Dissertations / Theses: 'Bacterial Interactions'

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McQuillan, Jonathan. "Bacterial-nanoparticle interactions." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/3101.

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Bionanotechnology is an intersection between biology and nanotechnology, a field in which novel applications for very small materials are being realised at an alarming rate. Nanoparticles have 3 dimensions that can be measured in nanometers, their small size conferring upon them different properties from individual atoms or the bulk material. The interactions between these unique materials and microorganisms are often toxic, thus have been exploited for antimicrobial applications. However, there is a considerable paucity of data for the underlying molecular mechanisms. This study has been carried out to investigate the interactions that occur between nanoparticles and bacteria with the objective of identifying these toxicological mechanisms and novel nanoparticle effects, using the model Gram negative organism Escherichia coli K12. This study has identified metal nanoparticles that are a superior vehicle for the delivery of toxic metal ions to E. coli. The nanoparticles associate with the bacterial surface, but do not cross the cell wall. They then dissolve, releasing a concentration of metal ions that accumulate at the bacterial-nanoparticle interface, enhancing the antibacterial efficacy compared to the concentration of metal ions in the bulk solution phase. Measurement of the whole transcriptome response to silver nanoparticles in comparison to the silver ion indicates that the different modes of ion delivery may induce a differential stress response. Moreover, this data identifies molecular mechanisms that are involved in the toxicity of this metal that is now becoming increasingly prevalent in society. The dissolution based toxic effects of zinc oxide nanoparticles are augmented by an interaction with ultra-violet light, offering an alternative mode for nanoparticle toxicity.

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de, Klerk Nele. "Host-bacteria interactions : Host cell responses and bacterial pathogenesis." Doctoral thesis, Stockholms universitet, Institutionen för molekylär biovetenskap, Wenner-Grens institut, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-126425.

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Helicobacter pylori colonizes the human stomach, where it causes gastritis that may develop into peptic ulcer disease or cancer when left untreated. Neisseria gonorrhoeae colonizes the urogenital tract and causes the sexually transmitted disease gonorrhea. In contrast, Lactobacillus species are part of the human microbiota, which is the resident microbial community, and are considered to be beneficial for health. The first host cell types that bacteria encounter when they enter the body are epithelial cells, which form the border between the inside and the outside, and macrophages, which are immune cells that engulf unwanted material. The focus of this thesis has been the interaction between the host and bacteria, aiming to increase our knowledge of the molecular mechanisms that underlie the host responses and their effects on bacterial pathogenicity. Understanding the interactions between bacteria and the host will hopefully enable the development of new strategies for the treatment of infectious disease. In paper I, we investigated the effect of N. gonorrhoeae on the growth factor amphiregulin in cervical epithelial cells and found that the processing and release of amphiregulin changes upon infection. In paper II, we examined the expression of the transcription factor early growth response-1 (EGR1) in epithelial cells during bacterial colonization. We demonstrated that EGR1 is rapidly upregulated by many different bacteria. This upregulation is independent of the pathogenicity, Gram-staining type and level of adherence of the bacteria, but generally requires viable bacteria and contact with the host cell. The induction of EGR1 is mediated primarily by signaling through EGFR, ERK1/2 and β1-integrins. In paper III, we described the interactions of the uncharacterized protein JHP0290, which is secreted by H. pylori, with host cells. JHP0290 is able to bind to several cell types and induces apoptosis and TNF release in macrophages. For both of these responses, signaling through Src family kinases and ERK is essential. Apoptosis is partially mediated by TNF release. Finally, in paper IV, we showed that certain Lactobacillus strains can reduce the colonization of H. pylori on gastric epithelial cells. Lactobacilli decrease the gene expression of SabA and thereby inhibit the binding mediated by this adhesin.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: Manuscript.

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Asif, Muhammad. "Acanthamoeba and the bacterial pathogen interactions." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/20427.

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The present study investigates Acanthamoeba-bacteria interaction and how this relation can influence human health aiming at the influence of bacteria on Acanthamoeba in terms of their isolation and diversity, and the effect of Acanthamoeba on bacteria focusing on two emerging human bacterial pathogens Arcobacter butzleri and Rhodococcus equi. To first objective was investigated by the test question “can the presence of a particular type of bacteria play role in the diversity of Acanthamoeba by masking and/or favouring certain genotypes of Acanthamoeba?” To answer this, two different bacteria the Gram+ve Enterococcus the Gram-ve Arcobacter were used as food source for isolation of Acanthamoeba from 102 soil samples while E. coli was used as control. It was found that the presence of different bacteria could affect the isolation of genotypes specially the subgroups and subtypes of Acanthamoeba as manifested by greater diversity of 18S rRNA sequences of Acanthamoeba isolated from environmental samples on Arcobacter (Arc) and Enterococcus (Ent) than those isolated on E. coli (Eco). The Eco isolates consisted of only T4 > T11=T13 compared to Ent isolates with T4 > T16 > T13/16 and the Arc isolates which comprised of T4 > T2 > T2/6 = T13 > T13/16. The T13/16 were the intermediate sequence types with no match to any T types. There were also considerable differences among the T4 subgroups; the Eco isolates consisted of T4-A > T4-B > T4-N > T4- E > T4-D > T4-C while Ent isolates comprised of T4-A > T4-C=T4-D=T4-E=T4-N > T4-B and the Arc isolates had only T4-E > T4-A > T4-B > T4-N. In both Eco and Ent isolates 11 subtypes were recovered with T4-36 being the most abundant, however, in Arc isolates eight subtypes were recovered with T4-12 as the most abundant. The non-Eco isolates were also different in their bacterial endosymiotic profile from Eco isolates with Arc isolates having the greatest proportion of bacterial endosymbionts (15.7%) as compared to 7.8% of Eco and 12.9% of Ent isolates. Together these results indicate a prominent role of prey bacteria on favouring certain genotypes and thus compelling consideration for use of different types of bacteria for isolation of Acanthamoeba to help surface the masked populations as well for more realistic prevalence that will help in better designing of prevention and control strategies. The influence of Acanthamoeba on bacteria was investigated for A. butzleri and R. equi both of which appeared to exploit the former as an environmental reservoir and for modulation of their pathogenic potential. A. butzleri which are closely related to Campylobacter, appeared to have a smooth interaction with Acanthamoeba. They were shown to be easily located through chemotaxis, readily attached and internalized using monosaccharide receptors and a complex phagocytic process, and could survive/proliferate in Acanthamoeba by defying the intra-vacuolar killing processes. Intracellular survival in Acanthamoeba did play a role in promoting the pathogenicity of these bacteria enabling them to survive more than three times longer. Co-culturing of the two organisms also seemed to benefit the bacteria but not Acanthamoeba. A. butzleri were found to be able to sense the environmental changes and thus modulate their virulence, a feature that together with selection pressure for intracellular survival in Acanthamoeba can cause rapid adaptation to intra-amoebal environment and enhance the pathogenic potential of these bacteria for humans and animals. Exploitation of Acanthamoeba for survival was also found to be exhibited by the Mycobacterium-resembling Gram+ve R. equi by utilizing similar strategies for survival/proliferation as used for macrophages, which involved the definite presence of virulence plasmid and its activation at higher temperatures. Moreover, similar genes (vapA, vapC and vapF) were found to play role in intracellular survival in both the macrophages and amoeba cells. The intra-amoebal survival/proliferation capabilities of A. butzleri and R. equi appear to support the notion that free living protists like Acanthamoeba act as environmental reservoirs/virulence trait selectors and are strong candidates for the “missing link” between the ecology and pathology of these emerging pathogenic pathogens. Overall, the observations made in this study explore the vital role of Acanthamoeba-bacteria interaction not only mutually on each other but as a consequence the impact on human health either as a result of masked genotypes in clinical diagnosis of Acanthamoeba or due to environmental reservoir role of Acanthamoeba in selecting virulence traits of bacteria, can pose serious challenges leaving ample opportunities for more emerging bacterial pathogens. These observations call for revising the protocols for Acanthamoeba prevalence, eradication and control strategies.

