enzymes that mediate reactive oxygen species. We compared the genomes of E. coli and the ammonia-oxidizing bacterium Nitrosomonas europaea, and found that many of the known stress response mechanisms and genes present in E. coli are absent in N. europaea or not controlled by the same mechanisms specific to bacterial growth state. These genetic differences present a general susceptibility of N. europaea to disinfection by chlorine compounds.
Using an experimental approach, we tested the hypothesis that N. europaea does not develop increased resistance to free chlorine and monochloramine during starvation to the same degree as E. coli. In addition, N. europaea cells were challenged with sequential treatments of monochloramine and hypochlorous acid to mimic the disinfectant switch employed by drinking water utilities. Indicators of activity (specific nitrite generation rate) and viability (LIVE/DEAD® BacLight⠢ membrane-integrity based assay) were measured to determine short-term effectiveness of disinfection and recovery of cells over a twelve day monitoring period. The results of disinfectant challenge experiments reinforce the hypothesis, indicating that the response of N. europaea to either disinfectant does not significantly change during the transition from exponential phase to stationary phase. Exponentially growing N. europaea cells showed greater susceptibility to hypochlorous acid and monochloramine than stationary phase E. coli cells, but had increased resistance compared with exponential phase E. coli cells. Following incubation with monochloramine, N. europaea showed increased sensitivity to subsequent treatment with hypochlorous acid. Complete loss of ammonia-oxidation activity was observed in cells immediately following treatment with hypochlorous acid, monochloramine, or a combination of both disinfectants. Replenishing ammonia and nutrients did not invoke recovery of cells, as detected in activity measurements during the twelve day monitoring period. The results provide evidence for the effectiveness of both free chlorine and chloramines in the inhibition of growth and ammonia-oxidation activity in N. europaea. Furthermore, comparison of viability and activity measurements suggest that the membrane integrity-based stain does not serve as a good indicator of activity. These insights into the responses of pure culture nitrifying bacteria to free chlorine and monochloramine could prove useful in designing disinfection strategies effective in the control of nitrification.
Master of Science
6
Drews, Oliver. "Differential proteome analysis of selected lactic acid bacteria, stress response and database construction." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974284742.
Full text
7
Mirhabibollahi, B. "Influence of mode of DNA replication on the response of Salmonella typhimurium to physical stress." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383460.
Full text
8
Zhu, Zeyu. "Multi-Omics Stress Responses and Adaptive Evolution in Pathogenic Bacteria: From Characterization Towards Diagnostic Prediction." Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:108912.
Full textAbstract:
Thesis advisor: Tim van OpijnenThesis advisor: Welkin Johnson
Pathogenic bacteria can experience various stress factors during an infection including antibiotics and the host immune system. Whether a pathogen will establish an infection largely depends on its survival-success while enduring these stress factors. We reasoned that the ability to predict whether a pathogen will survive under and/or adapt to a stressful condition will provide great diagnostic and prognostic value. However, it is unknown what information is needed to enable such predictions. We hypothesized that under a stressful condition, a bacterium triggers responses that indicate how the stress is experienced in the genome, thereby correctly identifying a stress response holds the key to enabling such predictions. Bacterial stress responses have long been studied by determining how small groups of individual genes or pathways respond to certain environmental triggers. However, the conservation of these genes and the manner in which they respond to a stress can vary widely across species. Thus, this thesis sought to achieve a genome-wide and systems-level understanding of a bacterial stress response with the goal to identify signatures that enable predictions of survival and adaptation outcomes in a pathogen- and stress-independent manner. Here, we first set up a multi-omics framework that maps out a stress response on a genome-wide level using the human respiratory pathogen Streptococcus pneumoniae as a model organism. Under an environmental stress, gene fitness changes are determined by transposon insertion sequencing (Tn-Seq) which represents the phenotypic response. Differential expression is profiled by RNA-Seq which represents as the transcriptional response. Much to our surprise, the phenotypic response and transcriptional response are separated on different genes, meaning that differentially expressed genes are poor indicators of genes that contribute to the fitness of the bacterium. By devising and performing topological network analysis, we show that phenotypic and transcriptional responses are coordinated under evolutionary familiar stress, such as nutrient depletion and host infection, in both Gram-positive and -negative pathogens. However, such coordination is lost under the relatively unfamiliar stress of antibiotic treatment. We reasoned that this could mean that a generalizable stress response signature might exist that indicates the level to which a bacterium is adapted to a stress. By extending stress response profiling to 9 antibiotics and 3 nutrient depletion conditions, we found that such a signature indeed exists and can be captured by the level of transcriptomic disruption, defined by us as transcriptomic entropy. Centered on entropy, we constructed predictive models that perform with high accuracy for both survival outcomes and antibiotic sensitivity across 7 species. To further develop these models with the goal to eventually enable predictions on disease progression, we developed a dual RNA-Seq technique that maps out the transcriptomic responses of both S. pneumoniae and its murine host during lung infection. Preliminary data show that a high entropy is observed in the pathogen’s transcriptome during clearance (a failed infection) compared to a successful/severe infection, while the host transcriptome exhibits a pro-inflammatory and active immune response under the severe infection. Lastly, we characterized evolutionary trajectories that lead to long-term survival success of S. pneumoniae, for instance this means that the bacterium successfully adapts to the presence of an antibiotic and becomes resistant or can grow successfully in the absence of a formerly critical nutrient. These trajectories show that adaptive mutations tend to occur in genes closely related to the adapted stress. Additionally, independent of the stress, adaptation triggers rewiring of transcriptional responses resulting in a change in entropy from high to low. Most importantly, we demonstrate that by combining multi-omics profiles with additional genomic data including gene conservation and expression plasticity, and feeding this into machine learning models, that adaptive evolution can become (at least partially) predictable. Additionally, the genetic diversity in bacterial genomes across different strains and species can indeed influence a bacterium’s adaptation trajectory. In conclusion, this thesis presents a substantial collection of multi-omics stress response profiles of S. pneumoniae and other pathogenic bacteria under various environmental and clinically-relevant stresses. By demonstrating the feasibility of predictions on bacterial survival and adaptive outcomes, this thesis paves the way towards future improvements on infectious disease prognostics and forecasting the emergence of antibiotic resistance
Thesis (PhD) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
9
Hardwick, Steven. "Structural and functional characterisation of partner switching proteins involved in the environmental stress response of gram-positive bacteria." Thesis, University of Newcastle Upon Tyne, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438402.
Full text
10
Reiske, Lena [Verfasser], and Volker [Akademischer Betreuer] Stefanski. "Stress hormone-induced immunomodulation and interplay between immune cells and bacteria in response to stress hormones in domestic pigs / Lena Reiske ; Betreuer: Volker Stefanski." Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2020. http://d-nb.info/1223023249/34.
Full text
11
Schmid, Amy K. "Characterization of stress response in the radioresistant bacterium Deinococcus radiodurans /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5005.
Full text
12
Reuter, Mark Andrew. "Intramolecular and intermolecular signal transduction within bacterial two component systems." Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390647.
Full text
13
Aston, John. "Response to osmotic stress by the haloalkaliphilic bacterium Halomonas campisalis." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Thesis/Spring2006/j%5Faston%5F031406.pdf.
Full text
14
Bui, Khanh Chi [Verfasser]. "Regulatory mechanisms of the disulfide stress response and the role of the bacillithiol redox buffer in Gram-positive bacteria / Khanh Chi Bui." Greifswald : Universitätsbibliothek Greifswald, 2013. http://d-nb.info/1034306782/34.
Full text
15
[Verfasser], Khanh Chi Bui. "Regulatory mechanisms of the disulfide stress response and the role of the bacillithiol redox buffer in Gram-positive bacteria / Khanh Chi Bui." Greifswald : Universitätsbibliothek Greifswald, 2013. http://d-nb.info/1034306782/34.
Full text
16
Miléřová, Miluše. "Studium odolnosti bakterií vůči vybraným stresovým faktorům." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-240552.
