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Maraha, Ninwe. "Physiological status of bacteria used for environmental applications /". Stockholm, 2007. http://diss.kib.ki.se/2007/91-7357-063-X/.
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Jernberg, Cecilia. "Use of microbiomics to study human impacts on complex microbial communities /". Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-960-2/.
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Duvernoy, Marie-Cécilia. "Mécanique de croissance d'une micro-colonie bactérienne". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY074/document.
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Ce travail nous a permis de proposer un cadre pour sonder la morphogenèse d'une micro-colonie bidimensionnelle. Plus particulièrement, nous avons exploré la manière dont les effets individuels de croissance et d'adhésion se combinaient au cours de la croissance de la micro-colonie. Nous avons montré (i) que l'adhésion de cellules isolées est asymétrique du fait d'un vieux pôle plus ancré et (ii) que l'allongement des bactéries peut induire des forces de poussée à l'intérieur des colonies. Dans la mesure où ces deux effets, combinés à l'échelle d'une micro-colonie, sont susceptibles de générer des contraintes mécaniques, nous avons développé une technique pour mesurer les forces d'adhésion résultantes à l'aide de substrats déformables. Nous avons ainsi démontré que des adhésions focales sont créées et rompues dynamiquement, avec un biais au vieux pôle des cellules. Nous avons aussi examiné le rôle de l'adhésion sur la forme des colonies. Nous avons montré que l'adhésion polaire était responsable de la transition d'un régime de croissance linéaire à un régime bidimensionnel qui est observée après la première division. Pour des colonies de taille plus importante, le niveau d'adhésion était aussi corrélé avec la forme globale des colonies. Enfin, l'adhésion est aussi impliquée dans la transition d'une colonie bidimensionnelle à une colonie tridimensionnelle. L'ensemble de ces résultats suggère que l'expression des adhésines ainsi que leur localisation à la surface des cellules pourraient permettre aux bactéries de moduler activement la forme du groupe dans lequel elles viventIn this work, we propose a framework to understand the morphogenesis of two-dimensional microcolonies. In particular, we have explored how growth and adhesion of individual cells compete during microcolony extension. We have shown (i) that isolated cells display an asymmetry in their adhesion, which is higher at the old pole, (ii) that bacterial elongation can result in pushing forces inside the colony. Since the combination of these two effects is expected to produce mechanical stress at the scale of the microcolony, we have developed a method to measure the resulting adhesion forces using deformable substrates. We have demonstrated that focal adhesions are dynamically established and ruptured, with a bias towards the old poles. We have also probed the role of adhesion in the shape of the colony. We have shown that polar adhesion drives the transition from a linear to a two-dimensional growth after the first division. At larger colony sizes, the level of adhesion continues to correlate with the global shape of the colony. Finally, adhesion is involved in the transition from a two-dimensional to a three-dimensional colony. Taken together, our results suggest that the expression of adhesins and their location at the surface of the cells could be levers by which bacteria actively modulate the shape of the group in which they reside
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Frühauf, Patrik. "Zařízení vzduchotechniky a kvalita vzduchu v budovách". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227751.
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This thesis deals with the relationship between HVAC systems and internal microclimate of buildings. The work discusses briefly about different components which are formulating internal microclimate. More details are then focused on the issue of microbial microclimate.
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Alfiniyah, Cicik. "The role of quorum sensing in bacterial colony dynamics". Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/19542/.
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The quorum sensing (QS) signalling system allows colonies of bacteria to coordinate gene expression to optimise behaviour at low and high cell densities, giving rise to individual and group responses, respectively. The main aim of this thesis is to understand better the important roles of QS in bacterial colony dynamics. Thus a mathematical description was developed to thoroughly explore key mechanisms and parameter sensitivity. The nature of the QS system depends very much on the species. Pseudomonas aeruginosa was chosen as a model species for this study. P. aeruginosa is a Gram-negative bacterium that is responsible for a wide range of chronic infections in humans. Its QS signalling system is known to involve the las, rhl and pqs systems; this thesis focuses on the first two. The las system includes the LasR regulator and LasI synthase, which direct the synthesis of autoinducer 3O-C12-HSL. Similarly, the rhl system consists of the RhlR regulator and RhlI synthase, directing the synthesis of autoinducer C4-HSL. The mathematical model of the las system displays hysteresis phenomena and excitable dynamics. In essence, the system can have two stable steady states reflecting low and high signal molecule production, separated by one unstable steady state. This feature of the las system can give rise to excitable pulse generation with important downstream impact on the rhl system. The las system is coupled to the rhl system in two ways. First, LasR and 3O-C12-HSL activate the expression of their counterpart in the rhl system. Second, 3O-C12-HSL blocks activation of RhlR by C4-HSL. Furthermore, the las-rhl interaction provides a `quorum memory' that allows cells to trigger rhamnolipid production when they are at the edge of colony. It was demonstrated how the dynamical QS system in individual cells and with coupling between cells can affect the dynamics of the bacterial colony.
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Maroto, Fernández Enric. "Image analysis of bacterial colonies in classic and alternative gel-based growth media". Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/666842.
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La adopción de tecnologías automatizadas de análisis de imagen va en aumento en los laboratorios de microbiología, éstas suponen un medio para incrementar la productividad, la objetividad y la trazabilidad de los resultados de las pruebas. Específicamente, la enumeración de colonias y la detección del desarrollo de color en éstas constituyen las dos aplicaciones más comunes de la visión artificial en el laboratorio microbiológico. En el albor de la era de la visión computarizada, el contaje y análisis de colonias se posiciona como una tarea más que automatizar mediante la inteligencia artificial aplicada al análisis de imagen.
La presente tesis evalúa la capacidad de los escáneres flatbed para capturar imágenes para la detección y medida del desarrollo de color en colonias. Así mismo, se evalúa la incidencia que distintas concentraciones de cromógenos tienen sobre el desarrollo de color a lo largo del tiempo. Se sugieren aproximaciones asequibles para interpretar los datos obtenidos y se profundiza en el análisis del desarrollo de color. Los aspectos metrológicos de la técnica presentada son debidamente abordados. Se presta particular atención a la caracterización de la técnica empleada, a resaltar sus limitaciones y a evaluar la reproducibilidad de los resultados obtenidos en distintos dispositivos.
Se aportan los primeros datos en relación a la enumeración de colonias aplicando técnicas cinéticas de toma de imagen en medios de cultivo alternativos. Así mismo, se evalúa el tiempo hasta detección de las colonias, junto con la recuperación de estas como medios para estudiar la inducción de estrés vinculada a la presencia de matrices potencialmente tóxicas.Microbiology laboratories are increasingly adopting automated imaging technologies as means to leverage their productivity and increase traceability and objectivity of test results. Specifically, colony enumeration and detection of color development in these stand as the two most common applications of machine vision in microbiology laboratories. In the advent of the age of computer vision, colony counting and analysis stands as yet another process that can be automated by means of image-driven artificial intelligence. The present work assesses the capacity of flatbed scanners to capture images for the detection and measurement of color development in colonies. Effects of different concentrations of chromogens and the differences in color development over time are evaluated. Affordable approaches to interpret derived data are suggested and insights related to the analysis of color development are supplied. Metrological aspects of the measurement technique are duly addressed. Thus, particular care is devoted to characterize the measurement technique employed, to highlight its limitations, and to assess the cross-device reproducibility of obtained results. First-in-class accounts of enumeration of colonies in alternative culture media, based on kinetic imaging of their growth, are also reported. Furthermore, time to the earliest detection of colonies is evaluated, along with colony recovery evaluation, as a means to assess stress induction related to the presence of potentially toxic matrices.
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Daniel, Scott Garrett, i Scott Garrett Daniel. "Gut Bacterial Dysfunction in TGFβ Deficient Colon Cancer". Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625592.