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Carlin, Aaron Foster. "Siglec interactions with a sialylated bacterial pathogen." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3263070.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed April 9, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

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Gagnon, Jean-Nicolas. "Molecular interactions of bacterial outer membrane proteins." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81333.

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Transport of iron-siderophores and vitamin B12 across the outer membrane (OM) of Gram-negative bacteria requires energy from the proton motive force delivered by the TonB/ExbB/ExbD complex. TonB-dependent OM receptors such as FhuA, FepA, FecA and BtuB possess a Ton box: a conserved motif located proximal to their N-terminus that has been shown to interact with TonB. However, other sites on OM receptors have been proposed to participate in interactions with TonB. To identify novel sites of interactions with TonB, we selected TonB-binding peptides from a random library of peptides displayed on phages. Fifteen peptides displayed sequence similarities to known TonB-dependent OM receptors. Of the fifteen, eight were mapped to regions of FhuA, FepA and FecA for which crystal structures are available. DNA sequences for selected peptides were fused to malE and displayed at the N-terminus of the E. coli maltose binding protein (MBP) for further characterization. Surface plasmon resonance experiments revealed that when the peptides were monovalently displayed on MBP, they retained TonB-binding activity thereby permitting assessments of their binding characteristics. In vitro and in vivo assays demonstrated that only FhuA-mapping peptides could disrupt TonB-FhuA interactions, indicating that TonB selectively binds to multiple regions distinct for each OM receptor.

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Banda, Srikanth. "Protein-protein Interactions of Bacterial Topoisomerase I." FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3378.

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Protein-protein interactions (PPIs) are essential features of cellular processes including DNA replication, transcription, translation, recombination, and repair. In my study, the protein interactions of bacterial DNA topoisomerase I, an essential enzyme, were investigated. The topoisomerase I in bacteria relaxes excess negative supercoiling on DNA and maintains genomic stability. Investigating the PPI network of DNA topoisomerase I can further our understanding of the various functional roles of this enzyme. My study is focused on topoisomerase I of Escherichia coli and Mycobacterium smegmatis. Firstly, we have explored the biochemical mechanisms for an interaction between RNA Polymerase, and topoisomerase I in E. coli. Molecular docking and molecular dynamic simulations have predicted that the interactions are mediated through electrostatic, and hydrogen bonding. The predicted Lysine residues (K627, K664) of topoisomerase I that are involved in the electrostatic interactions were mutated to Alanine, and its effect on the binding efficiency with RNA polymerase was reported. In a separate study, PPI partners of topoisomerase I in mycobacteria were identified. Knowledge gained from the study can provide valuable insights into the physiological functions of a validated drug target, DNA topoisomerase I, in pathogenic mycobacteria. Co-immunoprecipitation and pull-down assays were coupled to mass spectrometry for identification of the protein partners of mycobacterial topoisomerase I. The study has identified RNA polymerase, and putative helicases (DEAD/DEAH BOX helicases) as potential protein partners of mycobacterial topoisomerase I. My results indicated that the tail region of the CTD-topoisomerase I was required for direct physical interaction with the RNAP beta’ subunit. My studies have also verified the physiological relevance of the topoisomerase I - RNA polymerase interactions for survival under antibiotic, and oxidative stress. Lastly, I report a direct physical interaction between E. coli topoisomerase I and RecA by pull-down assays. Previous studies have shown that RecA, a DNA repair protein, can stimulate the relaxation activity of E. coli topoisomerase I. Our new results showed that the stimulatory effect can be attributed to the physical interaction of topoisomerase I with RecA.

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Kirke, David F. "Protein-nucleic acid interactions regulating bacterial quorum sensing." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364668.

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Packer, Samantha. "Bacterial-epithelial cell interactions in the periodontal diseases." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1445766/.