Full textAbstract:
The aim of the master thesis was to study the effect of the accumulation of polyhydroxyalkanoates (PHA) for bacterial resistance to selected stress factors. In the theoretical part the selected stress factors, polyhydroxyalkanoates and the involvement of polyhydroxyalkanoates into stress response of bacteria were reviewed. In the experimental part we used bacteria Cupriavidus necator H16 and its mutant strain Cupriavidus necator H16/PHB-4 unable of polyhydroxybutyrate (PHB) accumulation. The resistance of above-mentioned bacterial strains against thermal and osmotic stress was tested. According to the results of the experiment, when the bacteria were exposed to three different concentrations of NaCl (50, 100 and 200 g/l) PHB accumulating strain showed a higer resistance to hyperosmotic stress than the strain unable of PHB accumulation. There was demonstrated with Raman spectroscopy that in the hyperosmotic environment induced crystallization of the intracellular PHB granules. Transmission electron microscopy indicated that strain Cupriavidus necator H16/PHB-4 is subject to plasmolysis during hyperosmotic stress. As a consequence the hyperosmomotic stress occurs to the aggregation intracellular PHB granules in strain Cupriavidus necator H16 but there is no plasmolysis or is much less intensive.
17
Zahid, Nageena [Verfasser]. "Osmotic stress response in the industrially important bacterium Gluconobacter oxydans / Nageena Zahid." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1130704564/34.
Full text
18
Linares, Katherine Anne. "Evaluating strategies for integrating bacterial cells into a biosensor designed to detect electrophilic toxins." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/10113.
Full textAbstract:
To improve the process stability of wastewater treatment plants, the construction of a whole-cell bacterial biosensor is explored to harness the natural stress response of the bacterial cells. The stress response selected in this work is the glutathione-gated potassium efflux (GGKE) system, which responds to electrophilic stress by effluxing potassium from the interior to the exterior of the cell. Thus, the bulk potassium in solution can be monitored as an indicator of bacterial stress. By utilizing this stress response in a biosensor, the efflux of potassium can be correlated to the stress response of the immobilized culture, providing an early warning system for electrophilic shock. This type of shock is a causative factor in many process upset events in wastewater treatment plants, so the application of the sensor would be an early warning device for such plants.
The research conducted here focused on the biological element of the biosensor under development. Three immobilization matrices were explored to determine the cell viability and potassium efflux potential from immobilized cells: a calcium alginate, a photopolymer, and a thermally reversible gel. The calcium alginate was unstable, and dissolved after five days, such that the long-term impact of immobilization on the cells could not be determined in the matrix. The photopolymer resulted in very low actvity and viability of immobilized cellsOf the three matrices tested, indicating that the composition of the polymer was toxic to the cells. Of the matrices tested, the thermally-reversible gel showed the best response for further study, in that the matrix did not inhibit cell activity or potassium efflux.Master of Science
19
Båth, Klara. "Factors important for persistence of Lactobacillus reuteri in the gastrointestinal tract : a study of extracellular proteins, stress response and survival of mutants in a model system /." Uppsala : Department of Microbiology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200722.pdf.
Full text
20
Furman, Ran. "DksA Beyond the Stringent Response: Investigating the Functions of a Diverse Bacterial Transcription Factor." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367584519.
Full text
21
Landgraf, Dirk. "Quantifying Localizations and Dynamics in Single Bacterial Cells." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10612.
Full textAbstract:
Levels of macromolecules fluctuate both spatially and temporally in individual cells. Such heterogeneity could be exploited for bet hedging in uncertain environments, or be suppressed by negative feedback if perturbations are deleterious. For the master stress-response regulator in Escherichia coli, RpoS, both of these scenarios have been suggested. RpoS levels are also exceedingly low and controlled by the ClpXP protease, which reportedly displays extreme spatial heterogeneity. However, little is known quantitatively about RpoS dynamics. This is partly because no functional protein fusions exist, but also because the quantitative tools for studying fluctuations and localizations are limited, particularly ones that can be independently validated. Here I develop such methods and begin applying them to RpoS. Protein localization measurements increasingly rely on fluorescent protein fusions and are difficult to verify independently. I designed a non-intrusive method for validating localization patterns in live bacterial cells by exploiting post-division heterogeneity in downstream processes. Applying this assay to the ClpXP protease, widely reported to form biologically relevant foci, revealed in fact that the protease molecules are not specifically localized inside cells, as confirmed by four independent methods. I further evaluated 20+ commonly used fluorescent reporters and found that many cause severe mislocalization when fused to homo-oligomers, likely due to avidity effects. Further reinvestigating other foci-forming proteins strongly suggests that the previously reported foci were all caused by the fluorescent proteins used. For mRNAs – which are often present in low numbers per cell and major sources of non-genetic heterogeneity – existing single-cell assays have unknown accuracy: the experimental counting errors could completely over-shadow the natural variation. I therefore optimized and cross-evaluated two single-molecule mRNA detection methods. Several problems were identified and solutions discussed. I succeeded in building a functional RpoS protein fusion, and used bulk methods to show that the RpoS feedback loop is effectively not operating during exponential- phase growth. Mathematical analyses and initial experiments in a microfluidic device further suggest that the RpoS system has several unusual properties contributing towards extremely fast stress response. A stochastic analysis further suggests that the RpoS feedback loop cannot suppress spontaneous fluctuations, and preliminary experiments indicate that large deviations might indeed play important roles.
22
Obruča, Stanislav. "Regulovaná produkce a biodegradace vybraných typů biomateriálů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2010. http://www.nusl.cz/ntk/nusl-233306.
Full textAbstract:
Předložená disertační práce se zabývá studiem produkce a degradace polymerních materiálů s využitím mikroorganismů. Hlavní pozornost je upřena ke studiu produkce polyesterů bakteriálního původu - polyhydroxyalkanoátů. Tyto materiály jsou akumulovány celou řadou bakterií jako zásobní zdroj uhlíku, energie a redukční síly. Díky svým mechanickým vlastnostem, kterými silně připomínají tradiční syntetické polymery jako jsou polyetylén nebo polypropylén, a také díky své snadné odbouratelnosti v přírodním prostředí, jsou polyhydroxyalkanoáty považovány za ekologickou alternativu k tradičním plastům vyráběným z ropy. Polyhydroxyalkanoáty mají potenciál najít řadu aplikací v průmyslu, zemědělství ale také v medicíně. Významná část předložené práce je zaměřena na produkci polyhydroxyalkanoátů z odpadních substrátů pocházejících především z potravinářských výrob. Testována byla odpadní syrovátka nebo odpadní oleje z různých zdrojů. Právě využití levných odpadních substrátů je strategií, která by mohla přispět ke snížení ceny polyhydroxyalkanoátů a tím usnadnit jejich masové rozšíření. Podle výsledků dosažených v této práci jsou právě odpadní olejové substráty velice perspektivní cestou k ekonomicky rentabilní biotechnologické produkci polyhydroxyalkanoátů. Další část předložené práce se zabývá studiu spojení metabolické role polyhydroxyalkanoátů a stresové odpovědi bakterií. V této práci bylo zjištěno, že expozice bakteriální kultury řízené dávce etanolu nebo peroxidu vodíku významně navýší dosažené výtěžky a to o přibližně 30 %. Po aplikaci výše zmíněných stresových faktorů došlo k aktivaci metabolických drah vedoucí k odbourání stresového faktoru z média. Výsledkem bylo navýšení poměru NAD(P)H/NAD(P)+, což vedlo k částečné inhibici Krebsova cyklu a naopak aktivaci biosyntetické dráhy polyhydroxyalkanoátů. Mimoto došlo k významnému navýšení molekulové hmotnosti výsledných materiálů. Podle těchto výsledků se regulovaná aplikace vhodně zvolených stresových podmínek zdá být zajímavou strategií, která vede nejen k navýšení celkových výtěžků, ale také významnému zlepšení vlastností polymeru. Poslední část disertační práce se zabývala studiem procesu biodegradace polyuretanových materiálů. Polyuretanové eleastomery byly modifikovány rozličnými biopolymery za účelem navýšení jejich biodegradability. Tyto materiály byly posléze vystaveny působení směsné termofilní kultury jako modelového systému, který simuluje přirozené konsorcium bakterií. Přítomnost testovaných materiálů v kultivačním médiu vedla k neobvyklým růstovým charakteristikám bakteriální kultury. V průběhu prvních několika dní byl růst kultury silně inhibován, nicméně po překonání této neobvykle dlouhé lag-fáze došlo k intenzivnímu nárůstu kultury. Hlavní podíl na hmotnostním úbytku testovaných materiálů během experimentů měl samovolný rozpad materiálů, nicméně byl pozorován i vliv bakteriální kultury, kdy míra biotické degradace závisela na použitém modifikačním činidle. Nejvyšší míra biotické degradace byla pozorována u polyuretanového materiálu modifikovaného acetylovanou celulózou. Lag-fáze byla způsobena uvolněním nezreagovaného katalyzátoru (dibutylcínlaurát) a polyolu do kultivačního média. Bakteriální kultura se však po čase dokázala na přítomnost toxických látek v médiu adaptovat nebo je dokázala eliminovat.
