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Chou, Lan-Szu. "Isolation and Biochemical Characterization of Acid- and Bile- Tolerant Strains of Lactobacillus Acidophilus and Bifidobacterium Bifidum." DigitalCommons@USU, 1997. https://digitalcommons.usu.edu/etd/5427.
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Lactic acid bacteria have been reported to be used as a health adjunct in food for u many years. However, these health benefits have not been proven. and how these bacteria pass through the digestion process and remain viable in the human intestinal tract is still not clear. The aim of this work was to isolate mutants from Lactobacillus acidophilus or Bifidobacterium bifidum that could tolerate the conditions of the digestion process (low pH and bile conduction) and to characterize these isolated mutants.
Acid- and bile-tolerant mutants of L. acidophilus were isolated from parental strains successfully using natural selection techniques. These mutants survived and grew at conditions of pH 3.5 with 0.2% mixed bile salts added. After the selection, phenotypic characterization was identified to further clarify desirable traits for use as probiotic adjuncts in foods. These phenotypic characteristics included protease, aminopeptidase, ß-galactosidase, and bile salt hydrolase activity. Based on different protease, aminopeptidase, and ß-galactosidase activity, selected acid- and bile-tolerant mutants contained different growth characteristics compared with their parents. All the isolates tested showed different bile salt hydrolase activity, and this activity was not strain and medium dependent.
Plasmid profiles and fatty acid analysis were conducted to provide more information of these acid/bile tolerant isolates and whether or not they were mutants from their parent strains rather than only adapted variants. Results showed the acid-/bile-tolerant isolates contained different plasmid profiles and cell wall fatty acids compared with their parents, which indicated these isolates were mutants. Protein expression by two-dimensional gel electrophoresis showed different protein expression patterns between acid- and bile-tolerant mutants and their parents. fm1her suggesting these isolates were mutants. We observed the protein production in parent strains decreased as the pH decreased. and protein expression in mutants remained the same as pH decreased.
Two of the proposed health benefits of probiotic bacteria are anticholesterol activity and antimicrobial activity. These were evaluated using selected acid- and bile-tolerant mutants. Results showed no decrease of cholesterol in the test medium during bacterial growth. The observed antimicrobial activity was due to the presence of active cells. and this may relate to the acid production during cell growth and not to the production of antimicrobial substances.
We concluded that the acid-/bile-tolerant isolates were mutants, and they survived and grew better in harsh environments compared with their parent strains. These mutants may be useful as a food adjunct in the future, but further study is needed to establish their use and possible probiotic benefits.
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Grossová, Marie. "Tvorba biofilmu u probiotických bakterií a jejich zpracování do pevné lékové formy." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2016. http://www.nusl.cz/ntk/nusl-263349.
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The aim of present work is cultivation of probiotic bacteria L. acidophilus, B. breve and B. longum in such a way that the culture forms cells clusters or comprehensive biofilm on the variety of free carriers. Biofilm formation of L. acidophilus on the silica from point of view bile and acid tolerance in gastrointestinal tract was studied. While the number of living cells in planktonic form (planktonic form) at pH 1 fell by 30 %, the viability of the biofilm cells was maintained to 90 % under the same environmental conditions. The biofilm culture showed also the protection against environment contained bile. Furthermore, the possibilities of drying procedures of biofilm cultures used as commercial technologies in pharmaceutical industry were studied. The comparison of freeze-drying and fluidization bed drying showed, that freeze-drying is more suitable method, which is able to achieve higher amount of viable cells after drying than fluidization bed drying. The effectivity of freeze-drying method is dependent on the selection of suitable cryprotective medium. In this case, about 90 % higher viability after freeze drying was achieved in comparison with fluidization bed drying. Finally, the industrial processing of probiotic strains into the solid dosage form was studied. Tablets should be produced at hardness between 70 and 90 N and water activity of tablet mixture can be maintained below 0.3. Consequently, the drying step of the tablets in a hermetically closed space with at least 10 % of silica gel must be ensured. Thereafter, the tablets contain (5.4 ± 0.7)109 viable cells after 6 months of drying process. Capsule production technology has no significant effect on the cell‘s viability during production. The triplex blistering foil for primary blistering of probiotic capsules was chosen. The triplex foil, which has low values of water vapour transition rate (0.07 g H2O / (m2 × day) and oxygen transition rate (0.01 cm3/m2 × day), was chosen. Other studied blistering foils commonly used in the pharmaceutical industry are not suitable for long storage of solid dosage forms contained probiotics.
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Villeger, Romain. "Etude in vitro des propriétés probiotiques de bactéries du genre Bacillus : Interaction avec l’hôte et effets de l’association avec un prébiotique." Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0066/document.
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Les probiotiques sont des microorganismes vivants qui, lorsqu’ils sont ingérés en quantité adéquate, peuvent exercer des propriétés bénéfiques sur la santé de l’hôte. Les souches de Bacillus utilisées en tant que probiotiques ne sont pas colonisatrices du tractus intestinal, mais sont des résidents transitoires du microbiote. Ce travail fait l’investigation in vitro de l’association, qualifiée de synbiotique, entre une souche probiotique de Bacillus subtilis et une source carbonée prébiotique, composé alimentaire peu digéré par les enzymes intestinales mais utilisable par les bactéries dans l’intestin. L’étude de cette association met en évidence la capacité de la souche à utiliser les isomaltooligosaccharides (IMOS) prébiotiques comme unique substrat carboné. L’effet positif de ce substrat sur la tolérance à la bile de la souche a été démontré in vitro. Les résultats d’une analyse protéomique faisant l’étude des enzymes clés impliquées dans le métabolisme des IMOS, ainsi que d’autres biomarqueurs d’intérêt probiotique, sont en cours d’exploitation. Ce travail préliminaire d’investigation de l’association synbiotique entre les IMOS prébiotiques et la souche probiotique B. subtilis, aboutira à des essais in vivo. Les effets bénéfiques des probiotiques du genre Bacillus, notamment au niveau de la modulation du système immunitaire, résultent de l’interaction entre les molécules de la surface bactérienne et les cellules de l’intestin. Les mécanismes moléculaires à l’origine de l’immunomodulation sont mal connus, alors que leur compréhension est nécessaire à l’optimisation de l’utilisation du probiotique. Un deuxième volet de ce travail concerne la comparaison des structures d’entités moléculaires de surface de trois Bacilli probiotiques, les acides lipotéichoïques (LTAs), et leurs activités immunologiques respectives. Une étude structurale des LTAs par des méthodes biochimiques et par RMN a permis de mettre en évidence la diversité structurale au sein du même genre Bacillus. Le rôle clé de la D-alanine dans l’activité biologique de ces antigènes bactériens a été démontréProbiotics are live microorganisms, which when administered in adequate amounts confer a health benefit on the host. Bacillus probiotic strains are not able to colonize the gut, and are considered as transient residents of the microbiota. Prebiotic are non-digestible food ingredients that could stimulate growth of bacteria in the gut. This work investigates the in vitro effect of a prebiotic isomaltooligosaccharide (IMOS) on the growth of a probiotic strain Bacillus subtilis. This study highlights the ability of the strain to use IMOS as unique carbon source. A comparative proteomic analysis investigates the main enzymes implicated in the prebiotic metabolism, and biomarkers possibly involved in probiotic effects. This preliminary work, which studies the synbiotic association between a probiotic and a prebiotic, will lead to in vivo assays. Beneficial effects of probiotic Bacilli, mainly modulation of intestinal immune system, result from interaction between bacterial cell-wall molecules and intestinal cells. The molecular origin of immunomodulatory mechanisms are poorly understood, while understanding is needed to optimize the use of probiotics. A second part of this work consists in comparing the structure of a molecular cell-wall component named lipoteichoic acids (LTA) from three Bacillus probiotic, a molecular cell-wall component of Gram positive bacteria, and their immunological activity. A structural study, using biochemical determinations and NMR spectroscopic analysis, highlights the structural diversity between LTAs from different Bacillus species. The key role of D-alanine substituents in the biological activity of these bacterial antigens has been demonstrated
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Benson, Gregory Martin. "Studies on bile acid sequestrants and bile acid metabolism in the hamster." Thesis, Royal Veterinary College (University of London), 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518089.
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Torchia, Enrique C. "The role of intracellular bile acid binding proteins in bile acid transport and cytoprotection." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ60354.pdf.
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Trusova, Tatyana. "Quantitative estimation of bile acid conjugates in human bile using HPLC /." Connect to online version, 1995. http://hdl.handle.net/1989/3555.
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Zheng, Zhi-Ying 1957. "Bile acid-induced DNA damage in bacteria." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/291421.