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Periodontal diseases result from a complex interaction between a biofilm containing commensal and periopathogenic bacteria and the host innate and acquired defense systems. The interaction of oral commensal and pathogenic bacteria and their effect on ' cell behaviour, particularly the synthesis of antibacterial and inflammatory molecules, has been the focus of this project. The messenger RNA (mRNA) and protein expression of human beta-defensin and pro-inflammatory cytokine mRNA in the gingiva of patients suffering from the periodontal diseases was also determined. Patients suffering periodontal diseases showed increased mRNA expression of human beta-defensins and cytokines compared to controls, however, there was no difference in human beta-defensin protein expression between diseased and control tissue samples. Further studies were then carried out to determine the effect of oral commensal and periopathogenic bacteria and their surface components on oral epithelial cells (OECs). An oral squamous carcinoma cell line was found to produce IL-8 protein and express mRNA for human beta-defensin 2 (hpD-2), both of which were induced by several oral bacterial cell surface components, including LPS. The stimulatory effect of LPS was subsequently found to involve the LPS receptor, CD 14. The presence of toll-like receptor mRNA was also demonstrated and results showed that their expression may be regulated by bacteria associated molecular patterns. Both live- and heat-killed oral bacterial pathogens, A. actinomycetemcomitans and P. gingivalis induced production of IL-8 protein and hpD-2 mRNA from OECs. Exposure to the oral commensals S. sanguis and S. gordonii resulted in a decrease in the production of IL-8 mRNA from OECs, whilst heat-killed S. sanguis upregulated hpD-2 mRNA. A highly invasive strain of A. actinomycetemcomitans was shown to adhere to OECs to a greater degree, and also led to a greater induction of hpD-2 mRNA and IL-8 protein compared to a non-invasive strain. Further, isogenic mutants of the oral commensal S. gordonii DL1 Challis, deficient in the production of antigen I/II-family proteins SspA and SspB and the fibrillar cell surface proteins CshA and CshB, showed reduced adhesion to OECs. All strains had comparable effects on IL-8 protein and hpD-2 mRNA expression in OECs. The results presented in this thesis demonstrate the expression profile of human beta- defensins and cytokines in healthy and diseased gingival tissue. hpD-2 has been shown to be upregulated in oral epithelial cells by a range of oral commensal and pathogenic bacteria and their products. It has also been shown that the invasive nature of oral bacteria may contribute to increased expression of hpD-2 messenger RNA in oral epithelial cells. The upregulation of hpD-2 mRNA by a wide variety of components, bacterial or otherwise in oral epithelial cells may have therapeutic potential, however further studies would need to be carried out to determine the correlation between mRNA and protein expression of hpD-2.

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Marcinkiewicz, Ashley. "Bacterial and phage interactions influencing Vibrio parahaemolyticus ecology." Thesis, University of New Hampshire, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10127507.

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Vibrio parahaemolyticus, a human pathogenic bacterium, is a naturally occurring member of the microbiome of the Eastern oyster. As the nature of this symbiosis in unknown, the oyster presents the opportunity to investigate how microbial communities interact with a host as part of the ecology of an emergent pathogen of importance. To define how members of the oyster bacterial microbiome correlate with V. parahaemolyticus, I performed marker-based metagenetic sequencing analyses to identify and quantify the bacterial community in individual oysters after culturally-quantifying V. parahaemolyticus abundance. I concluded that despite shared environmental exposures, individual oysters from the same collection site varied both in microbiome community and V. parahaemolyticus abundance, and there may be an interaction with V. parahaemolyticus and Bacillus species. In addition, to elucidate the ecological origins of pathogenic New England ST36 populations, I performed whole genome sequencing and phylogenetic analyses. I concluded ST36 strains formed distinct subpopulations that correlated both with geographic region and unique phage content that can be used as a biomarker for more refined strain traceback. Furthermore, these subpopulations indicated there may have been multiple invasions of this non-native pathogen into the Atlantic coast.

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Tsang, Kenneth Wah Tak. "Bacterial interactions with human respiratory mucosa in vitro." Thesis, University of Glasgow, 1995. http://theses.gla.ac.uk/8346/.

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The theme of this thesis is to study the interactions of non-typable Haemophilus influenzae (NTHi) and Pseudomonas aeruginosa (PA) with intact human respiratory mucosa in vitro. Recent evidence suggests that bacteria are mainly associated with respiratory mucus during exacerbation of chronic bronchitis but penetration of antibiotics into respiratory mucus is generally poor. A study was therefore performed to evaluate the effects of 0.25 and 0.5 minimal inhibitory concentrations of amoxycillin, loracarbef (a new carbacephem) and ciprofloxacin on NTHi infection of adenoid organ cultures in an agar-embedded model in which only the intact respiratory mucosa was exposed to bacteria-containing culture medium. The results from this study may help explain the clinical efficacy of antibiotics in treatment of bronchial infection despite poor antibiotic penetration into respiratory secretions. By using the same organ culture model the effects of NTHi infection of intact human bronchial mucosa was also studied. NTHi infection of bronchial organ cultures was associated with ultrastructural damage compared with uninfected organ cultures after 24h incubation. This damage was similar to the pattern observed in adenoid organ cultures described earlier. Similar experiments using nasal turbinate tissue showed virtually no adherence of NTHi to nasal respiratory mucosa suggesting that there may be a difference in epithelial surface receptors for NTHi between adenoid and nasal turbinate mucosa. Infection of adenoid organ cultures with an air-mucosal interface by PA caused significant ultrastructural damage (mitochondrial damage, loss of cilia, cytoplasmic blebbing and extrusion of cells from the epithelial surface) and slowing of ciliary beat when assessed by transmission electron and light microscopy respectively after 8h incubation. PA was found to cause disruption of epithelial tight junctions and adhere to basement membrane collagen. A matrix-like material was probably produced by PA which bridged PA with respiratory mucosa and might therefore be a PA adhesin. PA formed bacterial biofilms on the surface of respiratory mucosa that might have hindered its removal by the mucociliary clearance mechanism. These findings might help explain the difficulty in eradicating PA from the lower respiratory tract of patients with cystic fibrosis and bronchiectasis. The organ culture model with an air-mucosal interface was also used to study the effects of a bacterial toxin on intact human respiratory mucosa. An exotoxin of PA, pyocyanin was found to cause significant mucosal damage to adenoid organ cultures when assessed by transmission electron microscopy. Moreover, by using a newly developed transmission electron microscopy method to assess orientation of central microtubules of cilia and foot processes, pyocyanin was found to cause significant disorientation of the central microtubules of respiratory cilia but not the foot processes. PA pyocyanin may therefore have a role in the pathogenesis of PA infection in vivo. By using these organ culture models of intact human respiratory mucosa, bacteria interactions with human respiratory mucosa can be studied using the transmission, scanning electron, and light microscopy methods described in this thesis. Potential virulent factors for NTHi and PA can be tested and the mechanisms of bacterial pathogenesis can be studied further to advance current understanding of bacterial interactions with the human respiratory tract mucosa that may lead to the development of novel therapies.

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Strauss, Joshua. "Investigating bacterial lipopolysaccharides and interactions with antimicrobial peptides." Worcester, Mass. : Worcester Polytechnic Institute, 2009. http://www.wpi.edu/Pubs/ETD/Available/etd-012009-120216/.

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Rassner, Sara. "Influences of bacterial resources on the dynamics of virus-bacterium interactions in aquatic ecosystems." Thesis, Aberystwyth University, 2010. http://hdl.handle.net/2160/843eeee2-7b1c-4d03-80b4-77ffb5b186a9.