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Colorectal cancer (CRC) has a 5-year survival rate of 68% yet it still has a mortality rate of 50,000 per year. While CRC has a host of causes, one that stands out is TGFβ deficient signaling, which is disrupted in a majority of high-microsatellite-instability or inflammation-associated CRCs. Since TGFβ is a multifunctional cytokine, it has been elusive to determine whether its effect on cancer development is operating through inflammation, differentiation or developmental pathways. Additionally, it is now becoming apparent that a great number of CRC cases can be associated with and possibly caused by gut bacteria dysbiosis. Here, I present a metagenomic and metatranscriptomic study of the interactions between TGFβ deficient signaling, inflammatory signaling, and the microbiome in a CRC mouse model. TGFβ deficient mice have reduced amounts of Firmicutes as well as mRNA counts of a key butyrate enzyme. Lack of butyrate, as shown by previous literature, could be inhibiting apoptosis and promoting growth. Also, TGFβ deficient mice have increased mRNA counts of polyamine producing genes, which could act synergistically with butyrate reduction. I find that H. hepaticus inoculation, as a source of inflammatory signaling, affects another species, M. schaedleri, to produce pro- inflammatory lipopolysaccharides. Additionally, H. hepaticus itself has increased oxidative phosphorylation; reactive oxygen species from this process could be adding to cancer-promoting DNA damage. Taken together, TGFβ deficient signaling and H. hepaticus inoculation, disrupt enough pathways to cross the threshold of carcinogenicity in 40% of the mice in our study. The results of this study emphasize the importance of
microbiome function and represent possible new avenues of treatment.
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Frankenfeld, Cara L. "Hormone status postmenopause : colonic bacterial effects /". Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10854.
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Degnan, B. A. "Transport and metabolism of carbohydrates by anaerobic gut bacteria". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282017.
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Bridson, Eric Youlden. "Quantal microbiology". Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312059.
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Wang, Xin. "Comparative aspects of carbohydrate fermentation by colonic bacteria". Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335223.
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Smith, Elizabeth Anne. "Dissimilatory amino acid metabolism by human colonic bacteria". Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627591.
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Bragger, Janine Lesley. "The design of drug delivery systems for the colon". Thesis, King's College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307587.
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Willis, Caroline. "The physiology and ecology of sulphate-reducing bacteria in the human colon". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439156.
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Amansec, Sarah Gracielle Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "Role of resistant starch and probiotics in colon inflammation". Awarded by:University of New South Wales. School of Biotechnology and Biomolecular Sciences, 2005. http://handle.unsw.edu.au/1959.4/23041.
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An imbalance of the T cell immune response is observed in inflammatory bowel disease. Intestinal microbes have been linked to the disease and the disease process leads to severe mucosal injury and systemic translocation of bacterial products. Aminosalicylates, corticosteroids and immunomodulators reduce these aggressive activities but are associated with potentially serious adverse events. The aim of this work was to investigate the effects of administration of prebiotics and probiotics that modulate the gut microflora and modulate the immune response, in ameliorating severity of colitis. The prebiotic, high amylose maize resistant starch was used at two different concentrations. A number of Bifidobacterium and Lactobacillus strains were used as probiotics. BALB/c mice were administered the prebiotics and probiotics and intrarectally infused with 2.5 mg trinitrobenzene sulfonic acid (TNBS) in 45% ethanol, thereby generating colitis. Mucosal cytokine responses, colonic microbial profiles and disease activity indices were monitored. The 5% concentration of high amylose maize resistant starch delayed progression of TNBS colitis as evidenced by reduced weight loss, lesser tissue damage, abrogation of the expression and synthesis of IFN-?? and upregulation of IL-4 and IL-10. The 30% concentration of high amylose maize resistant starch exacerbated the inflammatory response with an increase in acetic acid, coliforms and endopores in the colonic contents. Three strains of bifidobacteria and 3 strains of lactobacilli were individually screened for their activity against TNBS colitis. Each strain had a distinctive effect on the course of colon inflammation. Lactobacillus fermentum VRI 003 was selected for further study as it provided most protection. The ratio of immunosuppressive cytokines to pro-inflammatory cytokines was restored closer to the normal T cell cytokine levels. It also reduced the incidence of translocation of enteric bacteria into the spleens. Dosing a minimum daily dose of 6x109 CFU L. fermentum VRI-003 to ulcerative colitis patients in remission and maintained on standard therapy for 6 months prevented the exacerbation of symptoms, including diarrhea and abdominal pain, and improved the patient general well being. It also suppressed production of IFN-?? and sustained IL-10 levels. Moreover, absence of endospores and lower numbers of coliforms were detected in the faeces of UC patients during L. fermentum VRI-003 treatment. In summary, 5% high amylose maize resistant starch and L. fermentum VRI 003 prevented colon inflammation by changing the nature of the T cell immune response and modifying the colonic microflora in the murine model. The clinical evidence supported these findings.
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Vulevic, Jelena. "Production of 1,2-SN-Diacylglycerol by human faecal bacteria : implication for colon cancer". Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272248.
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Duncan, A. J. "An in vitro study of the interactions of bacteria from the human colon". Thesis, Robert Gordon University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373776.
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Nettles, Rachel Marie. "Bacterial Community Ecology of the Colon in Mus musculus". BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6912.
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The gut microbiome is a community of closely interacting microbes living in the gastrointestinal tract. Its structure has direct relevance to health. Disturbances to the microbiome, such as due to antibiotic use, have been implicated in various diseases. The goal of this study was to determine how the gut microbiome reacts to and recovers from disturbance caused by antibiotics. Because diet also influences the microbiome, this study included the interaction between diet and antibiotics. Half of the mice in each diet treatment were given antibiotics to disturb their microbiomes. After cessation of antibiotics, mice were paired in combinations within diets to determine whether the microbiomes of control mice influenced the disturbed microbiomes of formerly antibiotic mice. Chapter 1. Diet significantly altered the structure of the gut microbiome but its effect was significantly smaller than the effect of antibiotics. There was a significant interaction between diet and antibiotics; the antibiotic effect was larger in the cornstarch diet than in the glucose diet. Dysbiotic microbiomes resulting from antibiotics were characterized by an increase in Bacteroidetes and Proteobacteria, and a decrease in Firmicutes. Antibiotic administration also resulted in an initial increase OTU diversity, mainly because it reduced the abundance of dominant OTUs, resulting in greater evenness. Chapter 2. Seven weeks after the cessation of antibiotics (experiment termination), the effect of the antibiotics on the microbiome was still evident. The structure of the dysbiotic microbiome had not returned to that of control mice. Antibiotics significantly increased the relative abundance of some taxa and significant decreased the relative abundance of others. It was unexpected that the taxonomic hierarchy within the microbiome did not recover after 7 weeks following cessation of antibiotics. It would appear, therefore, that antibiotics established a new, semi-stable hierarchy. Chapter 3. When paired together, the assumption was that dysbiotic microbiomes of antibiotic mice would be positively influenced by microbiomes of control mice, based on the assumption that the control mouse would act as a probiotic for the antibiotic mouse, either via coprophagy or consumption of food contaminated by feces. Contrary to that hypothesis, the microbiomes of control mice became more similar to that of antibiotic mice. One can offer at least two hypotheses to explain this result, but neither was tested. First, compared to the control microbiome, the dysbiotic microbiome may have been more stable and thus more resistant to change due to invasion by OTUs from the control microbiome. Other research has shown that dysbiotic microbiomes have a high degree of stability. If this were true, the use of probiotics is questionable. Second, one or more of the antibiotics could still have been active at the initial phase of pairing, and coprophagy caused the microbiome of the control mice to rapidly become dysbiotic. If this is true, the experiment should have been conducted with a waiting period between the cessation of antibiotic administration and pairing.
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Beltinger, Johannes Hermann. "Studies on colonic epithelial ion transport and barrier function". Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311747.
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Zhao, Ling. "Increased bile acid-metabolizing bacteria contributes to enhanced gastrointestinal motility in irritable bowel syndrome". HKBU Institutional Repository, 2018. https://repository.hkbu.edu.hk/etd_oa/561.