23
Wen, Yi. "Inhibitory effects of U(VI) on bacterial metabolism and transcriptional response of Shewanella oneidensis MR-1 to uranium stress /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
24
Guo, Lijun [Verfasser], and Marc [Akademischer Betreuer] Bramkamp. "Role of a bacterial dynamin-like protein DynA in resistance to environmental stress response / Lijun Guo ; Betreuer: Marc Bramkamp." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2021. http://d-nb.info/1238016987/34.
Full text
25
Surujon, Defne. "Computational approaches in infectious disease research: Towards improved diagnostic methods." Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:109089.
Full textAbstract:
Thesis advisor: Kenneth WilliamsDue to overuse and misuse of antibiotics, the global threat of antibiotic resistance is a growing crisis. Three critical issues surrounding antibiotic resistance are the lack of rapid testing, treatment failure, and evolution of resistance. However, with new technology facilitating data collection and powerful statistical learning advances, our understanding of the bacterial stress response to antibiotics is rapidly expanding. With a recent influx of omics data, it has become possible to develop powerful computational methods that make the best use of growing systems-level datasets. In this work, I present several such approaches that address the three challenges around resistance. While this body of work was motivated by the antibiotic resistance crisis, the approaches presented here favor generalization, that is, applicability beyond just one context. First, I present ShinyOmics, a web-based application that allow visualization, sharing, exploration and comparison of systems-level data. An overview of transcriptomics data in the bacterial pathogen Streptococcus pneumoniae led to the hypothesis that stress-susceptible strains have more chaotic gene expression patterns than stress-resistant ones. This hypothesis was supported by data from multiple strains, species, antibiotics and non-antibiotic stress factors, leading to the development of a transcriptomic entropy based, general predictor for bacterial fitness. I show the potential utility of this predictor in predicting antibiotic susceptibility phenotype, and drug minimum inhibitory concentrations, which can be applied to bacterial isolates from patients in the near future. Predictors for antibiotic susceptibility are of great value when there is large phenotypic variability across isolates from the same species. Phenotypic variability is accompanied by genomic diversity harbored within a species. I address the genomic diversity by developing BFClust, a software package that for the first time enables pan-genome analysis with confidence scores. Using pan-genome level information, I then develop predictors of essential genes unique to certain strains and predictors for genes that acquire adaptive mutations under prolonged stress exposure. Genes that are essential offer attractive drug targets, and those that are essential only in certain strains would make great targets for very narrow-spectrum antibiotics, potentially leading the way to personalized therapies in infectious disease. Finally, the prediction of adaptive outcome can lead to predictions of future cross-resistance or collateral sensitivities. Overall, this body of work exemplifies how computational methods can complement the increasingly rapid data generation in the lab, and pave the way to the development of more effective antibiotic stewardship practices
Thesis (PhD) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
26
Timoner, Amer Xisca. "Stream biofilm responses to flow intermittency." Doctoral thesis, Universitat de Girona, 2014. http://hdl.handle.net/10803/283569.
Full textAbstract:
Streams experiencing a recurrent non-flow phase (i.e., flow intermittency) are characteristic of world regions with arid and semi-arid climates, where Mediterranean regions are part of. During non-flow streambed sediments, and consequently, microorganisms inhabiting these sediments are exposed to desiccation. These microorganisms, assembled in biofilms, lead a substantial part of the ecosystem processes. They recycle the carbon materials, intervene in the nutrient cycles and are on the base of the food web, fueling energy to the higher trophic levels. The aim of this tesis is to understand how biofilms respond to flow intermittency in order to unravel the consequences of the increasing spatial and temporal extent of flow intermittency, as a consequence of the global change, on the biogeochemical cycles and on the ecosystem functions in temporary streams. Structural and functional biofilm responses were analyzed at the cellular level (algae and bacteria), as well as at the whole biofilm responses (autotrophic vs heterotrophic processes) in two different field studiesEls rius que experimenten una fase sense cabal (intermitència fluvial) són característics de les regions del món amb climes àrids i semi-àrids, com ara les regions de la Mediterrànies. Durant la fase seca es produeix la dessecació de la llera del riu i conseqüentment els microorganismes que creixen sobre aquests sediments estan exposats a la dessecació. El conjunt d’aquests microorganismes es coneix com a biofilm, el qual juga un paper clau en el processament de la matèria orgànica i en els cicles del carboni i nutrients, A més són a la base de la xarxa tròfica aportant energia als nivells tròfics superiors. L'objectiu principal d'aquesta tesi és entendre el funcionament del biofilm quan es dona la fase seca, pas clau per entendre i predir les implicacions que tenen els períodes creixents sense cabal en els cicles biogeoquímics i en el funcionament de l’ecosistema. Les respostes estructurals i funcionals del biofilm des d’un punt de vista cel·lular (algues i bacteris), així com també en el conjunt del biofilm (processos autotròfics i heterotròfics) es van investigar mitjançant dos estudis de camp
27
Baudier, Claire. "How do the metabolites, GTP and (p)ppGpp, simultaneously control the occurrence of translational errors and resource allocation in bacteria?" Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS202.