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Chaves, Olarte Esteban. "Glucosyltransferase toxins from clostridia : molecular interactions with cells /." Stockholm, 2000. http://diss.kib.ki.se/2000/91-628-4537-3/.

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Shanthalingam, Sudarvili. "Mannheimia haemolytica leukotoxin host cell receptor interactions /." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Dissertations/Spring2010/s_shanthalingam_020210.pdf.

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Bjertsjö, Rennermalm Anna. "Staphylococcal cell wall associated proteins : characteristics and host interactions /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-542-9/.

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Atabek, Arzu. "Investigating bacterial outer membrane polymers and bacterial interactions with organic molecules using atomic force microscopy." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-082206-162049/.

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Patten, Daniel. "Interactions of intestinal epithelial cells with bacterial extracellular products." Thesis, University of Huddersfield, 2013. http://eprints.hud.ac.uk/id/eprint/18071/.

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The enteric microflora represents one of the densest microbial populations in the biological world; as a consequence, the intestinal immune system is constantly exposed to high concentrations of antigenic materials. One of the major frontline defences in the innate immune system is the intestinal epithelial layer, which presents both a physical barrier and an immune sensor to the antigens of the lumen. The latter function is performed by the expression of pattern recognition receptors, which recognise a wide variety of bacterial antigens, and the production of inflammatory cytokines, which stimulate, or inhibit, inflammation. The overall aim of the present study was to investigate the immunomodulatory potential of extracellular products, from non-pathogenic bacteria, with intestinal epithelial cells. Two in vitro human intestinal epithelial cell lines HT29-19A and Caco-2 were shown to exhibit different expression levels of Toll-like receptors (TLRs) and the inflammatory cytokines, interleukin (IL)-8 and IL-10. These differences were reflected in their sensitivity (monitored by IL-8 release) to known TLR agonists, isolated from pathogenic bacteria. Caco-2 cells were also shown to form physiologically active tight junctions, with the formation and maintenance of domes. Both cell lines exhibited sensitivity to the cytotoxic extracellular products of the enteropathogen Clostridium difficile. Extracellular products, in crude cell-free supernatants and bacterial sonicates, from the commensal Gram-negative bacterium Escherichia coli C25, significantly increased IL-8 release in both cell lines. Lipopolysaccharides and membrane vesicles were shown to contribute to the proinflammatory effects of C25-derived extracellular products. These extracellular products were also shown to regulate bacterial internalisation in both cell lines. Crude cell free supernatants and bacterial sonicates from two lactobacilli strains Lactobacillus acidophilus 5e2 and Lactobacillus helveticus sp. Rosyjski were also found to be biologically active, stimulating IL-8 release and TLR expression modification in both intestinal epithelial cell lines. In addition, ultrapure EPSs, isolated from these lactobacilli strains, were also found to possess immunomodulatory potential. HT29-19A cells, pre-treated with EPSs, were found to be ‘primed’ to bacterial agonists, peptidoglycan and flagellin, with a significantly potentiated release in IL-8 observed. Finally, EPSs were also found to modify bacterial adherence and internalisation in both cell lines. In conclusion, data presented in this investigation has shown that the use of the intestinal epithelial cell lines, HT29-19A and Caco-2, presents a reasonable model for investigating the interaction of bacterial extracellular products with the intestinal epithelium. Additionally, it has demonstrated that extracellular products, isolated from non pathogenic, enteric-associated bacteria, possess immunomodulatory potential in vitro. If these effects were also to occur in vivo, then they could potentially contribute to intestinal homeostasis and the innate ‘priming’ of the epithelial layer to pathogens and their products.

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Neumann, Anthony. "Bacterial interactions with anthracene in a model soil system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq22647.pdf.

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Zhang, Quan-Guo. "Diversity and competitive interactions in experimentally evolved bacterial populations." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:922d763d-3d66-40c8-96d3-5b8e95e24fe4.

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Laboratory bacterial populations provide ideal opportunities to experimentally test theories in ecology and evolutionary biology. I used a model laboratory microbial system, Pseudomonas fluorescens SBW25, to address an array of questions on the origin, maintenance, and functional role of biodiversity, and the evolution of biotic interactions. My thesis reports experiments with the following conclusions. (1) The extent of diversification in P. fluorescens populations is not affected by the presence of an interspecific competitor P. putida, although the early stage of the diversification in one environment (spatially homogeneous environment) could be speeded up by the competitor. (2) Niche and neutral mechanisms simultaneously contribute to the maintenance of phenotypic diversity in P. fluorescens populations; but the operation of niche processes does not lead to a positive effect of biodiversity on ecosystem functioning. (3) The competitive interactions among bacterial phenotypes are generally transitive, and competitive hierarchies inferred from pair-wise competition are fairly consistent to those from multi-species competition. (4) The niche complementarity and selection effects evaluated by random assembly biodiversity experiments can be used to predict the functional consequences of particular non-random species extinction scenarios. (5) P. fluorescens does not show an evolutionary trade-off in using several carbon substrates (glucose, galactose and trehalose), and evolution in environments containing these resources results in imperfect generalists; migration among populations may speed up fitness evolution of some generalists. (6) Biofilm formation at the air-broth interface by wrinkly spreader phenotypes in P. fluorescens is a cooperative behaviour which is costly to individuals but benefits the group; this behaviour could be exploited by smooth morph phenotypes. The cooperators and cheats in this system show reciprocal antagonistic coevolution in resistance and cheating performance.

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O'Brien, G. J. "Airway epithelial cells : interactions with neuropeptides and bacterial products." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421010.

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Ferguson, Anna Louise. "Interactions of bacterial sigma subunits with core RNA polymerase." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341839.

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Watson, Ashley James. "Stability and interactions of the purple bacterial reaction centre." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424644.

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McCarvil, James. "Bacterial interactions with metals in the activated sludge system." Thesis, Glasgow Caledonian University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377697.

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Eaton, Anna Kolesar. "Binding interactions in the bacterial chemotaxis signal transduction pathway." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8928.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Cell Biology and Molecular Genetics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Kudahl, Ulrich Johan. "A computational biology approach to studying algae-bacterial interactions." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/276956.