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Irritable bowel syndrome (IBS), majorly characterized by irregular bowel movements and abdominal pain, is one of the most prevalent functional gastrointestinal disorders (FGIDs) in the world. Disturbance of gut microbiota, closely linking with gut dysfunction, has been regarded as one of important pathogenetic factors for IBS. However, gut microbiota-driven mechanism underlying IBS remains unclear, which leads to inefficient and non-specific effects of current microbiota-oriented therapy. In this thesis, function-based microbiota investigation with combination of metagenomic and metabolomic analyses was separately performed in IBS cohort and model to precisely link pathogenic species with disordered GI motor function. A series of microbiota manipulation studies in rodents were conducted to explore bacteria-driven molecular mechanism. Firstly, a pilot study with 'omics' analyses revealed fecal microbial structure significantly varied in IBS patients with disorder GI motility relative to healthy controls (HC). Such changed IBS enterotype was functionally characterized by disturbed metabolism of bile acids (BAs) that are previously proved to regulate GI motor function. It indicates microbiota-driven GI dysmotility relevant to disturbance of BA metabolism in IBS. Secondly, a systematic review with meta-analysis was performed to comprehensively understand existing findings related to BA metabolism and its linkage with IBS. Results showed that abnormal BA excretion, previously reported in at least one IBS subtype, is associated with dysregulation of BA synthesis, marked with abnormalities of circulating indices 7α-hydroxy-4-cholesten-3-one (C4) and fibroblast growth factor 19 (FGF19). However, what's the role of gut microbiota in abnormal BA excretion is undetermined. Thirdly, to explore possible role of gut microbiota in abnormal BA excretion in IBS, BA metabolites and BA-related microbiome were simultaneously analyzed in stools of recruited subjects. Results found that total BA and microbiota-derived BAs were remarkably elevated in a quarter of IBS-D patients (BA+IBS-D) who exhibited more frequent defecation, higher level of serum C4 but lower level of serum FGF19 than those with normal BA excretion (BA-IBS-D). In line with metabolic results, abundances of BA-metabolizing bacteria, particularly Clostridium scindens (C. scindens) simultaneously expressed hdhA and bais that are responsible for BA 7α oxidation and dehydroxylation, were highly enriched in fecal metagenomes of such particular IBS-D population. These findings suggest the increased BA-metabolizing microbiome is associated with the dysregulated host BA synthesis in the subgroup of BA+IBS-D patients. Fourthly, by analyzing metabolites and bacteria related to BA metabolism, a neonatal maternal separation (NMS)-induced IBS-D rat model characterized by accelerated GI motility and excessive BA excretion were found to largely mimic gut microbial BA metabolism in BA+IBS-D patients. Specifically, intraluminal total and secondary BAs were significantly elevated in the large intestinal lumens (cecum, proximal colon and feces) of NMS rats, together with increased abundances of hdhA- and bais-expressing Clostridium species, including C. scindens. Moreover, quantitative polymerase chain reaction (PCR) analysis showed upregulated mRNA expression of cholesterol 7 α-hydroxylase (CYP7A1) whereas downregulated mRNA expression of small heterodimer partner (SHP) in the liver of NMS rats, indicating enhanced hepatic BA synthetic level. These observations based on such IBS-D model suggest the association of excessive BA-metabolizing microbiome and increased hepatic BA synthesis. Fifthly, to further clarify whether excessive BA-metabolizing bacteria contribute to enhanced hepatic BA synthesis and to explore the underlying molecular mechanism, we performed bacterial intervention in pseudo germ-free (GF) or/and specific pathogen free (SPF) mice by transplantation of human fecal microbiota and the signal strain C. scindens. Compared with GF mouse recipients of HC and BA-IBS-D fecal microbiota, BA+IBS-D fecal microbial recipients displayed shorter GI transit and increased subsistence of C. scindens in the cecal contents. In line with higher level of serum C4, taurine-conjugated BA contents and mRNA expressions of BA synthetase CYP7A1 and sterol 12α-hydroxylase (CYP8B1) were significantly elevated in the liver of BA+IBS-D recipients. These findings showed bioactive effects of BA+IBS-D fecal microbiota with enrichment of C. scindens on hepatic BA synthesis. Next, to further confirm the effects of the species C. scindens on host BA synthesis, we individually colonized C. scindens strains (ATCC 37504) to pseudo GF and SPF mice. Results showed both mice models with single strain colonization exhibited accelerated GI transit and higher contents of hepatic total and taurine-conjugated BAs compared with individual vehicles treated with PBS. Combining metabolic changes, the upregulated expressions of hepatic CYP7A1 mRNA in colonized mice indicate that C. scindens substantially promote hepatic BA synthesis in colonized mice. Furthermore, contents of taurine-conjugated BAs, served as natural antagonists of farnesoid X receptor (FXR) that negatively control of new BA synthesis, were elevated in ileal lumens of colonized mice. Expressions of FXR-targeted genes SHP and fibroblast growth factor 15 (FGF15) were consistently reduced in the liver and ileum tissues of colonized mice, respectively. Results suggest that suppression of FXR-mediated feedback signaling is involved in Clostridium-driven hepatic BA oversynthesis, which deserve the further investigation. Collectively, the works of this thesis integrating clinical and animal studies indicate that BA-metabolizing bacteria, particularly C. scindens, enhance hepatic BA synthesis and consequently leads to BA overexcretion. It provides novel bacteria-driven mechanism for enhanced GI motility, and supply a direction in precise microbiota-related pathogenesis and medication for IBS-D population in future.
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Pränting, Maria. "Bacterial Resistance to Antimicrobial Peptides : Rates, Mechanisms and Fitness Effects". Doctoral thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-130168.
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The rapid emergence of bacterial resistance to antibiotics has necessitated the development of alternative treatment strategies. Antimicrobial peptides (AMPs) are important immune system components that kill microbes rapidly and have broad activity-spectra, making them promising leads for new pharmaceuticals. Although the need for novel antimicrobials is great, we also need a better understanding of the mechanisms underlying resistance development to enable design of more efficient drugs and reduce the rate of resistance development. The focus of this thesis has been to examine development of bacterial resistance to AMPs and the resulting effects on bacterial physiology. The major model organism used was Salmonella enterica variant Typhimurium LT2. In Paper I, we observed that bacteria resistant to PR-39 appeared at a high rate, and that the underlying sbmA resistance mutations were low cost or even cost-free. Such mutants are more likely to rapidly appear in a population and, most importantly, will not disappear easily once the selective pressure is removed. In paper II, we isolated protamine-resistant hem- and cydC-mutants that had reduced growth rates and were cross-resistant to several other antimicrobials. These mutants were small colony variants (SCVs), a phenotype often associated with persistent infections. One SCV with a hemC-mutation reverted to faster growth when evolved in the absence of protamine. In paper III, the mechanism behind this fitness compensation was determined, and was found to occur through hemC gene amplification and subsequent point mutations. The study provides a novel mechanism for reversion of the SCV-phenotype and further evidence that gene amplification is a common adaptive mechanism in bacteria. In Paper IV, the antibacterial properties of cyclotides, cyclic mini-proteins from plants, were evaluated. Cycloviolacin O2 from violets was found to be bactericidal against Gram-negative bacteria. Cyclotides are very stable molecules and may be potential starting points for development of peptide antibiotics.
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Parrett, Alison M. "Development of colonic fermentation in early life". Thesis, University of Glasgow, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390694.
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Charrier, Cédric. "Biochemistry and microbial ecology of butyrate formation in human colonic bacteria". Thesis, University of Aberdeen, 2006. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU207021.
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This work describes the identification and characterisation of a novel class of CoA-transferase involved in butyrate formation in human colonic bacteria. The CoA-transferase gene was identified form Roseburia sp. A2-183 and the gene product overexpressed in an E. coli lysates. The CoA-transferase has a broad pH optimum around neutral and shows activity with butyryl-CoA and to a lesser extent propionyl-CoA. Acetate, propionate, butyrate, isobutyrate and valerate but not 4-hydroxybutyrate, which is the preferred substrate of the closely related clostridial 4-hydroxybutyrate CoA-transferases, were used as co-substrate. The Km for butyryl-CoA and propionyl-CoA were similar but the maximal velocity of the enzyme in the presence of butyryl-CoA provided further evidence that the CoA-transferase from Roseburia sp. A2-183 is a butyryl-CoA CoA-transferase. Characterisation of the CoA-transferase substrate specificity from different butyrate-producing bacteria, including the lactate-utilising butyrate-producing Anaerostipes caccae L1-92 and Eubacterium hallii L2-7, as well as the clostridial cluster IV representative Faecalibacterium prausnitzii A2-165, indicated that the enzyme is the same in all these butyrate-producing bacteria. The metabolic cooperation between a lactic acid bacterium and the lactate-utilising butyrate-producing A. caccae L1-92 was investigated in vitro and in gnotobiotic rodents. Although the in vivo experiment failed to demonstrate the conversion of lactate to butyrate, metabolic analysis revealed significant amounts of butyrate in the caecum of di-associated animals and the establishment of a stable colonisation by the oxygen-sensitive A. caccae L1-92 represents nevertheless an essential step in assessing the potential of the butyrate-producing bacteria for probiotic application.
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Rumney, C. J. "An in vitro study of the metabolic activities of bacteria from the human colon". Thesis, Open University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234270.