Full textAbstract:
Bien que divers mécanismes coopèrent pour empêcher les erreurs lors de la synthèse des protéines chez les bactéries, des erreurs traductionnelles de type « frameshift » (ETFs) ou « faux-sens » peuvent avoir lieu. En particulier, les ETFs ont été détectées à de faibles niveaux lors de la phase de croissance exponentielle et à des niveaux plus élevés durant la phase de croissance stationnaire chez Escherichia coli et Bacillus subtilis. Ces observations ont conduit les chercheurs à revoir le rôle de la "réponse stringente" dans la survenue des ETFs, qui constitue l’un des mécanismes clé de l'adaptation bactérienne aux changements nutritionnels. Elle découle de l'interaction entre un ribosome en cours de traduction et la protéines RelA/SpoT ce qui permet de détecter les ARNs de transfert (ARNts) non chargés et résulte en la production d'une molécule appelée (p)ppGpp . Dans une souche mutante relA incapable de synthétiser le (p)ppGpp, les ETFs sont fortement augmentées.Dans ce contexte, notre objectif principal a été de revisiter le rôle de la réponse stringente dans le contrôle des erreurs traductionnelles et de clarifier le rôle des deux métabolites antagonistes GTP et (p)ppGpp. Par exemple, le GTP stimule l'initiation de la traduction (en ciblant le facteur d'initiation IF2) alors que le (p)ppGpp inhibe l'initiation de la traduction (en rentrant en concurrence avec le GTP pour se fixer sur IF2).A cette fin, nous avons utilisé le modèle des bactéries à Gram positif B. subtilis, conçu trois systèmes rapporteurs distincts pour détecter les ETFs et construit une souche incapable de synthétiser du (p)ppGpp (appelée "(p)ppGpp0"). Nous avons observé qu'au cours de la croissance dans des milieux pauvres, les ETFs augmentent en l'absence de (p)ppGpp durant la phase exponentielle et que, contrairement à la souche sauvage, la souche (p)ppGpp0 présente un pic d’ETFs en milieu riche pendant la transition à la phase stationnaire. En contrôlant les niveaux intracellulaires de GTP dans la souche (p)ppGpp0, nous avons montré que l'abondance de GTP est le facteur qui déclenche l'apparition des ETFs. Néanmoins, après une "faible" induction de la biosynthèse du GTP conduisant à des taux de croissance sous-optimaux, le niveau d’ETFs forme toujours un pic lors de la transition vers la phase stationnaire, ce qui montre que le mode d'action du (p)ppGpp pour prévenir l'apparition des ETFs ne repose pas uniquement sur son action inhibitrice de la biosynthèse du GTP. Nous nous sommes alors concentrés sur l'effet inhibiteur du (p)ppGpp sur IF2 et avons mimé son action en injectant des drogues connues pour inhiber l'initiation de la traduction. Nous avons ainsi démontré qu'en réduisant l'initiation de la traduction lors de l'épuisement des aminoacyl-ARNts, la souche "(p)ppGpp0" est capable de contrôler de façon optimale le taux d’ETFs lors de la transition vers la phase stationnaire.Dans une deuxième partie, nous avons étudié comment la transcription et la traduction sont affectées par les variations du niveau de GTP et de (p)ppGpp. Nous avons observé que les gènes possédant un "+1" de transcription (TSS, « transcription start site ») composé de deux guanines (gènes artificiels et ARNs ribosomaux) ont vu leur taux de transcription positivement corrélés au taux de croissance à l'inverse des gènes possédant un TSS composé de deux adénines. Cette différence est encore plus prononcée pour la souche (p)ppGpp0 cultivée en milieu riche lors de l'ajout de guanosine (ce qui conduit à un niveau élevé de GTP).En conclusion, nous avons démontré que le (p)ppGpp contrôle le niveau d'erreurs traductionnelles lors de la croissance en régime permanent en abaissant les niveaux de GTP et lors d’un changement nutritionnel en inhibant spécifiquement l'initiation de la traduction, assurant une allocation parcimonieuse des ressources au sein de la bactérieEven though diverse mechanisms cooperate to prevent protein synthesis errors in bacteria, missense and translational frameshift errors (TFEs) can occur . In particular, TFEs were detected at low levels in the exponential growth phase and at higher levels in the stationary phase in both Escherichia coli and Bacillus subtilis. This observation led researchers to revisit the role of the “stringent response” in the occurrence of TFEs since it is the key mechanism involved in the bacterial adaptation to nutritional downshifts. It relies on the interaction between the RelA/SpoT proteins and the translating ribosomes, which leads to the detection of uncharged tRNAs and to the production of an alarmone called (p)ppGpp. In a relA mutant strains unable to synthesize (p)ppGpp, translational errors are highly increased.In this context, the main goal of our work was to revisit the role of the stringent response in the translational error control and to clarify the role of the two key, antagonistic metabolites GTP and (p)ppGpp. Indeed, while GTP enhances translation initiation (targeting the initiation factor IF2) and elongation (targeting the elongation factor EF-Tu) , (p)ppGpp inhibits GTP biosynthesis (reducing the enzyme activity of Gmk, HprT and GuaB) and translation initiation (competing with GTP on IF2).For this purpose, we used the Gram positive model bacterium B. subtilis, designed three distinct reporter systems to detect TFEs and built a strain unable to synthesize (p)ppGpp (called “(p)ppGpp0”). We observed that during growth in poor media TFEs were increased in the absence of (p)ppGpp in the exponential phase (i.e. steady-state growth) and that by contrast to the wild type, the (p)ppGpp0 strain exhibited a TFE burst during the transition in rich medium to the stationary phase. By controlling intracellular levels of GTP in the (p)ppGpp0 strain, we showed that GTP abundance is the trigger factor of TFEs occurrence. Nevertheless, upon a "weak" induction of GTP biosynthesis leading to sub-optimal growth rates, the TFEs rate still peaked during the transition to the stationary phase, which demonstrated that the mode of action of (p)ppGpp to prevent TFEs occurrence did not only rely on its inhibition of GTP biosynthesis. We then focused on the (p)ppGpp inhibitory effect on IF2 and mimicked its action by injecting drugs known to inhibit translation initiation. Hence, we demonstrated that by reducing translation initiation (injecting drugs) upon aminoacyl-tRNAs depletion (p)ppgGp0 wild-strain type cells is are able to optimally control the rate of TFEs in the transition to the stationary phase. The same conclusion is obtained even in presence of a high GTP level.In a second part, we studied how transcription and translation are affected by variations in GTP and (p)ppGpp abundances. We observed that genes possessing a transcription start site (TSS) made of two guanines were more importantly transcribed at higher growth rates than genes possessing a TSS made of two adenines. This difference was even more pronounced for (p)ppGpp0 strains grown in rich medium upon guanosine addition (leading to a high level of GTP). Moreover, the ribosomal RNAs (rrns; for which the TSS is a guanine) synthesis level seemed to be positively correlated to GTP levels during exponential growth in poor and rich media as observed by the modulation of GTP biosynthesis.In conclusion, we demonstrated that (p)ppGpp controls the occurrence of translational errors during steady-state growth by decreasing GTP levels and during a nutritional downshift by specifically inhibiting translation initiation ensuring a parsimonious , which also globally affects resource allocation
28
Tu, Nhan. "Characterization of Two Novel Gene Regulatory Systems in the Zoonotic Bacterium Bartonella henselae." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/6042.
Full textAbstract:
The genus Bartonella contains Gram-negative arthropod-borne bacteria that are found in many small animal reservoirs and are capable of causing human disease. Bacteria utilize a general stress response system to combat stresses from their surrounding environments. In α-proteobacteria, the general stress response system uses an alternate σ factor as the main regulator and incorporates it with a two-component system into a unique system. Our study identifies the general stress response system in the α-proteobacterium, Bartonella henselae, where the gene synteny is conserved and both the PhyR and alternate σ factor have similar sequence and domain structures with other α-proteobacteria. Furthermore, we showed that the general stress response genes are up-regulated under conditions that mimic the cat flea vector. We also showed that both RpoE and PhyR positively regulate this system and that RpoE also affects transcription of genes encoding heme-binding proteins and the BadA adhesin. Finally, we also identified a histidine kinase, annotated as BH13820 that can potentially phosphorylate PhyR. In addition, analysis of the transcriptome from the Houston-1 strain of B. henselae by RNA-Seq reveals a family of small RNAs (termed Brt1-Brt9 for Bartonella Regulatory Transcripts 1-9) that may rapidly adapt gene expression patterns to the diverse hosts of this bacterium. This family of RNAs consists of nine novel, highly expressed intergenic transcripts, ranging from 193-205 nucleotides with a high degree of homology (70-100%) and stable predicted secondary structures that are unique to the genus Bartonella. Northern blot analysis indicates that transcription of these sRNAs was highest under conditions mimicking those of the cat flea vector (low temperature, high hemin). The predicted promoters for Brt1-Brt9 have been cloned upstream of a β-galactosidase reporter gene in pNS2 to identify conditions altering transcription. Immediately downstream of each of the nine putative sRNAs is a helix-turn-helix DNA binding protein (termed Trp1-9 for Transcriptional Regulatory Protein 1-9) that is poorly transcribed as determined by RNA-Seq. This gene organization is suggestive of a potential cis-acting RNA mechanism or riboswitch with the RNA secondary structure controlling transcription of the cognate downstream trp.
29
Jaskulski, Itiane Barcellos. "Ação in vivo de Lactococcus lactis subsp. lactis (R7) com potencial probiótico na estabilização de células cancerígenas no epitélio colorretal." Universidade Federal de Pelotas, 2018. http://guaiaca.ufpel.edu.br:8080/handle/prefix/4100.