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Microalgae have a profound effect on the world due to their large contribution to net carbon fixation. Although they are phototrophic, more than 50% of microalgae are thought to depend on external supply of metabolites such as B-vitamins. In oceans, algae are therefore often found together with a community of bacteria and form intricate networks where metabolites are exchanged. Currently, only a fraction of the related mechanisms and metabolite exchanges between algae and bacteria have been uncovered and many more are likely to exist. The work presented in this thesis is based on a model system for algae-bacterial interactions made up of the green alga, Lobomonas rostrata and the alpha-proteobacterium Mesorhizobium loti. In the model system, it is known that the bacterium provides vitamin B12 to the alga and itself, whilst the alga provides fixed carbon. I have applied methods from the field of computational biology to study the interactions between these organisms and other similar partnerships, with the aim of uncovering new insights. The thesis is made up of three research chapters, each focused on using a specific method to study algae-bacterial interactions. I developed a genome scale metabolic model of metabolism of M. loti that enabled simulation of growth. The model simulates 1908 enzymatic reactions and takes 1804 metabolites into account. Using the model, I simulated growth of the bacterium on 1018 different substrates with the aim of identifying substrates supplied by L. rostrata when the two organisms are co-cultured. In addition, I carried out a set of simulations studying the bacterium’s ability to produce B12 from 1368 different substrates. The modelling efforts in this project was successful in enabling simulations, but it was not possible to validate the simulations with experimental data. A transcriptomics experiment was undertaken with the aim of identifying genes related to the interaction between L. rostrata and M. loti. In the experiment, the partners from the model system was grown in axenic and co-culture conditions and RNA samples were taken from each state. Using RNA-seq, the RNA samples were sequenced and from this a candidate transcriptome was created. The expression of each putative gene was then quantified and differentially expressed genes were identified. Based on sequence similarity, candidate functions were assigned where possible. In the analysis of differentially expressed genes, it was found that there appears to be an increased expression of a transporter responsible for uptake of the plant hormone, auxin. Currently, only a small fraction of all bacteria has been shown to produce B12 and it is not clear in which phylogenetic groups this is a common trait. I therefore applied methods from comparative genomics to study the synthesis of this metabolite in more than 8000 bacterial species. This involved developing a computational framework that allowed me to search for the presence of more than 50 genes in more than 8000 genomes in a rapid manner. I found that 37.2% of bacteria can synthesis B12 and that this capability is very common in some phylogenetic groups such as Cyanobacteria, but extremely rare in others such as Lactobacillus. I was also able to confirm that cyanobacteria are not able to make cobalamin, a variant of B12 used by eukaryotic algae, and thus they are unlikely to support algal growth in the photic zone. In the final section of the thesis, I discuss the application of computational biology methods in this field and summarise my experience from applying genome scale modelling, comparative genomics and transcriptomics to study algae-bacterial interactions.

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Habeeb, Fatema. "Bacteria-cytokines interactions : effect of normal bacterial flora of pathogenic bacteria on pro-inflammatory cytokines production in human blood." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501921.

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Qi, Xiaolin. "Enzyme-substrate interactions in PC1 #beta#-lactamase catalysis." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315617.

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Eberhard, Thomas Herrman. "Bacterial interactions with the fibrinolytic system and with the extracellular matrix /." Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3422-3/.

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Castaldo, Gaetano. "Studying protein interactions of a bacterial type II polyketide synthase." Thesis, University College London (University of London), 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500311.

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Daunorubicin (DNR) and its C-14 hydroxylaled derivative doxorubicin (DXR) a are the most widely used anthracyclines as anti-tumour agents. DNR and DXR are produced by the soil bacteria Streptomyces peucetius through a biosynthetic pathway that employs a type II polyketide synthase (PKS). Type II PKSs consist of several discrete, monofunctional proteins that form a dissociable complex. Studies on enzyme complex formation and substrate channelling are essential for a better understanding of metabolism and could lead to the generation of novel compounds by 'combinatorial' biosynthesis.

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Curry, Stephen. "The interactions of general anaesthetics with a bacterial luciferase enzyme." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47396.

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Ahmad, Asma. "Protein-protein interactions in the bacterial type VI secretion system." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4811/.

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El-Shetehy, Mohamed H. "Molecular and Biochemical Signaling Underlying Arabidopsis-Bacterial/Virus/Fungal Interactions." UKnowledge, 2016. http://uknowledge.uky.edu/plantpath_etds/19.

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Systemic acquired resistance (SAR) is a form of inducible defense response triggered upon localized infection that confers broad-spectrum disease resistance against secondary infections. Several factors are known to regulate SAR and these include phenolic phytohormone salicylic acid (SA), phosphorylated sugar glycerol-3-phosphate (G3P), and dicarboxylic acid azelaic acid (AzA). This study evaluated a role for free radicals nitric oxide (NO) and reactive oxygen species (ROS) in SAR. Normal accumulation of both NO and ROS was required for normal SAR and mutations preventing NO/ROS accumulation and/or biosynthesis compromised SAR. A role for NO and ROS was further established using pharmacological approaches. Notably, both NO and ROS conferred SAR in a concentration dependent manner. This was further established using genetic mutants that accumulated high levels of NO. NO/ROS acted upstream of G3P and in parallel to SA. Collectively, these results suggest that NO and ROS are essential components of the SAR pathway.

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Adams, Diane. "Host plant effects on an aphid-bacterial symbiosis." Thesis, University of York, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337152.

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Lopez, Hector Matias. "Influence of the coupling between flow and bacteria on the fluid rheology and on bacterial transport." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112168.