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Costello, Amanda Jane. "Influence of substrate supply to the colon on bowel habit and the amount and composition of stool output". Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318219.
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Rodrigues, Pedro A. D. P., i Pedro A. D. P. Rodrigues. "Bacterial Symbionts at the Colony and Individual Levels: Integration through Behavior and Morphology in a Social Insect". Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621295.
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The determination of a symbiotic association as beneficial requires good assessment of the costs and benefits involved in the maintenance and transmission of these microbes across generations. In social insects, symbiotic associations are complex as they may involve a network of interactions between individual and colony that result in stable associations over evolutionary time. My goal was to investigate the roles of behavior and morphology as integrators that have enabled the benefits of harboring gut microbes to reach both adult and growing brood in a colony. To achieve this goal, I used turtle ants (Cephalotes), a group that has co-evolved with their gut microbes since the Eocene (Sanders et al. 2014) and that shows a variety of morphological and behavioral specializations likely connected to this symbiotic association. In my dissertation I present evidence that the specialized behavior and morphology of Cephalotes are indeed strongly associated with mechanisms that ensure stability of ant-gut microbe interactions over evolutionary time. In Appendix A, I show that a valve between the crop and midgut (proventriculus) of C. rohweri works as a filtration organ, capable of excluding possible pathogens from the mostly liquid diet consumed by turtle ants. In addition, the proventricular filter is also associated with the structuring of the gut microbiota, dividing it in at least two great groups: one upstream and another downstream of the proventriculus. Through behavioral observation and microscopy, we also suggest that the formation of the proventricular filter is only complete after young and sterile workers (callows) are inoculated with the core group of symbiotic bacteria. In Appendix B, I present results confirming that the compartmentalization of gut microbiota is also present in the congener C. varians. I compare these results with previously published data, defining the meta-communities of the gut microbiota, and demonstrate that the previously recognized core microbiota is composed of compartment-specific microbial communities and lineages. This compartmentalization of the gut microbiota is similar to the one found in highly specialized herbivores, both vertebrates and invertebrates. In addition, I also sampled the infrabuccal pocket, a characteristic oral cavity found in ants and that has largely been ignored in studies of gut symbiosis. Based on my results, I provide compelling evidence that hindgut microbes are inoculated into food particles trapped in the infrabuccal pocket, aiding in digestion of this substrate. Moreover, I suggest that trophallaxis olays a central role in inoculation of food and individuals, and might be responsible for the transmission of nutrients that are predicted to result from the gut bacteria metabolism. Finally, in Appendix C I characterize abdominal trophallaxis in C. rohweri to gain insight on its role in the context of symbiotic associations with gut microbes. I show that the hindgut contents, including bacteria, can be transmitted via abdominal trophallaxis. This interaction is found to occur between all combinations of major and minor workers, in addition to callows. The rate of solicitation of abdominal trophallaxis is higher when individuals are protein starved, indicating that hindgut content may also be nutritive. Using shotgun metagenomic data, we show that the microbiota present in the infrabuccal pocket (mostly hindgut bacteria) are indeed capable of re-utilizing nitrogen and synthesizing essential amino acids, in addition to breaking down plant material. We also report that oral trophallaxis is a possible route for transmission of crop-specific bacteria for callows, as this group has performed oral trophallaxis at a relatively higher rate than older workers. Put together, these results highlight the importance of nestmate interactions and gut morphology in the establishment and maintenance of symbiotic microbes in a social insect, introducing a new model for explaining the evolution and functioning of ant-gut microbe symbiosis.
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Thapa, Dinesh. "Studies on the influence of essential oils on human gut bacteria and colonic cells". Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=225962.
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The ability of essential oils (EO) to manipulate the intestinal microbiota may potentiate their application in food as nutraceutical and as prophylactic agents for colonic disease. Little is known about the influence of EO on gut bacteria, the mechanism of their antibacterial action and genotoxicity to the host. Here, the antibacterial activities of EO in pure and in a mixed faecal culture were investigated. These antibacterial activities were further studied to compare the selective nature of EO and their effects on membrane integrity. The growth of gut pathogens and commensals was inhibited in a dose-dependent manner in pure culture, with most of the pathogens, Escherichia coli O157:H7, Clostridium difficile, C. perfringens and Salmonella typhimurium are sensitive to nerolidol, thymol, eugenol and geraniol at a half maximal inhibitory concentration (IC50) of 50-500 ppm. These concentrations of EO and mainly nerolidol were also inhibitory to some gut commensals, in particular affecting Faecalibacterium prausnitzii adversely in pure culture. In contrast, in the mixed culture system beneficial groups of bacteria, including F. prausnitzii, as determined by qPCR of 16S rRNA genes were not affected. Thymol and geraniol at 500 ppm suppressed the growth of total bacteria, resulting in minimal fermentation. A lower dose of 100 ppm of EO compounds was effective in suppressing the pathogen, C. difficile with no concern for commensal bacteria or their fermentation products, acetate, propionate and butyrate. This study also discovered that the proteome of commensal, Faecalibacterium prausnitzii and pathogenic gut bacteria, Escherichia coli, in response to EO compounds are affected differently. Thymol and eugenol down-regulated virulence factors in E. coli. The tested EO compounds were not genotoxic in the comet assay at non-toxic doses. Differential effects of EO compounds on gut pathogens and commensals and their non-toxicity but geno-protective properties could be applicable in improving gut health in man.
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LECLERC, MARION. "Physiologie et metabolisme des bacteries acetogenes hydrogenotrophes isolees du colon humain". Paris 11, 1997. http://www.theses.fr/1997PA112018.
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L'acetogenese reductrice est un mecanisme de reutilisation de l'hydrogene particulierement actif chez les individus non-methanoexcreteurs. Une vingtaine de souches acetogenes ont ete isolees au laboratoire a partir de selles de ces sujets. Notre objectif a ete d'etudier la physiologie et le metabolisme de 4 de ces isolats, appartenant aux genres clostridium, ruminococcus, et streptococcus. Ces 4 souches sont capables de produire de l'acetate a partir de h#2/co#2 comme seule source d'energie. L'utilisation de la voie reductrice de l'acetogenese a ete demontree par l'incorporation de #1#3co#2 dans l'acetate. Le metabolisme autotrophe apparait module par la presence d'extrait de levure, de tryptone, ou de jus de rumen dans le milieu. Des mecanismes chimioosmotiques de generation d'atp semblent impliques lors de l'acetogenese chez toutes les especes. Ceux-ci seraient dependants du na#+ dans le cas de clostridium f5a15. Ces especes acetogenes sont egalement capables d'utiliser un grand nombre de substrats organiques, dont des composes aromatiques. L'utilisation des glucides par ces souches est caracterisee par une fermentation de type acide-mixte. En absence d'extrait de levure dans le milieu, une production accrue de metabolites reduits est observee lors de la fermentation du glucose. Les profils fermentaires varient egalement en fonction de la souche et du substrat consideres. Ainsi, la souche de streptococcus ne produit que du lactate par fermentation du glucose, alors que l'acetate est le produit majeur de fermentation du pyruvate. La presence simultanee de glucose et de h#2/co#2 se traduit par une croissance mixotrophe de la souche de ruminococcus. L'utilisation simultanee de ces substrats par les clostridium ne s'effectue que lorsque le glucose atteint une concentration seuil. La souche de streptococcus montre une croissance mixotrophe ou diauxique en presence des deux substrats, selon la nature de la source d'energie utilisee pour la preculture. La voie de l'acetogenese reductrice apparait ainsi inactive chez cette espece, lorsqu'elle est precultivee avec le glucose.
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Barcenilla, Adela. "Diversity of the butyrate-producing microflora of the human gut". Thesis, Robert Gordon University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310425.
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Ramsay, Alan Gregor. "Studies on the molecular biology and ecology of butyrate-producing human colonic bacteria". Thesis, University of Aberdeen, 2003. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU168350.