Full textAbstract:
Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2018-07-30T18:34:11Z
No. of bitstreams: 1
Itiane Barcellos Jaskulski.pdf: 1235418 bytes, checksum: 9fdf9c1822423763aa421923556d593c (MD5)Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2018-07-31T19:15:23Z (GMT) No. of bitstreams: 1 Itiane Barcellos Jaskulski.pdf: 1235418 bytes, checksum: 9fdf9c1822423763aa421923556d593c (MD5)
Made available in DSpace on 2018-07-31T19:15:23Z (GMT). No. of bitstreams: 1 Itiane Barcellos Jaskulski.pdf: 1235418 bytes, checksum: 9fdf9c1822423763aa421923556d593c (MD5) Previous issue date: 2018-03-05
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Na última década, a ciência contribuiu significativamente para inúmeros avanços e progressos em relação ao tratamento e prevenção do câncer colorretal (CCR), porém, a prevalência global e taxa de mortalidade ainda permanecem altos. Há relatos sobre efeitos benéficos de espécies de Bifidobacterium e Lactobacillus com potencial probiótico na prevenção de CCR, no entanto, a bactéria probiótica Lactococcus lactis subps. lactis é comumente utilizada para fins industriais, não havendo comprovações in vivo sobre seu potencial anticarcinogênico. Visto o interesse emergente dos efeitos benéficos dos probióticos a fim de prevenir ou tratar o CCR, o presente estudo objetivou explorar os efeitos protetores de Lactococcus lactis subsp. lactis sobre o CCR. Ratos da linhagem Wistar receberam doses subcutâneas de 1,2 dimetilhidrazina (DMH), suspensão de Lactococcus lactis subsp. lactis por via oral e dieta hipercalórica. Após 20 semanas, os tecidos intestinais foram analisados histologicamente, além de controle ponderal e consumo de alimentos, parâmetros hematológicos e bioquímicos, estresse oxidativo e estado redox do tecido hepático. De acordo com o resultado, o isolado demonstrou potencial anticarcinogênico contra CCR, estabilizou o ganho de peso, reduziu adiposidade abdominal, apresentou ligeira melhora da resposta imune, exerceu atividade antioxidante frente ao estresse oxidativo e, demonstrou proteção à peroxidação lipídica. Estes resultados são promissores para a ciência frente às pesquisas relacionadas ao tratamento e prevenção de CCR.
In the last decade, science has contributed significantly to numerous advances and advances in treating and preventing colorectal cancer (CRC), but the overall prevalence and mortality rate remain high. There are reports on the beneficial effects of Bifidobacterium and Lactobacillus species with probiotic potential in the prevention of CRC, however, the probiotic bacterium Lactococcus lactis subps. lactis is commonly used for industrial purposes, and there is no in vivo evidence for its anticarcinogenic potential. Given the emerging interest in the beneficial effects of probiotics in preventing or treating CRC, the present study aimed to explore the protective effects of Lactococcus lactis subsp. lactis in the CRC. Wistar rats received subcutaneous doses of 1,2-dimethylhydrazine (DMH), suspension of Lactococcus lactis subsp. lactis orally and a hypercaloric diet. After 20 weeks, intestinal tissues were analyzed histologically, in addition to weight control and food consumption, hematological and biochemical parameters, oxidative stress and redox status of the hepatic tissue. According to the results, the isolate demonstrated anticarcinogenic potential against CRC, stabilized the weight gain, reduced abdominal adiposity, showed a slight improvement in the immune response, exerted antioxidant activity against oxidative stress and demonstrated protection of lipid peroxidation. These results are promising for science regarding the treatment and prevention of CRC.
30
Stevanin, Tania Maria. "Bacterial flavohaemoglobins : physiological function and responses to nitrosative stress." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340137.
Full text
31
Slaninová, Eva. "Metabolická a biofyzikální charakterizace bakteriálních buněk schopných akumulace PHA." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-438297.
Full textAbstract:
This thesis deals with the characterization of bacterial cells capable of polyhydroxyalkanoates (PHA) accumulation. The dissertation thesis is written in the form of a discussed published publications which are attached to the thesis as appendixes. The work develops a study of the current topic of the protective functions of PHA and clarifies protective mechanisms against selected stressors. Firstly, we focused on the protective effects of PHA granules against UV radiation and osmotic stress, specifically hypotonic conditions. In the case of UV exposition, the cells protected themselves by scattering UV radiation on the intracellular granules protecting especially nucleoid. When exposed to osmotic stress, the amorphous state of PHA granules is very important since it is capable of stabilization of cell membranes under hypertonic stress, afterwards, bacterial cells can maintain their integrity during the subsequent hypotonic challenge. In general, the amorphous state of PHA granules is key to ensure the proper biological functions of PHA whether as storage or protective polymer. Therefore, in the next part of this work, we focused on the core of the stabilization mechanism that protects native PHA granules from crystallization and thus the intracellular polymer maintains in a thermodynamically unfavorable amorphous phase state. Based on experimental work, we applied selected stresses because we proposed a new model of stabilization of the amorphous state of PHA granules in vivo. It consists of two mechanisms, where small volumes of PHA granules reduce the rates of crystallization and at the same time the water present in the granules plays the role of a low molecular plasticizer. Due to the metabolic apparatus of bacterial cells, PHA are simultaneously synthesized and degraded which leads to an increment of intracellular concentration of monomers that also figure in the protective effect of PHA. In this context, we aimed at the description of the mechanism of cryoprotective effects of 3-hydroxybutyrate, the monomer of the most common of PHA, poly(3-hydroxybutyrate). Hence, we constructed an equilibrium and non-equilibrium phase diagram of the 3HB-water system to prove that 3HB is a very effective cryoprotectant. This fundamental understanding of the protective properties of PHA monomers could be also used in the food industry or cryopreservation of biological samples.
32
Yang, Yifan. "Physiological constraints and evolutionary trade-offs underlying bacterial aging, caloric restriction and longevity." Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCB158/document.
Full textAbstract:
Les théories évolutives du vieillissement et la théorie du «disposable soma» en particulier ont été la base théorique d'une avance récente de recherche sur le vieillissement animal. Pourtant, leur hypothèse centrale sur la physiologie de l'entretien et de la réparation cellulaires n'a pas été testée empiriquement. Dans cette thèse, j'ai analysé la physiologie du vieillissement de Escherichia coli sous restriction de carbone, en tant que système modèle pour valider empiriquement les théories évolutives du vieillissement. Les outils microfluidiques sont utilisés pour isoler de larges populations de cellules isolées de E. coli et pour obtenir une restriction carbonée homogène. Malgré le partage de la même génétique et des conditions environnementales, les cellules individuelles de la population présentent des variations significatives de la durée de vie et de cause de décès. Les distributions de durée de vie présentent des caractéristiques typiques du processus de vieillissement, souvent observées en études démographiques animales et humaines. Le taux de vieillissement peut être modifié par des mutations de la réponse générale au stress. Comme la longévité induite par la restriction calorique, la réponse générale au stress prolonge la durée de vie d'E.coli en atténuant l'effet du vieillissement au détriment des besoins immédiats des cellules. Un modèle quantitatif de ce compromis physiologique est construit et correctement prédit des observations expérimentales. En conclusion, je confirme la théorie du «disposable soma» du vieillissement avec les détails physiologiques du vieillissement de E.coli en famineThe evolutionary theories of aging and the disposable soma theory in particular, have been the theoretical basis for a recent surge of animal aging research. Yet their central assumption about the physiology of cellular maintenance and repair has not been empirically tested. In this thesis, I analysed the physiology of E.coli aging under carbon starvation, as a model system to empirically validate evolutionary theories of aging. Microfluidic tools are used to isolate large populations of isogenic single E.coli cells, and to achieve homogenous carbon starvation. Despite sharing the same genetical background and environmental conditions, individual cells in the population exhibit significant variations in lifespans and causes of death. Distributions of lifespans exhibit typical features of the aging process, often seen in animal and human demographic studies. The rate of aging can be altered by mutations of the general stress response pathway. Resembling caloric restriction induced longevity, the general stress response pathway extends starvation lifespans of E.coli by attenuating the effect of aging at the expense of immediate needs of the cells. A quantitative model of this physiological trade-off is constructed and correctly predicted experimental observations. As a conclusion, I substantiate the disposable soma theory of aging with the physiological details of E.coli aging in starvation
33
Staron, Anna. "Phylogenetic and functional analyses of stress-responsive bacterial transmembrane signal transducing systems." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-149558.