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Le transport des micro-organismes, comme par exemple les bactéries, par un fluide se retrouve au centre de thématiques de recherche dans des domaines aussi variés que de la biologie, l’écologie, l’ingénierie et la médecine.Ce manuscrit résume mon étude expérimentale du couplage entre le mouvement microscopique de la nage des bactéries et le mouvement advectif de l’écoulement.La première partie du manuscrit porte sur la rhéologie des suspensions d’E. coli sous faible taux de cisaillement. Pour cette condition, j’ai montré que les perturbations hydrodynamiques induites par la nage réduisent fortement la viscosité. Cet effet peut-être si important pour qu’il soit suffisant pour compenser entièrement la perte visqueuse due au cisaillement.La seconde partie traite des expériences d’écoulement réalisées dans un canal capillaire. Pour cette géométrie, j’ai examiné le couplage pour des écoulements caractérisés par un plus fort taux de cisaillement. Le suivi des trajectoires et le dénombrement des bactéries m’ont permis de mettre en évidence l’existence d’une composante de vitesse normal à la direction de l’écoulement. Cette dernière montre que les bactéries suivent des trajectoires hélicoïdales qui s’enroulent autour du centre du capillaire d’une façon antihoraires. Cette nouvelle composante est corrélée à la migration préférentielle des bactéries dans une couche de localisation proche de la paroi du canal.Les couplages rhéotactiques bactéries/fluide que j’ai étudiés doivent avoir des conséquences potentielles sur le transport en géométries plus complexes qui mériteraient une étude particulière
The question of transfer and spreading of living microorganisms, such as motile bacteria, is of interest in biology and ecology, but also in engineering and medicine.The way in which the background flow affects the behavior of these bacteria and how it impacts the bacterial transport through complex systems and on the macroscopic properties of the fluid remains unclear and little studied.In this thesis, I present an experimental investigation of the coupling between the local bacteria-driven motion and the fluid advection.In a first part, I investigate the rheological response of E. coli suspensions when subjected to weak flows (low shear rates). I show that, in particular conditions, the microscopic perturbations caused by the bacteria highly impact on the macroscopic viscosity of the suspension, leading to a striking viscosity decrease and eventually overcoming the dissipative effects due to viscous loss. I also identify the relevant time scales defining this viscosity decrease.In a second part, I perform experiments in a capillary channel and analyze the coupling for stronger flows (higher shear rates), at which bacteria were found not to impact on the macroscopic viscosity. Instead, by analyzing the bacterial trajectories under flow, I evidence a breakage of the symmetry of this trajectories which, characterized by a preferential migration, causes the localization of the bacteria in a layer that extends over a significant distance from the surface, and thus potentially influencing the bacterial transport in complex systems

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Swiecki, Melissa K. "Bacillus anthracis spore-host interactions." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2007. http://www.mhsl.uab.edu/dt/2007p/swiecki.pdf.

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Hafizi, Fatima. "Characterization of the Interactions of the Bacterial Cell Division Regulator MinE." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23189.

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Symmetric cell division in gram-negative bacteria is essential for generating two equal-sized daughter cells, each containing cellular material crucial for growth and future replication. The Min system, comprised of proteins MinC, MinD and MinE, is particularly important for this process since its deletion leads to minicells incapable of further replication. This thesis focuses on the interactions involving MinE that are important for allowing cell division at the mid-cell and for directing the dynamic localization of MinD that is observed in vivo. Previous experiments have shown that the MinE protein contains an N-terminal region that is required to stimulate MinD-catalyzed ATP hydrolysis in the Min protein interaction cycle. However, MinD-binding residues in MinE identified by in vitro MinD ATPase assays were subsequently found to be buried in the hydrophobic dimeric interface in the MinE structure, raising the possibility that these residues are not directly involved in the interaction. To address this issue, the ability of N-terminal MinE peptides to stimulate MinD activity was studied to determine the role of these residues in MinD activation. Our results implied that MinE likely undergoes a change in conformation or oligomerization state before binding MinD. In addition we performed circular dichroism spectroscopy of MinE. The data suggest that direct interactions between MinE and the lipid membrane can lead to conformational changes in MinE. Using NMR spectroscopy in an attempt to observe this structure change, different membrane-mimetic environments were tested. However the results strongly suggest that structural studies on the membrane-bound state of MinE will pose significant challenges. Taken together, the results in this thesis open the door for further exploration of the interactions involving MinE in order to gain a better understanding of the dynamic localization patterns formed by these proteins in vivo.

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Sawyer, Elizabeth Bryony. "Biophysical analysis of haem-protein interactions in bacterial haem transfer systems." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611709.

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Harden, Mark Michael Jr. "Interactions between an integrative and conjugative element and its bacterial host." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130662.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, February, 2021
Cataloged from the official PDF of thesis.
Includes bibliographical references.
Conjugative elements are mobile genetic elements that can transfer from a donor bacterium to a recipient via an element-encoded type IV secretion system. Integrative and conjugative elements (ICEs) are an abundant class of conjugative element. ICEs are typically integrated into the bacterial host chromosome, but under certain conditions, or stochastically, they can excise from the chromosome and transfer to a recipient. ICEs likely interact with their bacterial host at every stage of their life cycle, but few of these interactions have been characterized. In this work I sought to 1) identify bacterial host factors necessary for efficient transfer of the integrative and conjugative element ICEBs1 to a recipient, and 2) determine whether the ICEBs1-encoded cell wall-modifying enzyme CwlT acts on the cell wall of the donor bacterium, the recipient bacterium, or both.
I used CRISPR interference to induce a knockdown of individual essential Bacillus subtilis genes, and then screened for gene knockdowns that caused an acute defect in transfer of ICEBs1. I found that wall teichoic acids were necessary in both ICEBs1 donors and recipients for efficient conjugative transfer. I found that depletion of wall teichoic acids caused cells involved in ICEBs1 conjugation to sustain lethal envelope damage caused by active conjugation machinery. Conjugative elements must bypass the cell wall of both the donor and recipient cells in a mating pair. Conjugative elements encode cell wall hydrolases that are required for efficient transfer, which are presumed to partly degrade the cell wall of the donor bacterium during conjugation. In order to investigate the role of the ICEBs1-encoded cell wall hydrolase CwlT in conjugation, I generated cell wall-less (L-form) strains of B. subtilis which could donate or receive ICEBs1.
In the absence of either the donor or recipient cell wall, CwlT was dispensable for efficient transfer. This finding indicates that CwlT acts on both the donor and recipient cell wall in a mating pair.
by Mark Michael Harden, Jr.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Biology

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39

Hoffman, Michele Therese. "Bacterial Endosymbionts of Endophytic Fungi: Diversity, Phylogenetic Structure, and Biotic Interactions." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/196079.