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The role of butyrate in the metabolism and development of a healthy colonic epithelium and thus in the prevention of colonic diseases is well documented, but the ecology of butyrate-producing bacteria is little understood. Dietary polysaccharides that are not digested in the small intestine are a major source of energy for the commensal bacteria resident in the large intestine. Resistant starch makes up a large proportion of dietary substrate reaching the human colon and is also reported to be butyrogenic. Recent studies have shown that low G+C% Gram-positive bacteria, which include butyrate-producing isolates, are among the most abundant components of the adult colonic microbiota. Here, in vitro growth experiments demonstrated that certain new butyrate producing isolates (Roseburia spp./Butyrivibrio fibrisolvens) were able to utilise starch as a sole energy source, with a growth preference for high amylopectin starches. Active starch-degrading enzyme were cell-associated in these strains and were visualised using zymogram analysis and found to be of high molecular weight. An amylase gene from Butyrivibrio fibrisolvens 16.4 was sequenced following polymerase chain reaction (PCR) amplification with degenerate oligonucleotides and chromosome walking. The putative amylase consists of an open reading frame of 4002 bp encoding a protein of 1333 amino acids with a calculated Mr of 144,470. Analysis of the multidomain organisation of this enzyme indicated that it is bound to the cell wall, with its putative catalytic domain and repeated starch-binding modules protruding into the extracellular matrix. This work also describes the use of an in vitro continuous culture fermentor system and human microbiota-associated mice (in vivo) to assess the potential of certain butyrate-producing anaerobes for probiotic and/or prebiotic applications.
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Zöllner, Robert [Verfasser], Berenike [Gutachter] Maier i Tobias [Gutachter] Bollenbach. "Linking intercellular forces to colony dynamics and fitness in bacterial populations / Robert Zöllner ; Gutachter: Berenike Maier, Tobias Bollenbach". Köln : Universitäts- und Stadtbibliothek Köln, 2019. http://d-nb.info/1182533299/34.
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Sobko, Tanja. "Influence of the microflora on gastrointestinal nitric oxide generation : studies in newborn infants and germ-free animals /". Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-779-0/.
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CHEGDANI, FATIMA. "Effects of Streptococcus Thermophilus Bacteria on rat gene expression profiles". Doctoral thesis, Università Cattolica del Sacro Cuore, 2011. http://hdl.handle.net/10280/962.
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In questo studio abbiamo analizzato l'impatto dellethermophiluds Streptococcus sull'epitelio del colon di ratto. Dopo la generazione del modello di ratto axenico e inoculato con S. thermophilus abbiamo investigato l'interazione tra il batterio e epithelo del colon di ratto. Dopo questo studio integrativo abbiamo analizzato l’espressione genica del colon usando due diversi approcci:
Ibridazione sottrattiva
I trascritti ottenuti dopo il sequenziamento dei cloni ottenuti con la SSH sono stati raggruppati in diversi categorie funzionali: arresto del ciclo cellulare e induzione del differenziamento, comunicazione cellulare e binding . due geni candidati sono stati privilegiati, krupel like fattore 4 e 14-3-3σ. Questi geni candidati sono stati analizzati mediante RT-PCR, qRT-PCR e Western Blot in animali mono-associati e in animali germ-free. I test hanno confermato che l’espressione dei geni candidati aumenta in presenza di S. thermophilus.
Microarray Analysis.
L’spressione genica è stata misurata per due gruppi di animali: i) ratti privi di germi, ii) ratti mono-associati con il ceppo LMD9 di Streptococcus thermophilus. I risultati delle analisi dei dati di microarray indicano che Streptococcus thermophilus influenza notevolmente l'espressione genica nelle cellule epiteliali del colon.In this study we have investigated the impact of Streptococcus thermophiluds on the rat colonic epithelium. After generation of the model axenic rat and inoculated with S. thermophilus we have investigated the interplay between bacteria and host colon. Colonic epithelium gene expression was investigated also, with two different approaches: Suppressive Subtractive Hybridization. The subtraction library was prepared subtracting mRNA between epithelial cells from colonic mono-associated rats and germ-free rats. The transcripts generated by SSH were grouped into divers Functional groups: cell-cycle arrest and induction of differentiation; cell-communication and binding. Tow candidates genes were privileged, krupel like factor 4 and 14-3-3σ. These candidate genes were tested by RT-PCR, qRT-PCR and Western blot in mono-associated animals and in germ-free animals. The tests confirmed that candidate genes increase their expression in the presence of S. thermophilus. Microarray analysis. Gene expression was measured in tow groups of animals: i) germ-free rats; ii) mono-associated rats inoculated with LMD9 strain of Streptococcus thermophilus. The results of microarray analysis data show that Streptococcus thermophilus remarkably affected gene expression in the colonic epithelial cells. Streptococcus thermophilus enhanced the expression of genes involved in different pathways in the host, compared to the gem free group.
34
CHEGDANI, FATIMA. "Effects of Streptococcus Thermophilus Bacteria on rat gene expression profiles". Doctoral thesis, Università Cattolica del Sacro Cuore, 2011. http://hdl.handle.net/10280/962.
Pełny tekst źródłaStreszczenie:
In questo studio abbiamo analizzato l'impatto dellethermophiluds Streptococcus sull'epitelio del colon di ratto. Dopo la generazione del modello di ratto axenico e inoculato con S. thermophilus abbiamo investigato l'interazione tra il batterio e epithelo del colon di ratto. Dopo questo studio integrativo abbiamo analizzato l’espressione genica del colon usando due diversi approcci:
Ibridazione sottrattiva
I trascritti ottenuti dopo il sequenziamento dei cloni ottenuti con la SSH sono stati raggruppati in diversi categorie funzionali: arresto del ciclo cellulare e induzione del differenziamento, comunicazione cellulare e binding . due geni candidati sono stati privilegiati, krupel like fattore 4 e 14-3-3σ. Questi geni candidati sono stati analizzati mediante RT-PCR, qRT-PCR e Western Blot in animali mono-associati e in animali germ-free. I test hanno confermato che l’espressione dei geni candidati aumenta in presenza di S. thermophilus.
Microarray Analysis.
L’spressione genica è stata misurata per due gruppi di animali: i) ratti privi di germi, ii) ratti mono-associati con il ceppo LMD9 di Streptococcus thermophilus. I risultati delle analisi dei dati di microarray indicano che Streptococcus thermophilus influenza notevolmente l'espressione genica nelle cellule epiteliali del colon.In this study we have investigated the impact of Streptococcus thermophiluds on the rat colonic epithelium. After generation of the model axenic rat and inoculated with S. thermophilus we have investigated the interplay between bacteria and host colon. Colonic epithelium gene expression was investigated also, with two different approaches: Suppressive Subtractive Hybridization. The subtraction library was prepared subtracting mRNA between epithelial cells from colonic mono-associated rats and germ-free rats. The transcripts generated by SSH were grouped into divers Functional groups: cell-cycle arrest and induction of differentiation; cell-communication and binding. Tow candidates genes were privileged, krupel like factor 4 and 14-3-3σ. These candidate genes were tested by RT-PCR, qRT-PCR and Western blot in mono-associated animals and in germ-free animals. The tests confirmed that candidate genes increase their expression in the presence of S. thermophilus. Microarray analysis. Gene expression was measured in tow groups of animals: i) germ-free rats; ii) mono-associated rats inoculated with LMD9 strain of Streptococcus thermophilus. The results of microarray analysis data show that Streptococcus thermophilus remarkably affected gene expression in the colonic epithelial cells. Streptococcus thermophilus enhanced the expression of genes involved in different pathways in the host, compared to the gem free group.
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Avezón, Campos Silvana Loreto. "Perfil bacteriológico en una colonia de cobayos de bioterio". Tesis, Universidad de Chile, 2009. http://repositorio.uchile.cl/handle/2250/131560.