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Bile acids have been implicated by epidemiologic evidence as causative agents in colon cancer. Previous studies have indicated that the bile acids damage DNA. However, the conjugated forms of bile acids (eg. tauro conjugates) have not been tested for interaction with DNA. The present study compared the DNA-damaging ability of unconjugated and conjugated bile acids using the E. coli SOS test system. The E. coli tester strain was incubated with the bile acids and conjugated bile acids. Both cell survival and induction of the SOS response was measured. Among unconjugated bile acids, deoxycholate, chenodeoxycholate, and lithocholic acid were confirmed as DNA damaging agents by a decrease in surviving fraction and increase of the fraction of blue colonies undergoing SOS induction with increasing doses. Cholate, however, did not cause DNA damage by these criteria. Among the conjugated bile acids, taurochenodeoxycholate caused as much DNA damage as chenodeoxycholate. Taurodeoxycholate caused DNA damage, but had less of an effect than deoxycholate. Taurocholate and taurolithocholate failed to show a DNA damaging effect.
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D'Souza, Lawrence Joseph. "Bile Acid Based Molecular Tweezers And Crown Ethers." Thesis, Indian Institute of Science, 1995. http://hdl.handle.net/2005/114.
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Chapter 1. Introduction to Molecular Tweezers
Whitlock and Zimmerman developed a class of molecular hosts, popularly known as molecular tweezers, which sandwich aromatic guests by ii=ii interaction. Chapter 1 summarizes molecular tweezers of various kinds which have recently been synthesized.
Chapter 2. Design and synthesis of "Bile Acid-Based Molecular Tweezers" Bile acids have a rigid backbone, and the array of hydroxyl groups separated by 5-7 A provides opportunities for the attachment of binding surfaces such as two extended chromophoric units.
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Kiroff, George Kosta. "Oesophageal mucosal injury by acid and bile salt /." Title page, table of contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09MS/09msk59.pdf.
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Thesis (M.S.)--University of Adelaide, Dept. of Surgery, 1989.The experimental work described was performed in the Department of Surgery of the University of Adelaide during 1982-1983. Typescript (photocopy). Includes bibliographical references (leaves 191-211).
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Bajor, Antal. "Bile acid induced diarrhoea : pathophysiological and clinical aspects /." Göteborg : Dept. of Internal Medicine, Institute of Medicine at Sahlgrenska Academy, University of Gothenburg, 2008. http://hdl.handle.net/2077/9840.
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Pattni, Sanjeev. "Mechanisms of idiopathic bile acid malabsorption and diarrhoea." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11109.
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Bile acid malabsorption or diarrhea (BAM or BAD) is a syndrome of chronic watery diarrhoea diagnosed predominantly by a SeHCAT test and less commonly by measuring levels of 7-hydroxy-4-cholesten-3-one (C4) and furthermore responds to bile acid sequestrants (BAS). Primary bile acid diarrhoea (PBAD) is the condition with no definitive cause and is under diagnosed, often being labelled as IBS-diarrhoea with an associated burden of disease for patients. Recently an alternative mechanism for PBAD involving impaired Fibroblast Growth Factor (FGF19) production has been proposed. Aims: The primary aims were to prospectively recruit patients with chronic diarrhea, and define them into groups of BAD, or chronic diarrhoea with normal SeHCAT; characterisation with SeHCAT, C4 and serum FGF19; investigation of genetic differences involved in bile acid metabolism. Methods: 152 patients recruited had routine investigations for chronic diarrhoea including SeHCAT test. Fasting serum FGF19, C4 and bile acids levels were measured from blood samples and relationships examined; FGF19 optimisation, response of BAS on PBAD patients and on FGF19 levels, effect of bowel preparation & short bowel syndrome (SBS) on FGF19 levels were measured. 11 PBAD patients were studied through the day to examine variations in FGF19. 6 SNPs in genes involved in bile acid metabolism were analysed in PBAD patients. Results: Significantly lower fasting levels of FGF19 and increased levels of C4 were seen in patients with BAD with associations with Body Mass Index. Sensitivities and specificities for FGF19 against known tests were calculated. Excellent responses to BAS with no significant effect of bowel preparation on FGF19 and variable patterns during the day were seen. Reduced FGF19 levels were seen in SBS. SNPs studied in PBAD and control patients have yet to show any significant differences in frequencies. Conclusion: This research has confirmed that levels of an easily measurable and stable hormone, FGF19 are reduced in patients with BAD and is not affected by chronic diarrhoea per se. The work provides evidence of a disordered FGF19 production in PBAD patients, failing to reduce bile acid secretion and resulting in excess bile acids entering the colon causing BAD.
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Morgan, Sherif. "The Bile Acid, Deoxycholic Acid, Modulates IGF-IR Function in Colon Cancer Cells." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/194122.
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Deoxycholic acid (DCA) is a secondary bile acid postulated to be involved in the etiology and the progression of colorectal cancer, but its specific mechanisms are not fully understood. DCA has been shown to induce apoptosis allowing selection for apoptosis-resistant cells, which highlights the importance of understanding the mechanisms of action of DCA. Previously, it has been demonstrated that DCA perturbs the plasma membrane, leading to the activation of receptor tyrosine kinases. Because the insulin-like growth factor-1 receptor (IGF-IR), a receptor tyrosine kinase, is demonstrated to play a significant role in protecting colorectal cancer cells from apoptosis, we hypothesized that DCA modulates IGF-IR functions in colorectal cancer cells. We demonstrated that DCA induced the dynamin-dependent endocytosis of IGF-IR through both clathrin-mediated and caveolin-1-dependent mechanisms. Endocytosis of IGF-IR sensitized cells to DCA-induced apoptosis, which demonstrated that IGF-IR played a role in protecting cells against DCA-induced apoptosis. Since DCA-induced endocytosis of IGF-IR was determined to be a caveolin-1 dependent process, caveolin-1 knockdown in HCT116 (HCT116-Cav1-AS) prevented the DCA-mediated endocytosis of IGF-IR. However, we observed an increased sensitivity of DCA-induced apoptosis in the Cav1-AS cells. This suggested that caveolin-1 knockdown altered the plasma membrane dynamics such that although IGF-IR was maintained at the plasma membrane, it facilitated a pro-apoptotic signal. We demonstrated that DCA induced the activation of the pro-apoptotic p38 signaling pathway in HCT116-Cav1-AS, but not in HCT116-Mock, via IGF-IR. Inhibition of both the IGF-IR and p38 independently in HCT116-Cav1-AS significantly decreased their sensitivity to DCA-induced apoptosis. These observations demonstrated that, in a caveolin-1 dependent manner, IGF-IR played a dynamic role in the DCA-mediated apoptosis. Finally, we provided preliminary evidence demonstrating that autophagy played a central role in protecting DCA-resistant cells from DCA-induced apoptosis.Since resistance to DCA also confers apoptosis-resistance, understanding the mechanisms that lead to or prevent DCA-induced cell death is significant, since they can lead to the development of novel therapeutic strategies to sensitize apoptosis-resistant colorectal cancer cells to undergo cell death.
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Lundåsen, Thomas. "Studies on the hormonal regulation of bile acid synthesis /." Stockholm, 2007. http://diss.kib.ki.se/2007/978-91-7357-053-4/.
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Geenes, Victoria Louise. "Placental bile acid homeostasis in norma and pathological pregnancy." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508943.
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Jolly, Arthur James. "The role of acid and bile in oesophageal carcinogenesis." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436434.
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Schultz, Francisca. "Bile acid signalling in the fetal heart and myometrium." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/58279.