Full text
34
Paddick, James Sinclair. "Aspects of stress on oral bacteria." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414438.
Full text
35
Bradley, Dominic. "The universal stress proteins of bacteria." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6946.
Full textAbstract:
Universal stress proteins (USPs) are a widespread and abundant protein family often linked to survival during stress. However, their exact biochemical and cellular roles are incompletely understood. Mycobacterium tuberculosis (Mtb) has 10 USPs, of which Rv1636 appears to be unique in its domain structure and being the only USP conserved in M. leprae. Over-expression of Rv1636 in M. smegmatis indicated that this protein does not share the growth arrest phenotype of another Mtb USP, Rv2623, suggesting distinct roles for the Mtb USPs. Purified Rv1636 was shown to have novel nucleotide binding capabilities when subjected to UV crosslinking. A range of site-directed mutants of Rv1636 were produced, including mutations within a predicted nucleotide binding motif, with the aim of identifying and characterising key residues within the Rv1636 protein. Further putative biochemical activities, including nucleotide triphosphatase, nucyleotidylyation and auto-phosphorylation were also investigated in vitro; however Rv1636 could not be shown to definitively possess these activities, raising the possibility that addition factors may be present in vivo. Bioinformatic analysis of Rv1636 has provided an in-depth look at the protein. The crystal structure of Rv1636 shows a strand swapped dimer conformation that appears to block the predicted nucleotide binding site, providing a possible reason for the low NTPase activity previously observed. Truncated Rv1636 constructs were successfully generated, in which the strand swapped dimer was disrupted, and subjected to biophysical analysis, including analytical ultracentrifugation and size exclusion chromatography combined with multi-angle light scattering. Previous Mtb single-USP mutants are known to have no phenotype under a range of stress conditions. For this reason the P. aeruginosa USP PA3309, which does possess a stress survival phenotype, was also investigated. This provided the opportunity to investigate the role of USPs and their putative nucleotide binding motif in vivo. Site-directed mutants of PA3309 were generated to investigate the role of the nucleotide binding motif in vivo. It remains to be determined if the survival defect observed for ΔPA3309 strain can be complemented with these mutants as the vector system used in these experiments proved unable to integrate into the attB site of the genome. Through the analysis of the USPs from mycobacteria and Pseudomonas, the aim was to elucidate a greater understanding of the role of Rv1636 in Mtb and the role of USPs in general. The bioinformatic and biochemical analyses of USPs, in addition to the site directed mutants generated as a result of this work, will provide a strong foundation for future studies.
36
Peschek, Nikolai [Verfasser], and Kai [Akademischer Betreuer] Papenfort. "Functional characterization of bacterial sRNAs involved in stress responses and quorum sensing of bacterial pathogens / Nikolai Peschek ; Betreuer: Kai Papenfort." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1216039372/34.
Full text
37
Purdon, Scott Drummond. "Starvation survival response of sulphate-reducing bacteria." Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340595.
Full textAbstract:
This thesis aims to investigate how SRB endure long periods of nutrient deprivation in the oligotrophic conditions of the North Sea. The presence of small cells in the marine environment has been extensively documented. These small cells are termed ultramicrobacteria, and are defined as being less than 0.3 μm in diameter. The formation of small cells by SRB was postulated to facilitate penetration of SRB deep within oil reservoirs, during water injection, exacerbating SRB associated problems. These studies revealed that a maximum of 15% of starving SRB populations formed UMB. Cultures starved for up to 6 years did not demonstrate an increase in UMB formation. Cell size studies revealed that SRB demonstrated a maximum 62% cell size decrease during starvation. Total cell counts revealed a constant cell number throughout starvation studies indicating a decrease in cell size by cell dwarfing. Transmission electron microscopy revealed a decrease in cellular content during starvation. This is consistent with a decrease in cell diameter during starvation. There was no difference in cell size decrease when cells were starved in the presence or absence of sulphate. There appeared, however, to be enhanced recoverability of cells starved in the presence of sulphate. SRB were demonstrated to be able to withstand simultaneous periods of sulphate and carbon starvation. This may have serious consequences for the oil industry as sulphate is often limiting in oil reservoirs. This evidence suggests that SRB could endure such conditions and recover when sulphate becomes available. SRB appear to enter a dormant phase shortly after the onset of starvation. Metabolic studies indicated that the entry into starvation was characterised by an initial increase in metabolic activity followed by a sharp decrease in metabolic activity to negligible levels. Metabolic activity could be re-initiated following inoculation into fresh growth medium.
38
Thibault, Derek M. "Applications of droplet-based microfluidics to identify genetic mechanisms behind stress responses in bacterial pathogens." Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:106985.
Full textAbstract:
Thesis advisor: Michelle MeyerThe primary bacterial targets for most antibiotics are well known. To survive the stress of an antibiotic a bacterium must decrease the antibiotic to target binding ratio to escape from harmful effects. This can occur through a number of different functions including down-regulation of the target, mutation of the binding site on the target, and decreasing the intake or increasing the efflux of the antibiotic. However, it is becoming more evident that an antibiotic stress response influences more than just the primary target, and that a wave of secondary responses can be triggered throughout the bacterium. As a result resistance mutations may arise in genes that are indirectly affected by the initial interaction between the antibiotic and target. These indirect responses have been found to be associated with metabolism, regulation, cell division, oxidative stress, and other critical pathways. One technique recently developed in our lab, called transposon insertion sequencing (Tn-seq), can be used to further understand the complexity of these indirect responses by profiling growth rates (fitness) of mutants at a genome-wide level. However, Tn-seq is normally performed with large libraries of pooled mutants and thus it remains unclear how this may influence fitness of some independent mutants that may be compensated by others in the population. Additionally, since the original method has only utilized planktonic culture, it is also not clear how higher order bacterial structures, such as biofilms or microcolonies, influence bacterial fitness. To better understand the dynamics of pooled versus individual mutant culture, as well as the effect of community structure in microcolony development on the influence of fitness, we adapted a droplet microfluidics-based technique to encapsulate and culture single mutants. We were able to successfully encapsulate at least 7 different species of bacterial pathogens, including Streptococcus pneumoniae, and culture them planktonically, or as microcolonies, in either monodisperse liquid or agarose droplets. These experiments, however, raised an important challenge: the DNA yield from one encapsulation experiment is insufficient to generate samples for sequencing by means of the traditional Tn-seq method. This led us to develop a novel Tn-seq DNA library preparation method, which is able to generate functional Tn-seq library molecules from picogram amounts of DNA. This method is not ideal yet because fitness data generated through the new method currently does not correlate well with data from traditional Tn-seq library preparation. However, we have identified one major culprit that should be easily solvable. We expect by modifying the binding site of the primer used for linear amplification of transposon ends that the new preparation method will be able recapitulate results from the traditional Illumina preparation method for Tn-seq. This will enable us to prepare robust Tn-seq samples from very small amounts of DNA in order to probe stress responses in single mutants as well as in microcolonies in a high-throughput manner
Thesis (MS) — Boston College, 2016
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Biology
39
Bishop, G. P., and Phillip R. Scheuerman. "Physiological Changes in Bacteria During Starvation Stress." Digital Commons @ East Tennessee State University, 1990. https://dc.etsu.edu/etsu-works/2889.
Full text
40
Bishop, G. P., and Phillip R. Scheuerman. "Physiological Changes in Bacteria During Starvation Stress." Digital Commons @ East Tennessee State University, 1991. https://dc.etsu.edu/etsu-works/2890.
Full text
41
Neto, José Freire da Silva. "Estudo do papel dos fatores sigma alternativos sE e sN de Xylella fastidiosa." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-29012008-125605/.