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Memoria para optar al Título Profesional de Médico VeterinarioEl objetivo de los bioterios de producir y disponer de animales y sus productos para apoyar servicios y trabajos de investigación, requiere producir animales estandarizados, específicos para cada investigación, garantizando a su vez su genética y estado sanitario. Se estudió la colonia de cobayos del Bioterio del Centro de Producción de Animales de Laboratorio (CPAL) del Instituto de Salud Pública de Chile, Ministerio de Salud, con el fin de conocer su condición sanitaria. De un total de 1566 animales dispuestos en tres corralillos, se muestreó un total de 43 cobayos al azar, proporcionalmente según sexo y categorías. Estos correspondieron a dos machos reproductores, 35 hembras reproductoras, dos crías machos, una cría hembra y tres lactantes. A cada animal seleccionado se le realizó un examen clínico (constantes fisiológicas de temperatura corporal, frecuencia cardíaca, perfusión periférica, condición corporal). La eutanasia se realizó con T61 intracardíaco. Luego de la necropsia se obtuvieron, muestras de torunda nasofaríngea, raspado traqueal, pulmón, hígado, bazo y contenido cecal. Se agregaron hallazgos de tejidos o secreciones alterados. Considerando los patógenos bacterianos más frecuentes e importantes en cobayos de bioterio, se realizaron cultivos específicos para aislamientos de Bacillus piliformis, Bordetella brochiseptica, Klebsiella pneumoniae, Salmonella spp., Streptococcus pneumoniae y Yersinia pseudotuberculosis. Para Bacillus piliformis, además, las muestras se inocularon en huevos embrionados. Todos los estudios de aislamientos fueron negativos para cada una de las bacterias consideradas. Como hallazgos en el grupo de hembras reproductoras, dos presentaron abscesos subcutáneos con aislamientos de Bacillus spp., no correspondiendo a Bacillus piliformis. Seis hembras del mismo grupo presentaron abscesos mesentéricos con aislamientos de Streptococcus spp., no correspondiendo a Streptococcus pneumoniae. Ocho presentaron lesiones hepáticas atribuibles a recorridos larvales de parásitos gastrointestinales. 2 Se hallaron, además, en una cría y un lactante lesiones hepáticas atribuibles a parásitos gastrointestinales. Complementariamente, las muestras de deposiciones fueron negativas a la presencia de huevos de parásitos gastrointestinales por el método de flotación que detecta altas cargas parasitarias. Considerando que la colonia de cobayos estudiada es del tipo convencional, su calidad sanitaria es buena.
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Celiberto, Larissa Sbaglia. "Intestinal homeostasis and host defense as promoted by commensal bacteria and the colonic mucus layer /". Araraquara, 2018. http://hdl.handle.net/11449/180350.
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Orientador: Daniela Cardoso Umbelini CavalliniOrientador no exterior: Bruce A. Vallance
Coorientador: Caetano Martha Antunes
Banca: Bruce Vallance
Banca: Carla Fontana
Banca: Xiaonan Lu
Banca: Ligia Sassaki
Resumo: O trato gastrointestinal abriga a maior população de microrganismos no corpo humano, onde eles desempenham um papel importante na promoção da saúde do hospedeiro. A alteração na composição da microbiota pode levar à disbiose intestinal, que consequentemente desencadeia ou agrava doenças intestinais e extra-intestinais. Microrganismos benéficos também conhecidos como probióticos são constantemente investigados como uma terapia complementar nas doenças relacionadas à disbiose. No entanto, sua eficácia no tratamento de condições severas, como por exemplos as doenças inflamatórias intestinais (DII), é bastante variável e apresenta resultados controversos. Para abordar a importância de uma abordagem probiótica personalizada para tratar a inflamação intestinal, primeiro examinamos o efeito de bactérias personalizadas usando um modelo de colite induzida por produtos químicos. Os animais que receberam comensais isolados de suas próprias fezes foram mais protegidos contra a inflamação, pois mostraram sinais reduzidos de colite, menor dano histológico e menores níveis de marcadores inflamatórios, quando comparados aos ratos que receberam uma cepa probiótica comercial. Em seguida, o papel da mucina intestinal Muc2 e da enzima Core-1 que glicosilam foram explorados usando o modelo de colite infecciosa Citrobacter rodentium. A camada de muco intestinal é a primeira linha de defesa no intestino e é composta em grande parte pela mucina Muc2. Uma vez que quase todas as bactérias entéricas de... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The intestinal tract harbours the largest population of microbes in the human body where they play an important role in promoting the health of their host. If the composition of these microbes is altered, this may lead to dysbiosis that triggers or exacerbates intestinal and extra-intestinal diseases. Probiotics have been investigated as a complementary therapy in dysbiosis-related diseases. However, their effectiveness in treating severe conditions such as Inflammatory Bowel Disease (IBD) is quite variable and have shown controversial results. To address the importance of a personalized probiotic approach to treat intestinal inflammation, we first examined the effect of personalized bacteria using a model of chemical induced colitis. The animals that received commensals isolated from their own feces were more protected against inflammation as they showed reduced signs of colitis, less histological damage and lower levels of inflammatory markers as compared to mice given a commercial probiotic strain. Next, the role of the intestinal mucin Muc2 and the Core-1 enzyme that glycosylates it were explored using the Citrobacter rodentium model of infectious colitis. The intestinal mucus layer is the first line of defense in the intestine and is largely composed of the secreted mucin Muc2. Since almost all enteric bacteria must cross the overlying mucus layer to infect the host, the mucus-enteric bacterial interactions provide fundamental knowledge about infectious diseases as well as inflammatory conditions linked to dysbiosis... (Complete abstract click electronic access below)
Doutor
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Bosc-Bierne, Sylvie. "Bilan bactériologique des spondylodiscites infectieuses diagnostiquées par ponction-biopsie ostéo-articulaire transcutanée à l'Hôpital Lariboisiére de 1984 à 1986". Paris 5, 1990. http://www.theses.fr/1990PA05P019.
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Trinschek, Sarah Christine. "Modélisation de films minces de fluides complexes et de colonies bactériennes". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY012/document.
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Les bactéries se répandent aux interfaces en formant des colonies, qui peuvent être considérées comme des suspensions denses actives. L'objet de cette thèse est le développement et l'analyse de modèles simples pour élucider le rôle des phénomènes physico-chimiques et passifs - tels que l'osmose, la tension de surface et le mouillage - dans l'expansion des colonies bactériennes aux interfaces solide/air. Les modèles sont basés sur une description hydrodynamique des couches minces de suspensions liquides, qui est complété par des processus bioactifs.Dans un premier temps, nous nous sommes intéressés à l'expansion osmotique des biofilms. Dans ce mécanisme, la bactérie sécrète une matrice polymérique qui agit comme un osmolyte et entraîne un afflux d'eau, riche en nutriments, du substrat humide vers le biofilm. Nous avons constaté que la mouillabilité du substrat est une des déterminantes principales de la vitesse d'expansion du biofilm. En-dessous d'une mouillabilité critique l'expansion s'interrompt, bien que la colonie soit biologiquement active. Cependant, une légère réduction de la tension de surface et une amélioration de la mouillabilité qui en résulte suffisent à induire un étalement continu. Les bactéries peuvent activement contrôler la tension de surface par la production de bio-surfactants.Dans un deuxième temps, nous avons étudié l'expansion de colonies bactériennes aidée par des molécules biologiques tensioactives auto-produites. Dans ce mécanisme, des flux de Marangoni résultant d'une concentration non uniforme de molécules tensioactives aux bords de la colonie peuvent favoriser l'expansion coopérative et provoquer une instabilité de la forme axi-symétrique des colonies bactériennes. Notre modèle nous a permis de reproduire quatre modes de développement différentes, à savoir l'étalement arrêté et continu des colonies circulaires, l'étalement des colonies avec des bords légèrement modulées et la formation de doigts prononcés.Dans la dernière partie, nous avons fait un premier pas vers l'incorporation de la motilité actif des bactéries dans notre modèle et présentons donc un modèle phénoménologique pour un film mince activeBacteria colonise interfaces by the formation of dense aggregates. In this thesis, we develop and analyse simple models to clarify the role of passive physico-chemical forces and processes - such as osmosis, surface tension effects and wettability - in the spreading of bacterial colonies at solid-air interfaces. The models are based on a hydrodynamic description for thin films of liquid suspensions that is supplemented by bioactive processes.We first focus on the osmotic spreading mechanism of bacterial colonies that relies on the generation of osmotic pressure gradients. The bacteria secrete a polymeric matrix which acts as an osmolyte and triggers the influx of nutrient-rich water from the moist substrate into the colony. We find that wettability crucially affects the spreading dynamics. At low wettability, the lateral expansion of the colony is arrested, albeit the colony is biologically active. However, a small reduction of the surface tension and the resulting improvement of the wettability suffices to induce continuous spreading. This can, e.g., result from the production of bio-surfactants by the bacteria.Next, we study passive liquid films covered by insoluble surfactants before developing a model for the surfactant-driven spreading of bacterial colonies. In this spreading mechanism, Marangoni fluxes arising due to a non-uniform surfactant concentration at the edges of the colony drive cooperative spreading and may cause an instability of the circular colony shape. We find that variations in wettability and surfactant production suffice to reproduce four different types of colony growth, namely, arrested and continuous spreading of circular colonies, slightly modulated front lines and the formation of pronounced fingers.In the final part, we take a first step towards the incorporation of active collective bacterial motion in the employed thin-film framework and present a phenomenologically derived model for active polar films
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Mansoorian, Bahareh. "Effect of food matrix interaction between dietary fibre and polyphenols on their metabolism by colonic bacteria". Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/6136/.