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Intrahepatic Cholestasis of Pregnancy (ICP) is a liver disease that affects approximately 1% pregnancies in the United Kingdom. ICP is characterised by an increase in maternal serum bile acids (BA), as well as a change in bile acid composition, whereby the increase in primary bile acids, taurocholic acid (TC) and taurochenodeoxycholic acid (TCDCA) is most pronounced. ICP is characterised by maternal symptoms and can be complicated by adverse events for the fetus, the latter of which occur more commonly in pregnancies complicated by high maternal serum bile acid levels. Adverse events that may complicate ICP pregnancies include spontaneous preterm labour, fetal distress, fetal heart arrhythmia and even intrauterine death in the third term of pregnancy. The aetiology of the fetal death is still poorly understood and is thought to occur suddenly. This thesis aims to investigate the effect of bile acids on the models of the human fetal heart and elucidate the mechanism of action of the protective role of UDCA. In addition, interaction between cardiomyocytes and fibroblasts will be investigated. Potential mechanisms of protection against bile acid induced fetal arrhythmia were investigated in different fetal heart models. The different models of the fetal heart will be described first, which include previously used models and a novel model using cells isolated from human fetal tissue. The effect of bile acids on these models will be described subsequently, with the focus on prevention of TC induced arrhythmias using Ursodeoxycholic acid (UDCA) and NorUrsodeoxycholic acid (NorUDCA). Human fetal heart tissue was obtained from terminations of pregnancy and for the first time beating cardiomyocytes were obtained. Characterisation of cardiac markers such as α-Actinin in these cells shows that there are similarities between neonatal rat, human fetal cardiomyocytes and the induced pluripotent stem cell-derived cardiomyocytes (iPS-CM) from Cellular Dynamics (CDI). Upon addition of TC to human fetal cardiomyocytes and CDI adverse effects occurred, including decreased spontaneous beating and prolongation of calcium transients and action potentials. Both UDCA and NorUDCA were not toxic to neonatal rat cardiomyocytes and fibroblasts, as used in the model and prevented TC-induced adverse effects. It was previously shown that there was a transient appearance of myofibroblasts and that these myofibroblasts play a role in TC induced arrhythmias. This thesis investigates role of fibroblasts and myofibroblasts in bile acid mediated arrhythmias. Addition of TC to human fetal and neonatal rat fibroblasts led to further depolarisation of these cells which could potentially depolarise connected cardiomyocytes. UDCA and NorUDCA on the other hand hyperpolarised these cells, which may be a potential mechanism of the protection seen in the models. UDCA and NorUDCA may act via modulation of the Sulfonylurea Receptor (SUR), a subunit of the ATP-sensitive inward rectifying potassium channel (KATP channel). This channel is involved in the regulation of the membrane potential of the cell. The interaction between cardiomyocytes and fibroblasts and the role of gap junctions in this was also investigated. Page | 4 Maternal symptoms include pruritus of the skin. Pruritus is defined as itching without a visible rash, which can become very severe in women with ICP. The pruritus usually resolves quickly after delivery of the baby. In addition, high bile acid levels are associated with increased risk of spontaneous preterm labour. The mechanism by which bile acids induce spontaneous preterm labour is not well understood and this thesis aims to further elucidate bile acid associated receptors and labour associated proteins expression levels. Expression levels of nuclear and membrane-bound bile acid receptors were investigated in myometrium tissue of labouring and non-labouring patients at term. FXR, one of the main nuclear bile acid receptors was not expressed. LXRα, LXRβ, PPARα and PPARγ were expressed as were the bile acid G-protein coupled receptor TGR5 and muscarinic receptor M5, while some muscarinic receptors (M1, M3 and M4) were not. It is difficult to obtain human myometrial tissue from earlier gestation, as the tissue is obtained from caesarean sections usually of non-labouring term pregnancies. This makes studies into the causes of preterm labour more difficult, especially those where high bile acid levels are involved, as it is often not possible to obtain consent for tissue collection from patients undergoing an emergency caesarean section due to difficulties whilst in term or preterm labour. Therefore other models could help elucidate the mechanisms behind early labour. For this reason novel protocols using a combinatory method called CombiCult (Plasticell) were developed which led to the differentiation of human embryonic (ES) and induced pluripotent stem (iPS) cells into myometrial smooth muscle cells (SMCs) in collaboration with Plasticell and these protocols will be described in this thesis. The work presented in this thesis provides new insight into the effect of bile acids on the fetal heart, with the focus on the development of novel cellular models of the human heart. The characterisation of human fetal cardiomyocytes and CDI was carried out using immunofluorescence staining of cardiac markers, which show changes upon maturation of the heart. Both the CDI and human fetal cardiomyocytes show an immature phenotype of these markers, similar to the neonatal rat cardiomyocytes. Optical recording of human fetal cardiomyocytes containing naturally occurring myofibroblasts showed that, similar to the neonatal rat model of the fetal heart, TC leads to calcium transient duration prolongation which can be prevented by UDCA. It was shown that Cx43 is involved in this interaction and that the cardiomyocytes and myofibroblasts are functionally coupled by GJs. Furthermore, work presented in this thesis provides further insight into the expression bile acid receptors in the myometrium, by providing evidence of the expression of various bile acid sensitive receptors, including the GPCR TGR5. Finally, for the first time, novel protocols were developed for the differentiation of myometrial smooth muscle cells.
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Opiyo, Monica Naomi. "The role of glucocorticoid metabolism in bile acid homeostasis." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25673.
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Alterations in glucocorticoid (GC) biosynthesis and metabolism are associated with a variety of pathophysiological disorders including cholestasis, diabetes and other metabolic disorders. Bile acids (BA) are also important modulators of metabolic functions and regulate cholesterol, triglyceride and glucose homeostasis as well as being critical for dietary fat digestion, enterohepatic function, and postprandial thermogenesis. In intact cells and in vivo, the 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) enzyme converts inactive GC precursors (cortisone in humans, and 11-dehydrocorticosterone in mice and rats) into their active forms (cortisol and corticosterone, respectively) thereby amplifying local intracellular GC levels. Interconversion by 11β-HSD1 of other sterols has also been described. These include conversions of 7keto-cholesterol to 7β-hydroxycholesterol, 7-oxodehydroepiandrosterone (7-oxo-DHEA) to 7α-hydroxy- and 7β-hydroxy DHEA, 7- oxo-lithocholic acid (LCA, a bile acid; BA) to chenodeoxycholic acid (CDCA, a 7α- hydroxylated BA) and ursodeoxycholic acid (UDCA, a 7β-hydroxylated BA) in human liver microsomes. In the liver, BA inhibit 11β-HSD1 but whether 11β-HSD1 regulates BA homeostasis is unclear. Evidence of molecular regulation of the enterohepatic recycling of bile acids by liver glucocorticoid receptor (GR) in mice does suggest a role for 11β-HSD1. It was therefore hypothesised that disruption of 11β-HSD1 expression in mice would impair BA recycling and might affect the relative concentrations of BA within the enterohepatic circuit. The primary objective of the current work was to investigate the impact of altered 11β-HSD1 on BA homeostasis. This was achieved using genetically modified mouse models with altered 11β-HSD1 expression, either globally or restricted to hepatocytes. BA are stored in the gall bladder and are released postprandially, to aid digestion. It was hypothesised that 11β-HSD1 deficiency might the affect the process of postprandial gall bladder emptying/refilling. Mice with global 11β-HSD1 knockout (Hsd11b1-/-) and age-matched control mice (C57Bl/6) were either fasted for 4h and culled or fasted for 4h and re-fed for another 4h before culling. Their response to fasting and re-feeding was assessed with specific focus on organs associated with BA recycling in the enterohepatic circuit (liver, gall bladder, serum and small intestine). Gall bladders of fasted Hsd11b1-/- and C57Bl/6 mice had similar volumes of bile but in fasted Hsd11b1-/- mice, BA concentrations were higher in serum and liver. As expected, re-feeding caused gall bladder emptying in C57Bl/6 mice with consequent increased serum and liver bile acid concentrations. In Hsd11b1-/- mice, the gall bladder did not empty and serum and liver BA concentrations were similar to the fasted state. To explore possible reasons for this, levels of mRNA encoding proteins known to be involved in hepatic BA transport were quantified using real-time q-PCR. Levels of mRNA encoding NTCP/ SCL10A1/ SCL10A1, the transporter responsible for most hepatocyte BA uptake, were increased in livers of fasted Hsd11b1-/- mice whereas levels of Slc51b mRNA, encoding the OST- transporter that facilitates BA removal from liver to the systemic circulation, and levels of Mrp2 and Atp8b1/FIC1 mRNAs (both encoding proteins which transport BA from liver into gall bladder) were decreased. This suggests that in fasted Hsd11b1-/- mice, BA transporter expression is altered to increase BA influx into hepatocytes and decrease efflux, to compensate for reduced levels of liver BA. These data together imply that bile acid recycling is controlled by 11β-HSD1 activity which regulates gall bladder emptying, hepatic BA concentration and BA transporter activity to ensure continuity of BA recycling within