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This dissertation comprises a series of studies designed to explore the associations between plants and the endophytic fungi they harbor in their above-ground tissues. By viewing endophyte diversity in ecologically and economically important hosts through the lenses of phylogenetic biology, microbiology, and biotechnology, this body of work links plant ecology with newly discovered symbiotic units comprised of endophytic fungi and the bacteria that inhabit them.This work begins with a large-scale survey of endophytic fungi from native and non-native Cupressaceae in Arizona and North Carolina. After isolating over 400 strains of endophytes, I inferred the evolutionary relationships among these fungi using both Bayesian and parsimony analyses. In addition to showing that native and introduced plants contained different endophytes, I found that the endophytes themselves harbor additional microbial symbionts, recovering members of the beta- and gamma-proteobacterial orders Burkholderiales, Xanthomonadales, and Enterobacteriales and numerous novel, previously uncultured bacteria. This work finds that phylogenetically diverse bacterial endosymbionts occur within living hyphae of multiple major lineages of ascomycetous endophytes.A focus on 29 fungal/bacterial associations revealed that bacterial and fungal phylogenies are incongruent with each other and did not reflect the phylogenetic relationships of host plants. Instead, both endophyte and bacterial assemblages were strongly structured by geography, consistent with local horizontal transmission. Endophytes could be cured of their bacterial endosymbionts using antibiotics, providing a tractable experimental system for comparisons of growth and metabolite production under varying conditions. Studies of seven focal fungal/bacterial pairs showed that bacteria could significantly alter growth of fungi at different nutrient and temperature levels in vitro, and that different members of the same bacterial lineages interact with different fungi in different ways.Focusing on one isolate, I then describe for the first time the production of indole-3-acetic acid (IAA) by a non-pathogenic, foliar endophytic fungus (Pestalotiopsis neglecta), suggesting a potential benefit to the host plant harboring this fungus. I show that this fungus is inhabited by an endohyphal bacterium (Luteibacter sp.) and demonstrate that mycelium containing this bacterium produces significantly more IAA in vitro than the fungus alone. I predict that the general biochemical pathway used by the fungal-endohyphal complex is L-tryptophan-dependent and measure effects of IAA production in vivo, focusing on root and shoot growth in tomato seedlings.

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Fox, Sean J. "Identification and Characterization of Genetic Factors Involved in Candida-Bacterial Interactions." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etd/2277.

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Throughout existence, fungi and bacteria have long shared ecological niches and thus engage in numerous interactions to mutually enhance survival or antagonistically gain competitive advantages. Of importance to human health are those interactions that involve bacteria with the opportunistic fungi, Candida albicans. An important virulence factor of C. albicans is the ability to control morphology, which allows the transition between yeast, pseudohyphal, and hyphal phenotypes. Morphological control in C. albicans is governed by quorum sensing and the secreted autoregulatory molecule farnesol. Quorum sensing allows individual cells to sense the environment and respond as a group. Bacteria also use quorum sensing to communicate and control virulence. Despite their abundance in nature, very little is known about the interactions of C. albicans with bacteria on a genetic and molecular level. The objective of our research is to identify the genetic elements involved in C. albicans-bacterial interactions and characterize the genes that may participate in these relationships. To accomplish this, we screened a C. albicans mutant library for the ability to filament in the presence of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, where 3 typically, these three bacterial species inhibit C. albicans filamentation. We identified 836 C. albicans mutants that displayed a filamentous phenotype in the presence of bacteria. Collectively, 295 of these mutants filamented in the presence of all 3 bacterial species. Candidates were subsequently sequenced to identify the location of the mutation and the affected genetic element. CDR4, a putative ABC transporter, and ALS6, a putative adhesion, were further characterized for their specific involvement in Candida-bacterial interactions. Using a filamentation assay, cdr4 and als6 deletion strains demonstrated a decreased response to the inhibitory effects of farnesol, as well as bacterial molecules known to inhibit the production of hyphal-filaments. Additionally, the ability of cdr4 and als6 deletion strains to attach and form biofilms was significantly enhanced even in the presence of farnesol and bacterial inhibitors. The results of this study contribute to the body of knowledge involving polymicrobial interactions and these findings may lead to new antifungal targets for therapeutic interventions.

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Tujulin, Eva. "Host interactions of the intracellular bacterium Coxiella burnetii : internalisation, induction of bacterial proteins and host response upon infection /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5425-5.pdf.

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Hebert, Kathryn S. "Investigation of Anaplasma phagocytophilum and Anaplasma marginale adhesin-host cell interactions." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4130.

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Anaplasma phagocytophilum and A. marginale are the etiologic agents of bovine anaplasmosis and human granulocytic anaplasmosis, respectively. As obligate intracellular pathogens, binding and entry of host cells is a prerequisite for survival. The molecular events associated with these processes are poorly understood. Identifying the adhesins mediating binding, delineating their key functional domains, and determining the molecular determinants to which they bind not only benefits better understanding of Anaplasma spp. pathobiology, but could also benefit the development of novel approaches for protecting against infection. We previously demonstrated that A. phagocytophilum outer membrane protein A (ApOmpA) is critical for bacterial binding and entry host through recognition of α2,3-sialic acid and α1,3-fucose of its receptors, including 6-sulfo-sLex. In this study, we determined that two amino acids, G61 and K64, within its binding domain (ApOmpA59-74), are essential for ApOmpA function. We also confirmed the ability of ApOmpA to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. We next extended our studies to A. marginale as it also expresses OmpA (AmOmpA) and its role in infection has not been studied. Molecular models of ApOmpA and AmOmpA were nearly identical, especially in the ApOmpA binding domain and its counterpart in AmOmpA. Antisera raised against AmOmpA or its putative binding domain inhibit A. marginale infection. AmOmpA G55 and K58 are contributory and K59 is essential for AmOmpA to bind to host cells. AmOmpA binding is dependent on α2,3-sialic acid and α1,3-fucose. Coating inert beads with AmOmpA conferred the ability to bind to and be taken up by host cells, confirming that it acts as an adhesin and invasin. 6-sulfo-sLex is dispensable for AmOmpA binding and A. marginale infection. ApOmpA works cooperatively with Asp14 (14-kDa A. phagocytophilum surface protein) to promote optimal infection of host cells. We found that Asp14 is conserved across A. phagocytophilum strains and in A. marginale and confirmed the ability of Asp14 to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. Collectively, this work advances our understanding of A. phagocytophilum and A. marginale adhesion and invasion of host cells.

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Li, Xinyan. "Interplay between bacterial virulence and plant innate immunity in Ppseudomonas-arabidopsis interactions." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/243.

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Artursson, Veronica. "Bacterial-fungal interactions highlighted using microbiomics : potential application for plant growth enhancement /." Uppsala : Dept. of Microbiology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005127.pdf.

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45

Levenson, Robert Herman. "Insights into Protein-Protein Interactions within the Bacterial Flagellar Motor C-Ring." Thesis, University of California, Santa Barbara, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3618776.

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The cytoplasmic ring (C-ring) of the flagellar motor consists of three proteins: FliG, FliM, and FliN, each present in different copy numbers. These proteins perform the function of transmitting torque from the stators to the basal body, as well as regulating the rotational direction of the flagellum. Despite decades of study and great progress towards the understanding of the molecular details of the flagellum’s mode of action, substantial questions still remain about its detailed architecture and molecular mechanisms. Here we describe a series of in vitro and in vivo experiments designed to provide insight into the structure of the flagellar C-ring.