Full textAbstract:
Linhagens mutantes foram obtidas para os fatores sigma sE (RpoE) e sN (RpoN) da bactéria Xylella fastidiosa. O mutante rpoE mostrou-se sensível a etanol e a choque térmico. Análises de microarranjo de DNA, de RT-PCR quantitativo e mapeamento de sítios de início de transcrição permitiram definir o regulon sE em resposta ao choque térmico. Verificou-se co-transcrição entre os genes que codificam para sE, seu anti-sigma e uma protease, e sE não se mostrou auto-regulado, mas regulou o gene do anti-sigma. Análises similares às acima indicaram que o gene pilA, codificando a pilina da fímbria tipo IV, é positivamente regulado por sN, enquanto o operon codificando proteínas da fímbria tipo I é regulado negativamente, explicando a maior formação de biofilme e auto-agregação no mutante rpoN. O perfil temporal de expressão da linhagem selvagem J1a12 em carência de nitrogênio foi determinado, além de genes induzidos por carência de nitrogênio via sN. Assim, sN regula genes de fímbrias e de resposta à carência de nitrogênio em Xylella fastidiosa.Mutant strains were obtained for the sigma factors sE (RpoE) and sN (RpoN) in Xylella fastidiosa. The rpoE mutant showed to be sensitive to ethanol and heat shock. Microarray and quantitative RT-PCR analyses and determination of transcription start sites permitted to define the sE regulon under heat shock. Co-transcription of the genes encoding sE , its anti-sigma factor and a protease was observed, and sE did not present auto-regulation, but it regulated the gene encoding the anti-sigma. Similar analyses indicated that the pilA gene, encoding the pilin of the type IV fimbriae, is positively regulated by sN, while the operon encoding proteins of the type I fimbriae is negatively regulated, what explains the increased biofilm formation and auto-aggregation in the rpoN strain. Temporal expression profile of wild type strain J1a12 under nitrogen starvation was determined, as well as genes induced by nitrogen starvation via sN. Thus, sN regulates genes encoding fimbriae and genes for nitrogen starvation response in Xylella fastidiosa.
42
Di, Paolo Tiziano. "Stress response in Entamoeba histolytica." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68169.
Full textAbstract:
The heat shock response was studied in the intestinal parasitic protozoan Entamoeba histolytica. Temperature shifts from 37$ sp circ$C to 44$ sp circ$C enhanced the synthesis of five major heat shock (or stress) proteins (HSP) of 100, 50, 42, 37, and 28 kDa. Similarly, exposure of amebae to lymphokine activated macrophages and hydrogen peroxide caused HSP expression. Heat shock caused the reversible inhibition of amebic adherence to Chinese hamster ovary cells and human colonic mucin binding to trophozoites by ${>80 %}$. This was due to a decrease in the surface expression of the Gal/GalNAc adherence lectin and a marked reduction in the lectin mRNA expression. However, the presence of target Chinese hamster ovary cells during recovery at 37$ sp circ$C augmented amebic adherence. These results suggest that E. histolytica trophozoites produce a variety of HSP in response to different stimuli and can modulate the expression of the surface adherence lectin which maybe important in pathogenesis.
43
Brorsson, Camilla. "Trauma - logistics and stress response." Doctoral thesis, Umeå universitet, Anestesiologi och intensivvård, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-93324.
Full textAbstract:
Background: Trauma is a major cause of death and disability. Adverse events, such as prolonged prehospital time, hypoxia, hypotension and/or hyperventilation have been reported to correlate to poor outcome. Adequate cortisol levels are essential for survival after major trauma. In hypotensive critically ill patients, lack of sufficient amount of cortisol can be suspected, and a concept of critical illness related corticosteroid insufficiency has been proposed. Corticosteroid therapy has many adverse effects in critically ill patients and should only be given if life-saving. Correct measurement of serum cortisol levels is important but difficult in critically ill patients with capillary leakage. Estimation of the free and biologically active cortisol is preferable. In serum less than 10% of cortisol is free and biologically active and not possible to measure with routine laboratory methods. Salivary cortisol can be used as a surrogate for free cortisol, but salivary production is reduced in critically ill patients. Liver resection could reduce cortisol levels due to substrate deficiency. Aims: 1. Evaluate the occurrence of early adverse events in patients with traumatic brain injury and relate them to outcome. 2. Assess cortisol levels over time after trauma and correlate to severity of trauma, sedative/analgesic drugs and cardiovascular function. 3. Evaluate if saliva stimulation could be performed without interfering with salivary cortisol levels. 4. Assess cortisol levels over time after liver resection in comparison to other major surgery. Results: There was no significant correlation between prehospital time ³60 minutes, hypoxia (saturation <95%), hypotension (systolic blood pressure <90 mmHg), or hyperventilation (ETCO2 <4.5 kPa) and a poor outcome (Glasgow Outcome Scale 1-3) in patients with traumatic brain injury. Cortisol levels decreased significantly over time after trauma, but there was no correlation between low (<200 nmol/L) serum cortisol levels and severity of trauma. Infusion of sedative/analgesic drugs was the strongest predictor for a low (<200 nmol/L) serum cortisol. The odds ratio for low serum cortisol levels (<200 nmol/L) was 8.0 for patients receiving continuous infusion of sedative/analgesic drugs. There was no significant difference between unstimulated and stimulated salivary cortisol levels (p=0.06) in healthy volunteers. Liver resection was not associated with significantly lower cortisol levels compared to other major surgery. Conclusion: There was no significant correlation between early adverse events and outcome in patients with traumatic brain injury. Cortisol levels decreased significantly over time in trauma patients. Low cortisol levels (<200 nmol/L) were significantly correlated to continuous infusion of sedative/analgesic drugs. Saliva stimulation could be performed without interfering with salivary cortisol levels. Liver resection was not associated with low cortisol levels compared to other major surgery.
44
Silva, Sara Maria Cunha Oliveira. "Stress response of Listeria monocytogenes." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12617.
Full textAbstract:
Mestrado em Biologia Molecular e CelularThirty-five Listeria monocytogenes isolates previously collected from food (n=20) and human patients suffering from listeriosis (n=15), with different antibiotic resistance profiles were characterized and compared based on: (i) their ability to survive through sequential conditions that parallel the digestive tract; (ii) their capacity to survive extreme pH values; (iii) the potential relationship, between antibiotic resistance and the resistance of L. monocytogenes isolates to the stress conditions investigated. The response was shown to be strain- and stress-dependent and no relation between food and clinical isolates was observed (p > 0.05). The results showed that L. monocytogenes is able to survive under extreme acid and alkaline conditions and did not survive when submitted to simulated sequential gastro-intestinal transit, i.e. the activity of bile salts after combined action of hydrochloric acid and pepsin. No correlation was observed between antibiotic resistance and response to the stress conditions applied to the isolates investigated.
Trinta e cinco isolados de Listeria monocytogenes provenientes de alimentos (n=20) e pacientes humanos com listeriose (n=15) e com diferentes perfis de resistência a antibióticos foram caracterizados e comparados com base na: (i) sua capacidade de sobrevivência à passagem pelo trato gastrointestinal simulado, (ii) sua capacidade de sobrivência a condições extremas de pH, (iii) potencial relação entre a resistência a antibióticos e a resistência às condições de stresse investigadas. A resposta às várias condições de stresse demonstrou ser estirpe- e stresse-dependente e não foi observada nenhuma relação entre isolados alimentares e clínicos (p > 0.05). Os resultados mostraram que L. monocytogenes sobrevive em condições ácidas e alcalinas extremas e não sobrevive quando submetida à passagem pelo trato gastrointestinal simulado, ou seja, à atividade dos sais biliares após ação conjunta do ácido clorídrico e pepsina. Não foi observada qualquer correlação entre a resistência a antibióticos e a resposta às condições de stresse aplicadas para os isolados estudados.
45
Chen, Chun-Chun. "Response to social stress : sensory input, stress response and the neural substrates of reproductive suppression /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
46
Balhesteros, Heloise. "Análise do papel do gene cspC de Caulobacter crescentus e de sua regulação." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-03122009-112829/.