the enterohepatic circuit compartments. These changes may also affect digestion of lipids and fat-soluble micronutrients. Because 11β-HSD1 can directly metabolise secondary BA, it was predicted that 11β-HSD1 deficiency would lead to changes in the BA profile. Profiling of BA in the gall bladder was performed using mass spectrophotometry. In Hsd11b1-/- mice, 7α-hydroxylated BA predominated (cholic acid [CA]>α-muricholic acid [α- MCA]>CDCA>others), in contrast to C57Bl/6 mice in which 7β-hydroxylated BA predominated (ω-MCA>β-MCA>UDCA>others). The ratio of 7α:7β acids was therefore >100-fold greater in Hsd11b1-/- mice. This suggests that 11β-HSD1 either directly or indirectly controls the epimerisation of 7α- to 7β- hydroxylated BAs. Measurement of mRNAs encoding proteins important for hepatic BA biosynthesis in livers of fasted Hsd11b1-/- mice showed decreased expression of Scarb1/SR-B1, Cyp39a1 and Cyp27a1 (though with no change in levels of CDCA, the product of CYP27A1, in liver or bile fluid), compared to fasted control mice. Hepatic levels of Gpbar1/TGR5/GPBAR1 and Cyp3a11 mRNAs, encoding proteins important in BA detoxification, were increased and decreased, respectively. This suggests that Gpbar1/TGR5/GPBAR1, encoding G-protein coupled bile acid receptor (also called TGR5/GPBAR1) and an FXR target, could be induced to detoxify 7α-hydroxylated BA whereas expression of Cyp3a11, which catalyses the conversion of LCA to hyodeoxycholic acid (HDCA) is decreased; bile fluid of Hsd11b1-/- mice contained lower levels of LCA and little to no HDCA, though LCA and HDCA levels in liver were unaltered. Currently, the functional differences between 7α- and 7β- hydroxylated BA are not clear. However, these findings could have significant implications for bile acid-mediated transcription which, in turn, might affect lipid and sterol metabolism. Also, alterations in BA composition may have other physiological consequences via other pathways. Because cholesterol is the precursor of BA synthesis, it was hypothesised that western diet (WD) (containing cholesterol) would exacerbate and/or alter the phenotype of Hsd11b1-/- mice. Gall bladder weights of fasted Hsd11b1-/- and control C57Bl/6 mice did not change with western diet compared to chow diet. In control C57Bl/6 mice, the total BA concentration in the gall bladder increased in response to WD in comparison to chow diet. In contrast, Hsd11b1-/- mice showed no change in total BA concentration when fed on WD in comparison to chow. These data indicate that 11β-HSD1 is required by mice for the normal increase in total BA concentration in bile in response to dietary cholesterol. BA profiling of bile from control mice fed on WD showed no difference in the relative amounts of 7β-hydroxylated BA and 7α-hydroxylated BA to littermates fed on chow diet with the exception of β–MCA which increased, and α–MCA which decreased. Like chow-fed Hsd11b1-/- mice, BA profiling of bile from WD-fed Hsd11b1-/- mice showed a significant decrease in relative levels of 7β-hydroxylated BA (UDCA < β-MCA < others) and an increase in percentage of 7α-hydroxylated BAs (CA>α-MCA>CDCA>others) compared to C57Bl/6 controls. These data show that Hsd11b1-/- mice fail to show the normal increase in 7β-hydroxylated BA and decrease in 7α-hydroxylated BA observed in control mice in response to a cholesterol containing diet, suggesting 11β-HSD1 deficiency blunts the influence of cholesterol on BA composition. Measurement of hepatic mRNAs encoding BA transporters suggest that hepatocyte uptake of BA is decreased in C57Bl/6 on WD compared to those mice on chow diet, whereas this was not the case in Hsd11b1-/- mice where hepatic expression did not change with diet. Thus, Hsd11b1-/- mice failed to increase expression of Ntcp/ Scl10a1/ Scl10a1 appropriately, suggesting impaired hepatic BA uptake, while Slc51b (encoding OST-β) expression was increased, compared to control mice, possibly to reduce hepatic BA concentration by transporting BA out of hepatocytes into the systemic circulation. Therefore, Hsd11b1-/- mice may adapt to a cholesterol-induced increase in hepatic BA by blunting hepatic BA uptake via NTCP/ SCL10A1/ SCL10A1 and increasing hepatic efflux via OST-β. The effects of 11β-HSD1 deficiency upon BA recycling and BA profile and concentration within the enterohepatic circuit, could reflect 11β-HSD1 action within the liver or could be due to actions in other tissues.To investigate the role of hepatic 11β-HSD1 specifically, 11β-HSD1 liver-specific knockout (Hsd11b1LKO), 11β- HSD1 liver-specific over-expressors (Hsd11b1LOE) and control mice with exon 3 of the Hsd11b1 gene “floxed” (Hsd11b1F) were studied. Findings from this study indicate a role for 11β-HSD1 in adaption to dietary cholesterol and suggest that hepatic 11β-HSD1 (as opposed to 11β-HSD1 in extra-hepatic tissues) is the main factor regulating BA metabolism. Also, work from this thesis demonstrates 11β-HSD1 is an important regulator of gall bladder emptying and filling, an important component of enterohepatic bile acid recycling. Based on these findings it is anticipated that therapeutic use of 11β-HSD1 inhibitors will result in BA imbalances within the enterohepatic circuit and therefore BA homeostasis. Care must therefore be observed when implementing therapeutic use of 11β-HSD1 inhibitors, with particular focus on patients with cholestasis, Addison’s disease and critically ill patients who already have known BA imbalances in their enterohepatic system.
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Watts, Joseph. "The synthesis of A-ring fluorinated bile acid analogues." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/410301/.
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Bile acids are physiological detergent molecules with a function to absorb dietary lipids and hydrophobic molecules in the gastrointestinal tract. It has emerged that bile acids are also agonists for the FXR nuclear receptor and the TGR5 membrane-bound receptor, and are key in regulating metabolism via both genomic and non-genomic factors. It is also apparent that bile acids could play an important role in the treatment of Parkinson’s disease and some cancers. A number of pharmaceutical companies have developed selective BA receptor agonists, with some progressing through clinical trials for a variety of metabolic disorders. Fluorine is used extensively in property optimisation due to its ability to modify a plethora of physicochemical effects. By selectively introducing fluorine into the bile acid skeleton, it is possible to modify hydrogen bonding properties, and thus improvements in receptor binding are conceivable. This thesis describes the synthesis of a number of fluorinated bile acid analogues, along with a discussion of some early biological results. Two interesting cases of an intramolecular C-F•••H-O hydrogen bond within the bile acid skeleton will also be presented.
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li, qingjiang. "Chemical investigations into the physiology of bile acid skeletons." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1354810854.
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Li, Tiangang. "PREGNANE X RECEPTOR REGULATION OF BILE ACID METABOLISM AND CHOLESTEROL HOMEOSTASIS." Kent State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=kent1132160196.
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Qian, Jiang. "Studies of Sulfur Reduction of Taurine and Taurine-Conjugated Bile Acids by Bile acid 7α-Dehydroxylating Bacteria." TopSCHOLAR®, 2000. http://digitalcommons.wku.edu/theses/694.
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Bile acids are C24 steroids that are derived in the liver from cholesterol and secreted into the intestinal lumen to aid in emulsification of dietary lipids and lipid-soluble vitamins. The indigenous intestinal microflora modify bile acids, producing up to 20 unique bile acid metabolites. The 7α-dehydroxylation of the bile acids is the most physiologically important bile acid biotransformation. All known intestinal bacteria capable of bile acid 7α-dehydroxylation are anaerobic, gram-positive rods of the genera Clostridium and Eubcicterium. Bile acid 7α-dehydroxylating bacteria often contain bile salt hydrolase, which hydrolyzes the peptide bond in taurine-conjugated bile acids to yield a free bile acid and taurine. Taurine is an organosulfonate containing a sulfite moiety. There have been no published reports indicating whether 7α-dehydroxylating bacteria can utilize taurine. Given that taurine and taurine-conjugated bile acids are found at great concentrations in the intestine, the ability to utilize the compound would confer a competitive advantage to these bacteria. In this study, the ability of 7α-dehydroxylating bacteria to dissimilate taurine and taurine-conjugated bile acids produce hydrogen sulfide was investigated. First, hydrogen sulfide produced by bile acid 7α-dehydroxylating bacteria cultured in tryptic soy broth and semi-defined media from taurine and taurine-conjugated bile acids was qualitatively detected by inclusion of ferric ammonium citrate in the media. The results obtained from trials utilizing anaerobic tryptic soy broth and from semi-defined medium were not consistent, suggesting that qualitative determination of sulfide by inclusion of ferric ammonium citrate is inconclusive. Then hydrogen sulfide produced by bile acid 7α-dehydroxylating bacteria cultured in modified semi-defined medium (not containing a reducing agent) over time in the presence or absence of taurine-conjugated bile acids was quantified using the methylene blue method. Sulfide concentrations in medium cultured with two different strains of bile acid 7α-dehydroxylating bacteria, Eubcicterium sp. 12708 and Clostridium sp. HD-17, in presence of 100 |j.M or 5 mM sulfonates were not significantly higher than those in the absence of sulfonate. In addition, the highest sulfide concentration determined from medium cultured with two different strains of bile acid 7α-dehydroxylating bacteria for a period of five days was not above backgroud level. These data demonstrated that these two bile acid 7α-dehydroxylating bacteria, Eubcicterium sp. 12708 and Clostridium sp. HD-17, are not capable of desulfonating taurine and taurineconjugated bile acids to produce hydrogen sulfide under the conditions tested.