We begin this work by presenting a background of the forms of cellular motility and provide context for the flagellum within the great diversity of motility mechanisms. We then summarize the bacterial chemotaxis signal transduction system, one of the most deeply characterized signaling pathways within biology. Lastly we introduce the flagellum with a focus on C-ring structure and function.

The research portion begins with a characterization of the interaction between the FliG N-terminal domain (FliG_N) and the C-terminal region of the flagellar membrane protein FliF (FliF_C). We find that these two proteins interact strongly and that this interaction causes widespread conformational changes throughout FliG_N. Based on NMR and other biophysical data we propose a binding site for FliF_C centered on helix 1 of FliG_N.

In the next section we further characterize the interaction between FliF_C and FliG_N. We generate a fusion FliF_C-FliG_N polypeptide and characterize this complex. Using spin labeling experiments we confirm our predicted interaction site between FliF_C and FliG_N. We also identify a novel interaction between an important hydrophobic patch on the FliG_NM linker and FliG_N.

Next we study and characterize the domain architecture of the full-length FliG_NMC protein. By evaluating pair-wise domain interactions and comparing NMR spectra of numerous FliG constructs, in combination with in vivo experiments, we provide evidence that the FliG middle- (FliG_M) and C-terminal (FliG_C) domains interact in an intra-protomer manner. This model is in excellent accord with the 3D structure of the Salmonella typhimurium C-ring as derived from cryo-EM.

Lastly, we describe a number of experiments probing complex formation between FliG, FliM and FliN, with the aim of determining how these interactions are modulated by CheY binding.

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Matos, Renata Filipa Cruz de. "Enterococcus faecalis V583 prophages: Dynamic interactions and contribution to bacterial pathogenic traits." Doctoral thesis, Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica, 2013. http://hdl.handle.net/10362/10882.

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Dissertation presented to obtain the Ph.D degree in Biology.
Enterococcus faecalis is a firmicute of the human gastrointestinal tract (GIT) core-microbiome. This commensal bacterium is one of the first to colonize the GIT of humans after birth and remains associated with the adult human gut microbiota at sub-dominant levels. Although harmless, certain strains can become pathogenic in immune-compromised and elderly patients causing urinary tract infections, bacteremia and infective endocarditis. This bacterial species has been recognized as an opportunistic pathogen for several decades, and now ranks as a major cause of hospital-acquired infections worldwide.(...)

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Foster, Dylan, Gethien Andrew, and Sean Fox. "Developing a C. elegans Co-infection Model for Assessing Bacterial-Fungal Interactions." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/128.

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The Candida genus is full of fungi that are subtle parts of the human microbiome, but they can cause complications if they overgrow within the body—specifically the mouth and throat, the genitalia, and the entire body through infection of the bloodstream. Candida species are a rising problem for many across the world, and this can be seen in the recent threat of Candida auris hospitalizing patients and being regularly resistant to anti-fungal medications. Beyond C. auris, Candida albicans is the most common Candida species that humans must combat because it causes the most infections in humans—mostly vaginal yeast infections. C. albicans does have natural competitors that can either inhibit its growth or kill it in general, and the competition that we took advantage of was with the Alcaligenes species. Alcaligenes faecalis and Alcaligenes viscolactis have been shown to at least inhibit C. albicans growth and maybe even kill the fungus. This rate of infection from C. albicans places it at the forefront of Candida research, and we attempted to further this research by utilizing both A. faecalis and A. viscolactis to create a co-infection model for Caenorhabditis elegans—a simple nematode lifeform. It is known that A. faecalis and A. viscolactis do not commonly adversely affect humans, so little research has been done concerning their clinical effects. We were looking to find a possible answer to C. albicans infections beyond antifungal drugs because we know that antibiotic resistance is on the rise. We performed liquid assays to test the survivability of C. elegans nematodes in various bacterial/fungal circumstances. We subjected batches of C. elegans to E. coli OP50 as a control, A. faecalis, A. viscolactis, C. albicans, A. faecalis and C. albicans, and A. viscolactis and C. albicans. This procedure was followed in order to determine the viability of using the Alcaligenes species to either help the C. elegans survive the infection or prevent them from getting infected at all. After following through with the project, we found that there was a noticeable increase in the survivability of C. elegans when subjected to both one of the Alcaligenes species and C. albicans as opposed to the C. albicans alone. The data, although early, shows the possibility of Alcaligenes species being used to combat C. albicans infections in lifeforms.

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Matthews, Chad Robert. "Host Bacterial Interactions During Early Plaque Formation in Current and Never Smokers." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274112198.

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Baldock, Christopher Mark. "A Computational and Experimental Characterisation of Bacterial Interactions in the Plant Microbiome." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/24548.

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Microbiome manipulation provides opportunity to make crop production more efficient. For effective manipulation of bacterial communities, we need to understand the drivers of their variation. Bacterial interactions are one potential source, however, elucidating interactions is challenging due to experimental and statistical constraints. The aim of this thesis was to address these limitations and investigate the impact of bacterial interactions on plant microbiome dynamics. Three lines of questioning were pursued to address this: do interactions contribute to bacterial dynamics and are dynamics universal? What are key taxa important to said dynamics? Can interactions be studied in a mesocosm system? It was demonstrated that universal dynamics exist in most systems studied even after accounting for experimental and technical confounders, establishing the importance of bacterial interactions to plant microbiome dynamics. A set of 19 bacterial families from the proteobacteria, actinobacteria and bacteroidetes were found to disproportionately interact with other taxa in the root and leaf microbiome. Root communities were more amendable to transplantation than those from leaves, with latter suffering high levels other contamination. A refined experimental system to minimize environmental contamination was devised and yielded improved results. Transplantation experimental data was used to estimate the dynamics of communities using multiple statistical techniques. A sequence variant from the genus Sphingomonas as well as members of the Rhizobiales were responsible for most interactions. In sum, interactions contribute to bacterial dynamics in most cases, a set of bacterial families disproportionately affect these dynamics, and root communities are amendable to transplant to investigate their dynamics and potential interactions. This thesis highlights that interactions should be considered for the effective design of microbiome engineering technologies in agriculture.

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Karimpour-Fard, Anis. "Prediction of protein-protein interactions and function in bacteria /." Connect to full text via ProQuest. Limited to UCD Anschutz Medical Campus, 2008.

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Thesis (Ph.D. in Bioinformatics) -- University of Colorado Denver, 2008.
Typescript. Includes bibliographical references (leaves 141-150). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;

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Dissertations / Theses on the topic 'Bacterial Interactions'

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