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Background: The consumption of plant based foods has demonstrated an inverse association with disease prevalence. Among the components of plant based foods, polyphenol and fibre are two of the main contenders for many health benefits. The majority of polyphenols and fibre pass through the small intestine unabsorbed, reaching the colon where they are subjected to the action of the colonic microbiota; resulting in the production of the potentially bioactive metabolites: phenolic acids and SCFA. These metabolites are potentially responsible for many of the health benefits exerted by polyphenols rich foods and fibre. Given the recent advances in understanding the role of colonic microbiota in metabolic and immune responses, factors, which may positively or negatively modify the composition of the colonic bacteria have also received much attention. Foods rich in dietary fibre and polyphenols have the potential to modify colonic bacteria through prebiotic and antibiotic action. The potential bacterial inhibition by polyphenolics and the stimulation of bacterial growth by fibre and polyphenols means potential for both sets of compounds to influence metabolite production from each other. Polyphenols and fibre are most often present in the same foods and may be found together in plant cell walls. Thus they most often enter the colon together. We aimed to explore how the presence of these two components in the diet may impact on the metabolite production from the other by the colonic microbiota. Methods: The food matrix interaction of fibres and polyphenols was assessed using the fibres: raftiline, pectin and ispaghula, having different physio-chemical properties (rate of fermentation and viscosity) and the polyphenols: rutin and catechin, epicatechin and other polyphenols present in cocoa in vitro models of phenolic acid and short chain fatty acid (SCFA) production. The impact of ispaghula on urinary phenolic acids after cocoa ingestion was then investigated in an acute human study. In Chapter-3 the impact of the fermentable fibres on phenolic acid production from isolated parent compound: rutin in-vitro using 24 hour batch cultures using human faecal samples from volunteers (n=10) after being on a 3-day low polyphenol diet was investigated. Using the same model the impact of rutin, quercetin and their metabolites on SCFA production from raftiline, ispaghula and pectin was then investigate. The SCFA were measured by GC-FID and phenolic acids by GCMS. pH and gas were also measured. Using the same methodology the matrix interaction between raftiline, ispaghula and pectin separately on phenolic acid production from their parent compounds within their food matrix was investigated using cocoa as a rich source of polyphenols, as well as the impact of cocoa polyphenols and their metabolites on SCFA production from the fermentable fibres (Chapter-4) In Chapter-5, 24-hour urinary polyphenolic acids were measured in 5 batches (0, 0-2, 2-5, 5-8, 8-24 hour) in 12 human volunteers after ingestion of 1g paracetamol with 20g cocoa (extra brute Cocoa-Cacao Barry, Barry Callebaut, Hardricourt, France) with water, 15g of ispaghula with water or the combination of the two. Urine samples were also used for total phenol and antioxidant capacity measurement. Plasma was collected over six hours (every half hour for 4 hours and at 6th hour) and used for the measurement of total phenols as well as paracetamol concentrations for the estimation of gastric emptying rate. Breath hydrogen was used for estimation of small bowel transit time and visual analogue scales (VAS) were used for the estimation of subjective appetite response to meals. Results: The faecal fermentation of rutin resulted in the production of the following phenolic acids: PAA, 4-HBA, 3-HPAA, 4-HPAA, 3,4-DHPAA, 3-HPPA and 4-HPPA. All of these phenolic acids were significantly reduced by at least one of the three fibres, with the exception of 3-HPPA and 4-HPPA. The extent of inhibition of total sum of phenolic acids from raftiline and pectin was similar (p < 0.01) and ispaghula demonstrated the least inhibitory effect (p=0.03). Rutin and quercetin had no impact on the SCFA production from the fermentable fibres. The phenolic acids identified from cocoa faecal incubations consisted of: of PAA, 3-HPAA, 4-HPAA, 3,4-DHPAA, 3-HPPA, 4-HPPA, 3,4-DHPPA, 4-HBA, 3,4-DHBA, hippuric acid and vanillic acid. Unlike the rutin study where majority of phenolic acids were significantly reduced, in this study only four of eleven phenolic acids were affected (PAA, 3-HPAA, 4-HPAA, 4-HBA: also inhibited in the rutin study).The extent of phenolic acid reduction was the highest for pectin (p < 0.01), followed by raftiline (p < 0.01) and ispaghula (p=0.03). These phenolic acids or their parent compounds had no impact on SCFA production from the fermentable fibres. The consumption of cocoa resulted in the urinary excretion of the following phenolic acids: 3-HPAA, 4-HPAA, 3,4-DHPAA, Hippuric, 4-HPA, 4-HBA, 3,4-DHBA, Vanillic, 4-HVA, Mandelic and 4-HMA. All of which, with the exception of vanillic acid and 3,4-DHPAA, were reduced by ispaghula (Table-I). Ispaghula accelerated gastric emptying rate but had no impact on small bowel transit time. The analysis of total phenol (TP assay) concentration (plasma and urine) and antioxidant capacity (urine) did not demonstrate any difference between cocoa and ispaghula, which were both high. However when they were ingested together there was a signification reduction in both total phenol and antioxidant capacity (p < 0.01). Given that urinary and plasma concentration of total phenols was no different for ispaghula and cocoa we analysed the free phenolic and bound phenolics in both ispaghula and cocoa, showing that cocoa has significantly higher free phenolics than ispaghula, whereas bound phenolics were higher in ispaghula. The sum of bound and free total phenols was higher in cocoa than ispaghula (approximately 10 fold). Urinary, faecal SCFA were not measured as they are not validated to represent in-vivo production. Conclusion: there is a strong inhibition of phenolic acid production from polyphenol by the fermentable fibres and their metabolites. This inhibition is stronger in-vivo than in-vitro for ispaghula, which may reflect the longer interaction time in the colon and potential small bowel interaction. The production of SCFA from fermentable fibres was not inhibited by the polyphenols or their metabolites. These interactions need to be considered when assessing the bioavailability of phenolic acid production and their potential health benefits.
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Ridlon, Jason Michael. "ENZYMOLOGY AND MOLECULAR BIOLOGY OF BILE ACID 7alpha- AND 7beta- DEHYDROXYLATION BY THE INTESTINAL BACTERIA CLOSTRIDIUM SCINDENS AND CLOSTRIDIUM HYLEMONAE". VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/736.
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The collective microbial genomes within our gut(microbiome) represent a powerful metabolic force, leading many authors to call our GI flora an "organ within an organ", and the metagenomic sequencing of our microbiome, "the second human genome project". Bile acids, endogenously produced by the host liver, represent both a strong selective pressure for potential colonizers, aswell as substrates for microbial metabolism. Indeed, microbes have evolved enzymes to deconjugate bile salts, epimerize bile acid hydroxyl groups, and 7alpha-dehydroxylateprimary bile acids. The products of microbial 7alpha-dehydroxylation, secondary bile acids, are suggested by numerous lines of evidence to be involved in promoting colon carcinogenesis. 7alpha-dehydroxylating activity is a multi-step pathway, genes of which have only been identified in a small number of organisms within the genusClostridium. The biochemistry of this pathway has been largely worked out. The third step in the pathway is introduction of a delta-4-double bond; however, the gene product(s) responsible have not been identified. The baiCD and baiH genes were cloned, expressed and shown to have NAD-dependent 3-oxo-delta-4-steroid oxidoreductase activity showing stereospecificity for 7alpha-hydroxy and 7beta-hydroxy bile acid, respectively.In addition, bai genes were isolated from C.hylemonae TN271 by bidirectional genome-walking by PCR. This represents the first report of bai genes from a "low activity" 7alpha-dehydroxylating bacterium. The gene organization and sequence of the baiBCDEFGHI operon was highly conserved between C. hylemonae TN271 and the "high activity" 7alpha-dehydroxylating bacterium C. scindens VPI12708. The baiA gene was located by PCR using degenerate oligonucleotides. Bi-directional genome-walking revealed what appears to be several novel genes involved in bile acid metabolism which were also located in C. scindens VPI 12708. Expression of a 62 kDa flavoprotein and reactionwith [24-14C] 3-oxo-DCA and NADP resulted in a product of greater hydrophilicity than deoxycholic acid. The identity of this product was not determined. A second gene appears to share a common evolutionary origin with the baiF gene. A hypothesis is offered regarding the function of these homologues as Type III CoA transferasesrecognizing 5alpha-bile acids, or 5beta-bile acids (allo-bile acids). A third gene encodes a putative short chain reductase, similar in size and predicted function to the baiA gene, which may be involved in the final reductive step in the pathway. These novel genes also contained a conserved upstream regulatory region with the baioxidative genes. Finally, two genes were identified which may serve as potential drug targets to inhibit bile acid 7alpha-dehydroxylation. The first is an ABC transporter which may be co-transcribed with the other novel bile acid metabolizing genes, and what appears to be a bile acid sensor/regulator similar to the Tryptophan-rich sensory protein (TspO)/mitochondrial peripheral benzodiazepinereceptor (MBR) family of proteins.