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Werry, Brian Scott. "Characterizing Bile Acid Association as a Ligand and in Micellization." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1386186690.
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Ellis, Ewa C. S. "Use of primary human hepatocytes for elucidation of bile acid synthesis /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-424-0.
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Neilands, Jessica. "Acid tolerance of Streptococcus mutans biofilms /." [Malmö, Sweden] : Malmö University, Faculty of Odontology, Department of Oral Biology, 2007. http://www.mah.se/muep.
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Donnellan, Clare Fiona. "Gene expression in oesophageal cells following acid and bile exposure." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432643.
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Fitzpatrick, W. J. F. "Intrajejunal bile acid precipitation in health and following ileal resection." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599061.
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Hurley, J. P. "Novel bile acid-hydrogel systems as potential nedical device biomaterials." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269055.
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Chaudhury, Saima. "The effect of ispaghula husk upon faecal bile acid excretion." Thesis, London South Bank University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367902.
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Wertheim, Betsy Chaitkin. "Physical Activity as a Determinant of Fecal Bile Acid Levels." Thesis, The University of Arizona, 2008. http://hdl.handle.net/10150/193380.
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Physical activity is protective against colon cancer, whereas colonic bile acid exposure is considered a risk factor. However, the relationship between physical activity and bile acid levels has not been well studied. A cross-sectional analysis of fecal bile acid levels was conducted for 735 colorectal adenoma formers of the ursodeoxycholic acid chemoprevention trial. Hours of recreational activity was found to be inversely related to total fecal bile acid concentrations among participants with low triglycerides, but not for those with high triglycerides. The distinct effects of physical activity between individuals with low versus high triglycerides are suggested to be related to changes in bile acid metabolism, as people with high triglycerides are more likely to have impaired bile acid absorption, thereby increasing bile acid excretion. These results suggest that the protective effect of physical activity may be mediated through decreased colonic bile acid exposure, but only in individuals with low triglycerides.
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Tierney, Juliann Jude. "The synthesis and testing of novel cholic acid based stationary phases." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247854.
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Kaya, Yasemin. "Study of the baiE Gene in Bile Acid 7α-Dehydroxylating Bacteria." TopSCHOLAR®, 1998. http://digitalcommons.wku.edu/theses/315.
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Intestinal bile acid 7α-dehydroxylating bacteria have recently been implicated in cholesterol allstone disease. Eubacterium sp. V.P.I. 12708, a bile acid 7α-dehydroxylating bacterium, contains multiple bile acid inducible (bai) genes which encode the enzymes responsible for bile acid 7a-dehydroxylation. The baiE gene encodes a bile acid dehydratase activity in Eubacterium sp.V.P.I. 12708. Using the polymerase chain reaction assay we determined the presence or absence of baiE-like genes in five clostridial bile-acid 7α-dehydroxylating strains: Clostridium sp. TO-931, Clostridium sp. HD-17, Clostridium sp. TN-271, Clostridium bifermentans 1-55, and Clostridium sordellii ATCC 9714. Results from all the strains tested showed amplification at the predicted DNA fragment size. Partial DNA sequence analysis of the amplified baiE-like genes revealed 88-95% homology with the baiE gene of Eubacterium sp.V.P.I. 12708. These data suggest that baiE-like genes are present in the five bile acid 7α-dehydroxylating strains studied.
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David, Michael. "Study of the baiG Gene in Bile Acid 7α-Dehydroxylating Bacteria." TopSCHOLAR®, 1999. http://digitalcommons.wku.edu/theses/747.
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Recently, intestinal bile acid 7α-dehydroxylating bacteria have been implicated in cholesterol gallstone disease. Eubacterium sp. strain V.P.I. 12708, a bile acid 7α-dehydroxylating bacteria, contains multiple bile acid inducible (bai) genes which are located on a large bai operon. Genes of this operon encode the enzymes responsible for bile acid 7α-dehydroxylation. The baiG gene encodes a bile acid transporter in Eubacterium sp. strain V.P.I. 12708. Utilizing the polymerase chain reaction I determined the presence or absence of baiG-like genes in six bile acid 7α-dehydroxylating strains: Clostridium sp. Strain TN-271, Eubacterium sp. strain 1-10, Clostridium bifermentans strain 1-55, Clostridium sordellii strain Y67, Clostridium sp. strain HD-17, and Clostridium sp. strain TO-931. Results showed amplification in two of the bacterial strains at the predicted DNA fragment size. Partial DNA sequence analysis of the amplified baiG-like gene fragments revealed 96-97% homology with the baiG gene of Eubacterium sp. strain V.P.I. 12708. These data suggest that baiG-like genes are present in Clostridium sp. strain TN-271 and Eubacterium sp. strain I-10.
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Gälman, Cecilia. "Modulation of bile acid and cholesterol metabolism in health and disease /." Stockholm ; Karolinska institutet, 2004. http://diss.kib.ki.se/2004/91-7349-948-x.
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Styles, Nathan Allen. "The characterization of the subcellular localization of bile acid CoA:N-acyltransferase." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2007p/styles.pdf.
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Liu, Ju-Ling. "A conserved bile acid biosynthesis and secretion pathway in Caenorhabditis elegans." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117035.
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The clk-1 mutants of the nematode Caenorhabditis elegans display a highly pleiotropic phenotype that includes an average slowing down, and deregulation of a number of physiological processes, including embryonic and post-embryonic development, aging, and several rhythmic behaviors. clk-1 encodes a conserved enzyme that is necessary for the biosynthesis of ubiquinone (coenzyme Q), a lipid-like molecule that functions as a transporter of electrons in the respiratory chain. One of the features affected in clk-1 mutants is the defecation cycle. Several defecation suppressors of clk-1 genes (dsc) were identified. DSC-4/MTP encodes the worm homolog of the Microsomal Triglyceride Transfer Protein (MTP), a protein whose activity in vertebrates has been found to be crucial for the formation and secretion of ApoB-containing lipoproteins, such as LDL. DSC-3/TAT-2 is a worm homologue of ATP8B1, a flippase that is required for normal bile acid secretion in mammals. By studying these mutants, we found that C. elegans synthesizes and secretes cholesterol-derived molecules with properties and functions resembling those of mammalian bile acids, and that the defecation phenotype of clk-1 mutants is due to altered levels of these bile acid like-molecules resulting from increased mitochondrial oxidative stress in these mutants. As mammalian bile acids function as steroid hormones that mediate lipid, energy and glucose metabolism, our finding that the biology of bile acid–like molecules is regulated by oxidative stress provides a new hypothesis for the significance of oxidative stress in metabolic diseases.Chez le nématode Caenorhabditis elegans, les mutants du gène clk-1 montre un large éventail de défauts phénotypiques incluant un ralentissement de leur développent, un grand nombre de dérégulations physiologiques comme le développement embryonnaire et post embryonnaire, et le vieillissement, ainsi que certains comportements. Le mutant clk-1 code pour une enzyme, évolutionnairement conservée, nécessaire à la biosynthèse de l'ubiquinone (coenzyme Q), une molécule proche des lipides, qui intervient dans le transport des électrons dans la chaine respiratoire. Le mutant clk-1 montre un défaut du comportement de défécation. Nous avons identifié de nombreux gènes supprimant ce phénotype, que nous avons nommés dsc (defecation suppressors of clk-1). DSC-4/MTP est l'homologue de MTP (Microsomal Triglyceride Transfer Protein) chez les vertébrés, une protéine essentielle à la formation et à la sécrétion des lipoprotéines qui contiennent l'apolipoprotéine B, comme les LDL. DSC-3/TAT-2 est une homologue de l'ATP8B1, une flippase requise lors de la sécrétion des acides biliaire chez les mammifères. L'étude de ces deux mutants révèle que C. elegans synthétisent et sécrètent des molécules dérivées du cholestérol dont les fonctions et les propriétés ressemblent à celles des acides biliaires chez les mammifères. De plus, les défauts de la défécation chez les mutant clk-1 sont dus à une altération de ces molécules provenant de l'augmentation du stress oxydatif mitochondrial. Chez les mammifères, les acides biliaires fonctionnent comme des hormones stéroïdes qui régulent les lipides, le métabolisme du glucose, et l'énergie de la cellule. La régulation par le stress oxydatif de ces molécules nous permet donc d'établir de nouvelles hypothèses sur l'importance du stress oxydatif dans la maladie qui affectent le métabolisme.
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Aldhahrani, Adil Abdullah. "Studies on the pathophysiology of bile acid-induced inflammatory airways disease." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3949.
