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dc.contributor.authorBrahmachary, Priyanka Pradeep
dc.description.abstract8054 The human gastric pathogen Helicobacter pylori utilizes all three sigma factors ( 1, 128 54and 1)found in this bacterium for flagellar biogenesis. 1-dependent transcription has an absolute requirement for activator protein which usually binds to enhancer upstream of the 5454promoter and contacts the 1-RNA polymerase holoenzyme ( 1-holoenzyme) bound at the 54 promoter through DNA looping. H. pylori FlgR is a 1-dependent activator that is required for 54expression of the 1-dependent flagellar genes in this bacterium and is part of a two-component regulatory system. FlgS is the cognate sensor kinase of FlgR and is also required for transcription 54of the 1-dependent flagellar genes. FlgR is unusual in that it lacks the DNA-binding domain 5454found in most other 1-dependent activators. Studies using 1-dependent flaB’- åxylE reporter gene constructs in H. pylori demonstrated that 42 bp of DNA upstream of the flaB promoter was sufficient for efficient transcription. Purified FlgR activated transcription from the Salmonella enterica serovar Typhimurium glnA promoter in an in vitro transcription assay. Taken together, these data argue that FlgR does not activate transcription from an enhancer, but rather by 54contacting 1-holoenzyme directly. HP0137 interacts with FlgS in a yeast two-hybrid assay, and inactivation of the gene encoding this protein interfered with flagellar biogenesis. Expression of flaB was unaffected in the hp0137 mutant, suggesting that HP0137 is not required for FlgS function but instead is involved in flagellar assembly. A second project examined the function of a putative acetone carboxylase in H. pylori. Acetone enhanced the growth of a wild-type H. pylori strain but not that of an acxB (encodes . subunit of acetone carboxylase) mutant. Acetone was depleted over the course of several hours by cultures of wild-type H. pylori, but not by cultures of the acxB mutant. Taken together, these observations suggest that H. pylori has a functional acetone carboxylase. The acxB mutant was more sensitive to acetaldehyde, which is structurally similar to acetone, than the parental strain, suggesting that acetone carboxylase has a role in detoxification of acetaldehyde. The acxB mutant was defective in colonization of mice, indicating that acetone carboxylase has an important role in host colonization. 54
dc.subjectHelicobacter pylori FlgR
dc.subjectFlagellar biosynthesis
dc.subjectó54-dependent activator, HP0137
dc.subjectFlagellar export apparatus
dc.subjectAcetone carboxylase, Acetaldehyde
dc.subjectVirulence factor
dc.titleNovel aspects of flagellar biogenesis and virulence in Helicobacter pylori
dc.description.advisorTimothy Hoover
dc.description.committeeTimothy Hoover
dc.description.committeeDuncan Krause
dc.description.committeeEllen Neidle
dc.description.committeeRobert Maier
dc.description.committeeMark Farmer

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