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Sloan, David Alexander. "Colon neoplasia in an experimental model : the effects Diet, injury, and antibiotic manipulation of the gut bacterial flora". Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65941.
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Bergstrom, Kirk S. B. "The role of colonic goblet cells in host defense against attaching and effacing bacterial pathogens". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/30512.
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The non-invasive attaching and effacing (A/E) pathogens Enteropathogenic and Enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively) are a prominent subgroup of diarrheagenic E. coli, and remain an important cause of morbidity and mortality worldwide. A/E pathogens intimately attach to the surface of intestinal epithelial cells, and efface or destroy their microvilli. The intestinal epithelium is the first line of defense against A/E and all pathogens, and evidence is implicating epithelial secretory cells as playing a key role in this regard. Goblet cells are specialized secretory epithelial cells that are the sole producers of the mucus barrier lining the intestinal tract through the release of the polymeric Muc2 mucin. Goblet cells also secrete the small peptide Resistin-like Molecule-{beta} (RELMβ), which plays a direct role in host defense against parasitic helminths. Despite the abundance of which these molecules are released, little is known of their role in host-protection against A/E pathogens. I hypothesized that goblet cells play a critical role in host defense against A/E bacteria by secretion of Muc2/mucus and RELMβ into the intestinal tract. Using Citrobacter rodentium, a murine A/E pathogen that is an established model of EPEC and EHEC, my results demonstrate that goblet cells are a critical component of innate host-defense against an A/E pathogen. Studies with Muc2⁻/⁻ mice show that Muc2/mucus production was critical for limiting luminal burdens, and for flushing away pathogenic bacteria as well as commensal bacteria from the mucosa. Moreover, RELMβ was highly induced and secreted into the lumen during the first week of infection. Studies with Retnlb⁻/⁻ mice demonstrated that RELMβ production limited cecal burdens, deep penetration of colonic crypts, and severe inflammatory damage following infection. Lastly, adaptive immunity plays a role in modulating goblet cell function, by promoting a down-regulation of goblet cell-specific gene expression and protein production, including Muc2. This effect appears to reflect a generalized adaptive immunity-mediated epithelial proliferative response and is associated with clearance of surface-associated pathogens. Thus, goblet cells are critical for managing infection by an A/E bacterial pathogen. These studies highlight a novel and previously unappreciated function of goblet cells in host defense against enteric bacterial infection.
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Bentley-Hewitt, Kerry. "Impact of different dietary long-chain polyunsaturatd fatty acids on survival of probiotic bacteria in colonic cell lines". Thesis, University of East Anglia, 2010. https://ueaeprints.uea.ac.uk/24518/.
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Agvald-Öhman, Christina. "Colonization, infection and dissemination in intensive care patients /". Stockholm : Karolinska institutet, 2007. http://diss.kib.ki.se/2007/978-91-7357-075-6/.
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Kasendra, Magdalena Julia <1985>. "Clostridium difficile toxins facilitate bacterial colonization by modulating the fence and gate function of colonic epithelium". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6364/1/Kasendra_Magdalena_tesi.pdf.
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The contribution of Clostridium difficile toxin A and B (TcdA and TcdB) to cellular intoxication has been extensively studied, but their impact on bacterial colonization remains unclear. By setting-up two- and three-dimensional in vitro models of polarized gut epithelium, we investigated how C. difficile infection is affected by host cell polarity and whether TcdA and TcdB contribute to such events. Indeed, we observed that C. difficile adhesion and penetration of the epithelial barrier is substantially enhanced in poorly polarized or EGTA-treated cells, indicating that bacteria bind preferentially to the basolateral cell surface. In this context, we demonstrated that sub-lethal concentrations of C. difficile TcdA are able to alter cell polarity by causing redistribution of plasma membrane components between distinct surface domains. Taken together, the data suggest that toxin-mediated modulation of host cell organization may account for the capacity of this opportunistic pathogen to gain access to basolateral receptors leading to a successful colonization of the colonic mucosa.
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Kasendra, Magdalena Julia <1985>. "Clostridium difficile toxins facilitate bacterial colonization by modulating the fence and gate function of colonic epithelium". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6364/.
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The contribution of Clostridium difficile toxin A and B (TcdA and TcdB) to cellular intoxication has been extensively studied, but their impact on bacterial colonization remains unclear. By setting-up two- and three-dimensional in vitro models of polarized gut epithelium, we investigated how C. difficile infection is affected by host cell polarity and whether TcdA and TcdB contribute to such events. Indeed, we observed that C. difficile adhesion and penetration of the epithelial barrier is substantially enhanced in poorly polarized or EGTA-treated cells, indicating that bacteria bind preferentially to the basolateral cell surface. In this context, we demonstrated that sub-lethal concentrations of C. difficile TcdA are able to alter cell polarity by causing redistribution of plasma membrane components between distinct surface domains. Taken together, the data suggest that toxin-mediated modulation of host cell organization may account for the capacity of this opportunistic pathogen to gain access to basolateral receptors leading to a successful colonization of the colonic mucosa.
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Jung, Deborah Osterholm. "QUANTITATIVE ANALYSIS OF THE TOTAL BACTERIA, LACTOBACILLUS, AND BIFIDOBACTERIUM COLONIC MICROFLORA IN RATS FED CONVENTIONAL, PREBIOTIC, AND PROBIOTIC SOY DIETS". OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1778.
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Research suggests that specific compositions of gut microbiota can directly affect energy harvesting and fat storage, which may indicate a potential role of intestinal bacteria in the regulation of body weight (i.e., obesity). The purpose of the current study was to determine if prebiotic- and probiotic-based diets modify gut microbiota in genetically obese rodents. For this, female Zucker diabetic fatty (ZDF) rats were assigned diets containing fructooligosaccharides (FOS), Bifidobacterium (BIF), or Lactobacillus (LAC) for three weeks. qPCR was then used to measure levels of colonic Bifidobacterium, Lactobacillus, and total bacteria. At termination, there was no significant difference in Lactobacillus levels between diets. However, there was significantly less Bifidobacterium in BIF vs. FOS or LAC-fed rats. The evidence in this study shows there were no significant differences in Lactobacillus levels between any of the feeding groups and the control group, supporting the conclusion that ingestion of any of the tested supplemented feed does not statistically modulate Lactobacillus numbers in female ZDF rats. However, the rats from the Bifidobacterium and FOS feeding groups had significantly higher colonic Bifidobacterium levels than the control group from ingesting the supplemented feed, indicating that the presence of the probiotic Bifidobacterium animalis subspecies lactis and the prebiotic FOS stimulated the growth of Bifidobacterium.
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Adámek, Jakub. "Zpracování obrazu Petriho misek". Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2015. http://www.nusl.cz/ntk/nusl-264981.
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This master thesis deals with image processing of Petri dishes. The first part is about terms and procedures in laboratory practice. The following part is about devices and algorithms for image analysis of Petri dishes. The second part is about draft and implementation of own colony counting application, which was developed in cooperation with the microbiological laboratory. The application is developed for mobile devices running Android OS. The master thesis also includes the design and creation of two lighting units, which uses as an accessory for better results in the analysis of Petri dishes. In conclusion are presented results, compared lighting units and various types of mobile devices, on which the application was tested.
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Rigsbee, Laura J. "Interrogation of the Distal Gut Microbiota of Healthy Adolescents and those with Irritable Bowel Syndrome". Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1314040541.
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ELLMERICH, STEPHAN. "Streptococcus bovis et cancer colorectal : etude des mecanismes moleculaires impliques dans les interactions bacteries-cellules et consequences fonctionnelles de ces interactions (doctorat : pharmacologie)". Strasbourg 1, 1998. http://www.theses.fr/1998STR15100.
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