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Background: Gastro-oesophageal reflux and aspiration may be associated with airway disease. Bile acid aspiration has been shown to be prevalent among patients with advanced airway disease, which raises the concern that recurrent microaspiration of bile acids may cause airway epithelial injury which may lead to inflammatory airway disease. Objectives: To investigate the possible links between bile acids and lung injury which may cause pro-inflammatory cytokine release using BEAS- 2B, NCI-H292, 16HBE14o- and Calu-3 cell lines. Moreover, this study aimed at exploring whether primary bronchial epithelial cell cultures taken from lung transplant patients (PHBECs), tracheal epithelial cells (upper airway cells) from the subglottic area cells, BEAS-2B and 16HBE14o- cell lines undergo EMT like processes after stimulation with primary and secondary bile acid. Finally, the role of duodeno-gastro-oesophageal refluxate in mucus production from NCI-H292 and Calu-3 cell lines was investigated. Methods: BEAS-2, 16HBE14o-, NCI-H292 and Calu-3 cell lines were cultured and stimulated with Bile acid (BAs). Pro-inflammatory markers including IL-8, IL-6 and GMCSF were measured. Primary bronchial epithelial cell cultures taken from lung transplant patients and tracheal epithelial cells from the subglottic area cells were cultured. The effect of individual primary and secondary bile acids were evaluated by 48 hour challenge. Post-challenge TGFβ1, MMP9 and pro-collagen concentrations were measured using commercial ELISAs. RNA was isolated to determine the changes in expression of an epithelial marker E-cadherin and the mesenchymal marker fibronectin at a molecular level using a quantitative real-time PCR. The NCI-H292 and Calu-3 cell lines were also used as an in vitro model system to study MUC gene regulation. Cells were stimulated with bile acids and mucin content of the culture medium measured using an indirect ELISA and quantitative real-time PCR was used to evaluate MUC5AC and MUC5B expression in NCI-H292 and Calu-3 cell lines. ii Results: The cells used in this study elevated levels of IL-8, IL-6 and GMCSF released after treatment by primary and secondary bile acids. IL-8, IL-6 and GM-CSF are common finding in airways and lung disease where reflux and aspiration have been implicated as a possible injury. Significantly greater concentration of TGFβ1, MMP9 and pro-collagen were measured in cultures of PHBEs, tracheal epithelial cells, BEAS-2B and 16HBE14o- cell lines treated with BAs. E-cadherin expression significantly decreased while fibronectin was significantly increased. MUC5AC and MUC5B levels were induced in response to stimulation of Calu-3 and NCI H292 cells with BAs. Conclusion: The NCI-H292, Calu-3, BEAS-2B and 16HBE14-o cell lines are sensitive and useful models to study human respiratory processes and diseases related to BAs aspiration-induced lung injury. Aspiration of bile acids may cause cell injury, inflammation and cell death relevant to the pathophysiology of chronic airways disease. Furthermore, Bile acids stimulated EMT related processed in PHBEC, tracheal epithelial cells, BEAS-2B and 16HBE14O-cell lines. The Calu-3 and NCI H292 cells can be used as an in vitro model system to study MUC5AC and MUC5B gene regulation.
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Dempster, Andrew William. "The antimicrobial and bile acid mediated control of Clostridium difficile infection." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52418/.
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Clostridium difficile is an anaerobic, Gram-positive, endospore forming bacillus and is the leading cause of nosocomial infection. Symptoms range from mild diarrhoea to the potentially fatal intestinal complications pseudomembranous colitis and toxic megacolon. The prerequisite for C. difficile infection (CDI) is the perturbation of the healthy microbiota of the gut by broad spectrum antibiotics. It is therefore important to develop therapies which take this in to account, either by minimal disruption of the resident gut microbiota, or by reinstating the protective nature of the gut microbiota. The novel antimicrobial fidaxomicin (FDX) is the first in a new class of macrocyclic antibiotics, with a narrow spectrum of activity for C. difficile. FDX exerts its bactericidal activity by binding to RNA polymerase (RNAP) and inhibiting transcription. The minimum inhibitory concentrations were determined for six clinically relevant isolates of C. difficile and the effect of the drug on spore germination and outgrowth was assessed. Inhibition of C. difficile occurs at low concentrations (0.03 – 0.05 μg/mL) and it was found that FDX does not inhibit the initiation of spore germination, but effectively halts outgrowth at an early stage. The effect of mutations in the β subunit of RNAP were also investigated in terms of susceptibility to FDX and any potential fitness costs incurred to the bacterium. Three separate single nucleotide polymorphisms (SNPs), T3428A, T3428G, G3427T, in the rpoB gene were found to confer reduced susceptibilities to FDX. However, the clinical relevance of these mutations is unclear, as mutants appeared to be attenuated in terms of growth, toxin production and virulence in the hamster model of infection. Clostridium scindens is a member of the healthy gut microbiota and is thought to be a key organism in providing colonisation resistance against C. difficile. C. scindens is the most active transformer of primary bile acids to secondary bile acids, known to inhibit the growth of C. difficile. This occurs due to the gene products of the bile acid inducible operon and a presently unknown reductive arm of the pathway. An RNA extraction protocol for high quality total RNA from C. scindens was developed to aid in the study of the transcriptome of C. scindens cultured with the primary bile acid, cholic acid (CA). This has enabled the identification of potential gene candidates for the reductive arm of the bile transformative pathway of C. scindens. To further study these potential genes, the ability to transfer DNA in to C. scindens is desirable in order to create gene knock outs. The genome of C. scindens ATCC 35704 was assembled and annotated and used to identify potential barriers to DNA transfer. The methylation pattern of this strain identified two type I, twelve type II and one type IV restriction methylation (RM) systems. RM systems were further characterised in an effort to circumvent the RM system barrier to DNA transfer.
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Slabbert, R. S. "Acid tolerance and organic acid susceptibility of selected food-borne pathogens." Interim : Interdisciplinary Journal, Vol 13, Issue 2: Central University of Technology Free State Bloemfontein, 2013. http://hdl.handle.net/11462/296.
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Published ArticleThe development of tolerance to low pH levels and the existence of cross-resistance may promote survival of bacteria in acidic foodstuff and in acidic environments such as the human stomach, in so doing escalating the probability of food poisoning. Similar to antimicrobial resistance developing, there is growing concern that effectiveness of organic acids may decrease as a result of the emergence of acid-tolerant food-borne pathogens. The objectives of this study were to determine the development of acid tolerance in selected food-borne pathogenic bacteria and to explore the activity of organic acids against acid tolerant pathogens. Bacterial strains were screened for acid-tolerance and susceptible strains were induced through exposure to increasing concentrations of an inorganic acid, as well as acidic foodstuffs. Susceptibility to six organic acids at various pH levels was assessed in order to evaluate the possible relationship between altered antimicrobial activity and acid tolerance. Salmonella enterica sv. Enteritidis ATCC 13076 and Escherichia coli ATCC 25922 were found to rapidly develop acid tolerance, while intrinsic acid tolerance was noted in Salmonella enterica sv. Typhimurium ATCC 14028. Pseudomonas aeruginosa ATCC 27853 demonstrated intermediate intrinsic acid tolerance. As expected, pH played a significant role in inhibitory activity of the organic acids as these compounds exhibit optimum antimicrobial activity at a lower pH (pH ≤5). It is, however, necessary to further elucidate the two-way role of pH in foodstuff concomitant to the addition of an organic acid.
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Elderedge, Emelyn R. "Molecular, cellular and regulatory characterization of cholesterol 7#alpha#-hydroxylase." Thesis, University of Edinburgh, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328759.
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Jiang, Zhao-Yan. "Studies on cholesterol and bile acid metabolism in Chinese cholesterol gallstone patients." Stockholm, 2010. http://diss.kib.ki.se/2010/978-91-7409-844-0/.
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Modica, Salvatore. "Intestinal nuclear bile acid receptor FXR activity and regulation in colorectal cancer." Thesis, Open University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520777.
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Duncan, Kenneth William. "Development of a synthetic methodology towards novel bile acid and cholesterol analogues." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248838.
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Kandell, Risa Lynne. "Bile acid-induced DNA damage and repair in bacterial and mammalian cells." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/184976.
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Colon cancer is the second most common type of cancer in the United States. Its incidence is linked epidemiologically to high levels of bile acids in the feces. Bile acids have been implicated as promoters and cocarcinogens in the etiology of colon cancer and as comutagens and mutagens in bacteria. These observations suggest the hypothesis that bile acids may damage DNA. By using the DNA-damage inducible SOS system in Escherichia coli, this study shows that when bacteria are exposed to bile acids there is induction of the SOS repair system and preferential survival of cells undergoing repair. Additionally, differential killing assays using repair defective bacteria show strains defective in recombinational repair or excision repair have lower survival when treated with bile acids than their parental wild-type counterparts. Human fibroblasts were treated with bile acids and unscheduled DNA synthesis (UDS) was measured. UDS is considered to represent the DNA synthesis step in excision repair. UDS, measured by autoradiography, was found to significantly increase in human fibroblasts upon treatment with bile acids. In addition, differential cytotoxicity assays with Chinese Hamster Ovary cells showed that different DNA-repair pathway defective cells were sensitive to different bile acids. Introduction of DNA damage and induction of DNA-repair by bile acids implicates them as possible direct carcinogens in the etiology of colon cancer.