Full textAbstract:
O choque frio em bactérias causa a indução de proteínas de choque frio de baixo peso molecular (CSPs), que desestabilizam estruturas secundárias do mRNA, permitindo sua tradução. Caulobacter crescentus possui quatro genes codificando CSPs: cspA e cspB são induzidos sob choque frio, e cspC e cspD, na fase estacionária. Neste trabalho, foi determinada uma nova seqüência para o gene cspC, revelando que a proteína CspC possui dois domínios CSD, como CspD. O mutante nulo para cspC apresentou sensibilidade em baixa temperatura e menor viabilidade em fase estacionária, com alterações na morfologia. A região regulatória foi mapeada por fusões de transcrição, e uma região ativadora da expressão foi identificada, mostrando uma regulação transcricional. Algumas condições nutricionais que disparam a indução do gene foram determinadas, indicando que sua expressão é influenciada pela ausência de glicose no meio, mas não pela ausência de nitrogênio. Este perfil de indução não depende da região ativadora, que, por sua vez, é necessária para os máximos níveis de expressão.The cold shock response in bacteria involves the expression of cold shock proteins (CSPs), which destabilize secondary structures on mRNAs, allowing their translation. Caulobacter crescentus possesses four genes encoding CSPs: cspA and cspB are induced upon cold shock, while cspC and cspD are induced at stationary phase. In this work, a new sequence for the coding region of the cspC gene was determined, revealing that CspC contains two cold shock domains, like CspD. A null cspC mutant was sensitive to low temperature, presented reduced viability at stationary phase, and altered morphology. The regulatory region of cspC was mapped by transcriptional fusions, identifying a region responsible for activation of cspC expression, suggesting a transcriptional regulation. Some nutritional conditions triggering cspC induction were determined, indicating that its expression is influenced by glucose starvation, but not by nitrogen starvation. This expression profile was not dependent on the activation region, which, in turn, was required for maximum levels of expression.
47
Al-Humiany, Abdulrahman Abdullah. "A comparison of the responses to environmental stress of the gram-positive bacterium Staphylococcus xylosus and the gram-negative bacterium Halomonas halo." Thesis, University of Sheffield, 1999. http://etheses.whiterose.ac.uk/10228/.
Full textAbstract:
Abdulrahman Al-Humiany (1999) A Comparison of the Responses to Enviromental Stress of the Gram-Positive Bacterium Staphylococcus xylosus and the Gram-Negative Bacterium Halomonas Halo. PhD Thesis, Department of Molecular Biology and Biotechnology, University of Sheffield. Salt tolerance of the Gram-negative bacterium, Halomonas Halo, was compared with the salt tolerance of a newly isolated Gram-positive coccus Staphylococcus xylosus. Both organisms grew over a range of salinities from 0.1 - 3.0 M NaCI in both rich medium containing yeast extract and in minimal medium. In the absence of yeast extract, growth of S. xylosus was very slow at 3.0 M NaCl and its optimum salinity for growth was 0.1 M NaCl, whereas Halomonas Halo showed optimum growth at 0.5 M NaCl. Growth experiments replacing NaCI with KC1 and the effect of Na+ on the rate of respiration showed that Halomonas Halo had a greater requirement for Na+ for growth than S. xylosus. When betaine was added to the minimal medium, it greatly increased the growth rate of both organisms at 3M NaCl. The precursor of betaine, choline, was also effective in increasing the growth rate of Halomonas Halo, but was much less effective for S. xylosus. Both organisms transported betaine into the cells by an energy dependent transport system; transport rates were broadly similar, but it appeared that the halotolerant S. xylosus took up betaine more efficiently than Halomonas Halo. Halomonas Halo and S. xylosus were shown to grow across a pH range from 5.5 - 8.5, but S. xylosus showed optimum growth across the full range whereas Halomonas Halo showed a distinct optimum at pH 7.0. The proton motive force (Ap) was found to be low in both organisms and at pH 8.5, it fell below the theoretical minimum (150 mV) which is required for ATP synthesis. Ap was significantly reduced by the inhibitor carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and to a much lesser extent by monensin. Both inhibitors completely stopped the growth of both organisms at pH 7.0. The possibility that compatible solutes may protect enzymes from thermal denaturation was examined, but the results were inconclusive.
48
Staroń, Anna [Verfasser], and Thorsten [Akademischer Betreuer] Mascher. "Phylogenetic and functional analyses of stress-responsive bacterial transmembrane signal transducing systems / Anna Staron. Betreuer: Thorsten Mascher." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2012. http://d-nb.info/1027669476/34.
Full text
49
Crowther, Michael. "Novel unconventional T-cells in response to bacteria and cancer." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/119167/.
Full textAbstract:
Conventional T-cells respond to peptide antigens presented by person-specific Human Leukocyte Antigens (HLAs) and therefore therapies that harness such cells may only be applicable to a minority of individuals. Unconventional T-cells could bypass this limitation to provide an opportunity for population-wide disease treatments. Exploitation of such T-cells first requires a detailed study of the unconventional T-cells involved in the immune response. I therefore sought to characterise novel invariant T-cells generated in response to varied disease agents. Results - An optimised protocol for procurement of disease-relevant unconventional T-cells was established and used to generate T-cell lines and clones of interest. T-cell receptor (TCR) sequencing of unconventional T-cell populations revealed a predominance of mucosal-associated invariant cells and Vγ9Vδ2 T-cells. Enrichments for other shared TCR clonotypes included TRAV21 and TRAV13-1 genes, which have some evidence of an invariant nature. I identified an interesting T-cell clone that was capable of recognising a broad range of target cells through a novel mechanism. The ligand recognised by these T-cells was identified using a whole genome CRISPR approach. Further studies confirmed the nature of the ligand and that recognition was dependent on a new subtype of TCR that was present in all donors tested. Conclusions - The field of unconventional T-cells is rapidly expanding, with novel invariant T-cells proving to be a much greater part of the T-cell repertoire than previously estimated. New and undiscovered invariant T-cell subsets are likely to provide exciting novel immunotherapies and bypass the limitation of HLA-restriction that is associated with conventional T-cell recognition of peptide-major histocompatibility complex ligands.
50
Lindahl, Andreas. "Neuroendocrine Stress Response after Burn Trauma." Doctoral thesis, Uppsala universitet, Plastikkirurgi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-198466.
Full textAbstract:
Some aspects of the stress response during acute intensive care for severe burns are described and quantified by measuring hormonal and neuroendocrine patterns and relating these to organ function in the short term. This includes an assessment of whether there are markers for the severity of stress that are better than conventional descriptors of the severity of a burn in predicting failing organ function. P-CgA after a major burn injury is an independent and better predictor of organ dysfunction assessed as SOFA score than the traditionally used TBSA% burned. The results also suggest that the extent of neuroendocrine activation is related to organ dysfunction, and this motivates a more extensive effort to evaluate P-CgA as a prognostic marker with respect to mortality and long-term outcome. P-NT-proBNP exhibited a complex pattern with considerable inter-individual and day-to-day variations. Values of P-NT-proBNP were related to size of burn, water accumulation and systemic inflammatory response. A considerable covariation with trauma response and SOFA scores was observed in day by day analyses, but with weight change only on day 2. Maximum P-NT-proBNP showed a stronger correlation with SOFA score on day 14, with mortality, and with LOS, than did age and TBSA% burned. High values were also independent predictors of all subsequent SOFA scores up to two weeks after injury. P-NT-proBNP and NT-proANP reflect and predict organ function after burn injury similarly, notwithstanding a significantly larger intra-individual variability for P-NT-proBNP. P-NT-proBNP, but not NT-proANP, reflects the systemic inflammatory trauma response. Free cortisol concentration was related to the size of burns, as was the circadian cortisol rhythm. This effect of burn size was, at least in part, related to its effect on organ function. This thesis points to the fact that the stress response is richly interwoven, and cannot be adequately assessed by one biomarker only. All biomarkers studied here can be viewed as representing efferent limbs of the stress reaction, and they would need to be supplemented by biomarkers representing individual physiologic responses that follow the stress signaling.