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Sekiguchi, Yusuke. "Structural and functional studies of the Apical Sodium Dependent Bile Acid Transporter." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/30646.
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The apical sodium dependent transporter (ASBT) is responsible for the uptake of bile acids from the apical membrane of the ileum cell. Loss of function mutations of ASBT relate to several diseases, such as Crohn's disease and Primary Bile Acid Malabsorption (PBAM). It is also a target for drugs aimed at lowering cholesterol. The X-ray crystal structure of a bacterial homologue of ASBT, ASBTNM, was previously solved at 2.2Å. In order to understand mechanism of ASBT transport in more detail, further structural and functional information are required. In this thesis, a proteoliposome transport assay was performed for various mutations of residues in the sodium and substrate binding sites. ASBTNM has two sodium binding sites and the residues involved in the sites are functionally important. Both E260A and Q77A showed significantly lower transport activities compared to wild type at 40% and 60% respectively. E260 binds to one sodium ion and Q77 the other. The X-ray crystal structures of these two ASBTNM mutants were solved at 2.9 Å and 3.2 Å respectively. These mutant structures revealed that no large scale conformational changes from the wild type were observed though the mutations clearly affected sodium ion binding. These structural and functional data suggest that both two sodium ions are important for the transport activity of ASBTNM. However even without sodium ions in the binding sites, the protein can take the same conformation as the wild type structure. The data presented in this thesis, together with a comparison with the results from another bile acid transporter that was recently solved, and a homology model of human ASBT, provide insight into the transport mechanism of ASBT.
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Itoh, Shinji. "Roles of βklotho in the negative feedback regulation of bile acid synthesis." Kyoto University, 2005. http://hdl.handle.net/2433/144721.
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Krähenbühl, Stephan. "Impaired bile acid transport in an animal model of defective debrisoquine hydroxylation /." [S.l : s.n.], 1985. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Sagar, Nidhi. "Describing the gut microbiome and metabolomic changes in bile acid diarrhoea (BAD)." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/101543/.
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The diagnosis of BAD is often missed or misdiagnosed for IBS-D as these conditions present similarly with chronic diarrhoea. The principal hindrance to diagnosis of BAD is limited access to the diagnostic SeHCAT scan. Mechanisms of aetiology underlying BAD have not been fully elucidated and to date, an alternative biomarker for BAD that is more accessible and patient preferable, has yet to make its way into clinical practice. One of the greatest scientific challenges this decade has been understanding the relationship between the gut microbiome, its functionality and role in human health. BAs are metabolised by the gut microbiota, therefore their role as signalling molecules in regulating intestinal homeostasis is influenced primarily by the gut commensals. This thesis is the first study to profile the gut microbiome in BAD and investigate the mechanisms of how bacterial metabolic products may influence the development of disease. This was achieved by conducting 16S ribosomal RNA gene analysis, the most important target of study in bacterial ecology. Bacterial metabolites (SCFAs and VOCs) and BAs were measured using gas and liquid chromatography, mass and ion mobility spectrometry. The results indicate intestinal dysbiosis with reduced bacterial diversity in patients with BAD. A statistically significantly greater total concentration of SCFAs with increases in the concentrations of acetate and propionate were observed in BAD compared to IBS-D. A statistically significant increase in the concentrations of faecal primary BAs and serum CDCA was observed in BAD compared to IBS-D. Separation of VOC profiles was evident between the BAD, IBS-D and HC groups but greatest discrimination was between the IBS-D and HC cohorts. In conclusion, intestinal dysbiosis with altered fermentation and resultant BA dysmetabolism were observed. The metabolic output of the microbiota rather than abundance of specific bacterial taxa appears to be more important in the aetiology of BAD.
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Harris, Spencer. "Discovery and characterization of bile acid and steroid metabolism pathways in gut-associated microbes." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4713.
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The human gut microbiome is a complex microbial ecosystem residing in the lumen of our gastrointestinal tract. The type and amounts of microbes present in this ecosystem varies based on numerous factors, including host genetics, diet, and environmental factors. The human gut microbiome plays an important role in normal host physiological functions, including providing energy to colonocytes in the form of short-chain fatty acids. However, gut microbial metabolites have also been associated with numerous disease states. Current tools for analyzing the gut microbiome, such as high-throughput sequencing techniques, are limited in their predictive ability. Additionally, “-omic” approaches of studying the complex array of molecules, such as transcriptomics (RNA), proteomics (proteins), and metabolomics (previously identified physiologically active molecules), give important insight as to the levels of these molecules but do not provide adequate explanations for their production in a complex environment. With a better physiological understanding of why specific metabolites are produced by the gut microbiome, more directed therapies could be developed to target their production. Therefore, it is immensely important to study the specific bacteria that reside within the gut microbiome to gain a better understanding of how their metabolic actions might impact the host. Within this framework, this study aimed to better understand the production of secondary bile acid metabolites by bacterial in the gut microbiome. High levels of secondary bile acids are associated with numerous pathophysiological disorders including colon cancer, liver cancer, and cholesterol gallstone disease. In the current study, three bile acid metabolizing strains of bacteria that are known members of the gut microbiome were studied. A novel strain of Eggerthella lenta was identified and characterized, along with the type strain, for its ability to modulate bile acid and steroid metabolism based on the atmospheric gas composition. Additionally, it was shown that the oxidation of hydroxyl groups on primary bile acids by E. lenta C592 inhibited subsequent 7α-dehydroxylation by Clostridium scindens. The gene involved in the production of a Δ4,6-reductase enzyme, responsible for catalyzing two of the final reductive steps in the 7α-dehydroxylation pathway, was putatively identified and characterized in Clostridium scindens ATCC 35704. Lastly, the transcriptomic profile of Clostridium scindens VPI 12708 in the presence of numerous bile acids and steroid molecules was studied. These studies contribute significantly to the understanding of why specific bile acid metabolites are made by members of the gut microbiome and suggest ways of modulating their production.
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Jesus, Cláudia Marisa de. "Salicylic acid and drought tolerance improvement in Eucalyptus." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13377.
Full textAbstract:
Mestrado em Biologia AplicadaCovering approximately 20 million ha, Eucalyptus genus is the most widely planted hardwood trees all over the world. In the Mediterranean region, the positive performance of Eucalyptus plantations is conditioned by low water availability that strongly limits forest productivity and alters plant growth and development. Plant drought tolerance can be managed by adopting strategies such as exogenous application of hormones. Salicylic acid (SA) is a plant endogenous regulator of growth (PGR) that has been reported as a compound playing a key role in plants responses to drought. In this study, we investigated if the exogenous application of SA improves drought tolerance on E. globulus and how this treatment regulates plant response to stress. SA was applied by foliar application of 0.75, 2.5 and 5 mM solution of sodium salicylate three consecutive days before water-stress (WS) induction (plants daily watered at 15% field capacity). Additionally a well-watered group (WW, daily watered at 70%) was analysed, with the same SA pre-treatments. Control plants (WW and WS) were not treated with SA. The assessed morpho-physiological and biochemical traits were: water potential, lipid peroxidation, pigments content, total soluble sugars, phenols, Fv/Fm, gas exchange and contain of different PGRs (abscisic acid, ABA; indolacetic acid, AIA; dihydrozeatin riboside, DHZ; gibberellin GA4; isopentenyl adenine, IP; jasmonic acid, JA; salicylic acid, SA). Specific local dynamics of IAA and ABA in leaves was detected by their immunolocalization. The results showed that drought stress severely affected the plant physiology. On the other side, the performance of plants under water-stressed conditions showed a significant improvement after the foliar application of SA. Global quantification of PGRs didn’t show great differences between treatments, with the exception of SA, however local distribution of IAA and ABA in leaves was clearly affected. The efficiency of exogenous SA depended on the applied dose, with 5 mM being more effective to induce the drought tolerance. These positive effects were highlighted in water potential, gas exchange (CO2 assimilation rate) and lipid peroxidation. In the current global changes SA treatment could be very useful in breeding forest programs and can effectively ameliorate the negative effect of drought stress in Eucalyptus plants.
Eucalyptus é um dos géneros florestais mais plantados em todo o mundo, contabilizando aproximadamente um total de cerca de 20 milhões de hectares. Na região do Mediterrâneo, o desempenho das plantações de eucalipto é condicionado pela baixa disponibilidade de água que limita fortemente a produtividade florestal, afetando o crescimento e desenvolvimento das plantas. O desenvolvimento de plantas tolerantes à seca pode ser conseguido através da adoção de estratégias de mitigação como a aplicação exógena de hormonas. O ácido salicílico (AS) é um regulador endógeno do crescimento de plantas, amplamente referido como um composto chave na resposta das plantas à seca. Neste estudo, investigamos se a aplicação exógena de SA melhora a tolerância à seca em Eucalyptus globulus e de que forma este tratamento regula a resposta da planta ao défice hídrico. AS foi aplicado por aplicação foliar de solução de salicilato de sódio nas concentrações de 0.75, 2.5 e 5 mM, três dias consecutivos antes da indução de stress hídrico (plantas mantidas a 15 % da capacidade de campo). Além disso, um grupo bem regado (diariamente regado a 70 % da capacidade de campo) foi analisado, com os mesmos pré-tratamentos de AS. Plantas controlo (15 e 70 %) não foram tratadas com AS. As características morfo-fisiológicas e bioquímicas foram avaliadas através dos seguintes parâmetros: potencial hídrico, peroxidação lipídica, conteúdo de pigmentos fotossintéticos, açúcares solúveis totais, fenóis, Fv/Fm, trocas gasosas e conteúdo de diferentes hormonas (ácido abscísico, ABA; ácido indol-3-acético, AIA; dihidrozeatina, DHZ; giberelina GA4; isopentenil adenina, IP, ácido jasmónico, JA; ácido salicílico, SA). Dinâmicas locais específicas do AIA e ABA nas folhas foram detetadas por imunolocalização. Os resultados mostraram que a seca afetou a fisiologia da planta. Por outro lado, o desempenho das plantas sob condições de stress hídrico apresentaram uma melhora significativa após a aplicação foliar de AS. A quantificação global de hormonas mostrou diferenças significativas entre os tratamentos hídricos, com o aumento das hormonas ABA e JA em plantas sob défice hídrico. Relativamente aos tratamentos com AS, as plantas sob défice hídrico mostraram diferenças nas hormonas DHZ, GA4 e IP. A distribuição local de AIA e ABA nas folhas foi claramente afetada pela indução de stress hídrico. A eficiência da aplicação foliar do AS depende da dose aplicada, com a concentração 5 mM a mostrar-se mais eficaz na indução da tolerância à seca. Estes efeitos positivos foram destacados no potencial hídrico, na taxa de assimilação de CO2 e na peroxidação lipídica. Nas atuais mudanças globais, o tratamento AS poderá ser muito útil nos programas de melhoramento florestal, podendo efetivamente melhorar o efeito negativo do défice hídrico em plantas de eucalipto.
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Reeve, Wayne. "The molecular basis of acid-tolerance in Rhizobium." Thesis, Reeve, Wayne (1995) The molecular basis of acid-tolerance in Rhizobium. PhD thesis, Murdoch University, 1995. https://researchrepository.murdoch.edu.au/id/eprint/41087/.
Full textAbstract:
The aim of this study was to investigate the molecular basis of acidtolerance in Rhizobium. Transposon Tn5-induced mutants were used to identify genes required for acid-tolerance in the Sardinian strain Rhizobium meliloti WSM419 and the Japanese strainR. leguminosarum bv. viceae WSM710. Plant inoculation tests showed that nodulation by these acid-sensitive mutants on their respective hosts was comparable to that of the wild-type.
Calcium affected the growth of both wild-type Rhizobium strains at acidic pH. Cells of R. meliloti WSM419 grew faster at acidic pH and could grow at a progressively lower pH as the calcium concentration was increased. R.
leguminosarum WSM710 was able to grow below pH 4.9 if the concentration of calcium was increased in the medium. The acid-sensitive mutants could be divided into two groups on the basis of their response at acidic pH to the external calcium concentration. The first group (R. meliloti strains TG 1-6, TG 1-11, TG2-6, TGS-46 and R. leguminosarum WR6-35) grew at low pH if extra calcium was supplied in the medium. In the second group were those mutants (R. meliloti RT3-27 and R. leguminosarum WRl-14) that were unable to grow at low pH even if a high concentration of calcium was supplied.
Southern hybridisation studies using Tn5 as a probe demonstrated that each mutant contained only a single copy of Tn5. The re-insertion of Tn5 back into the wild-type using a suitable site-directed homologous recombination strategy (with an appropriate suicide vehicle for R. meliloti or phage RL38 mediated transduction for R. leguminosarum) recreated the acid-sensitive phenotype which verified that Tn5 was the causative agent of the disruption of a gene required for acid-tolerance.
The rhizobial DNA flanking Tn5 was cloned from the mutants TG2-6, TGS-46, RT3-27, WR6-35, and WRl-14 and the DNA was sequenced and analysed for protein encoding regions. DNA or protein sequences were then used to search for similarity in the GenBank, EMBL, or GenPeptide databases. The genes interrupted by Tn5 in the mutants were designated as act genes (acidtolerance genes) and numbered according to the name of the mutant; for example, the gene disrupted by Tn5 in TG2-6 was labelled as act206.
The predicted protein (Act206) encoded by act206 in WSM419 is 541 amino acids in length and has an estimated molecular weight of 57, 963 D and a pl of 9.0. An incomplete open reading frame contiguous to act206 appears to code for a DNA binding protein homologous to URF4 of Rhodospirillum rubrum and n~pressors in coliphage. The Act206 protein has a small degree of identity (30 % over 465 amino acids) but higher similarity (69 % over 465 amino acids) to CutE from Escherichia coli. Disruption of the latter protein caused a copper sensitive phenotype in cells of E. coli. S. typhimurium also contains an allele of cutE which, if mutated, causes a temperature-sensitive and copper-sensitive phenotype and a reduction in the activity of the lipid metabolising enzyme apolipoprotein Nacy ltransferase. The act206 mRNA was found in cells grown under both acidic (pH 5.8) and neutral (pH 7.0) conditions. The act206 gene appears to be chromosomal and was found in all seven strains of R. meliloti examined. At this stage the role of Act206 in acid-tolerance remains unclear.
The gene inactivated in WR6-35 has a strong similarity to the exoR sequence of R. meliloti Rm1021 (71.3 % over 892 bp). The protein (Act635) encoded by act635 is predicted to be 267 amino acids in length with a molecular weight of 28, 920 D and a calculated pl of 5.5. The Act635 protein has 93.3 % similarity and 70 % identity over 267 amino acids with R. meliloti Rm1021 ExoR. Strain WR6-35 produced approximately twice as much EPS as the wild-type WSM710 under the conditions used. NMR spectra of EPS produced by the wildtype and WR6-35 were indistinguishable. Disruption of exoR in R. leguminosarum caused a mildly acid-sensitive phenotype; one possible explanation is that a perturbation of the cytoplasmic membrane has resulted through an overproduction of EPS which subsequently caused an increased susceptibility to proton influx. The gene disrupted by Tn5 in R. meliloti TG5-46 (actR; previously called act546) encodes a protein (ActR) of 193 amino acids with a predicted molecular weight of 21, 463 D and a pl of 8.3. This protein has a similar amino-terminal region to regulatory proteins of the histidine protein kinase/regulator protein family involved in signal transduction in bacteria. ActR has a high degree of similarity over the entire protein sequence of PrrA from Rhodobacter capsulatus (94.9 % similarity, 69.3 % identity over 176 amino acids). It also had a high degree of similarity with RegA from Rhodobacter capsulatus (92.6 % similarity, 70.5 % identity over 176 amino acids) or R. sphaeroides (92.6 % similarity, 67.0 % identity over 176 amino acids). Neither, PrrA or RegA belong to any recognised subclass ofregulators and hence have been classified in a new subgroup. It is postulated that ActR falls into this new subgroup based on protein similarity. The predicted protein encoded by the gene upstream to actR showed similarity with sensor proteins, such as PhoR (67.2 % similarity and 24.6 % identity over 244 amino acids) from Escherichia coli and FixL (69.5 % similarity and 25.4 % identity over 256 amino acids) from Bradyrhizobium japonicum, which are members of the histidine protein kinase/regulator family. It is speculated that this protein, consequently labelled as ActS, may play a role in the detection of the hydrogen ion concentration and transfer this signal to ActR which in turn regulates one or more structural genes.
The genes inactivated in R. meliloti RT3-27 (act327) or R. leguminosarum WRl-14 (actl 14) showed similarity with genes which encode P-type ATPases in a variety of eukaryotes and prokaryotes. These genes may encode proteins which have a direct role in proton translocation or an indirect role through ion transport in the cell.
The possible implications of these findings are discussed and a tentative model for the genetic basis of acid-tolerance in Rhizobium is presented.