Determinants Influencing Polar Flagellar Biosynthesis and Cell Division in Campylobacter jejuni

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Title: Determinants Influencing Polar Flagellar Biosynthesis and Cell Division in Campylobacter jejuni
Author: Balaban, Murat
Abstract: Campylobacter jejuni is a worldwide leading cause of bacterial gastrointestinal disease . The natural habitat of this organism is the gastrointestinal tracts of warm -blooded animals , especially poultry , where the bacterium promotoes a harmless commensal colonization . The abundance of C . jejuni in poultry creates a risk for food -borne infections to human populations . Flagellar motility by C . jejuni is required to colonize both human and animal hosts . For motility , C . jejuni produces amphitrichous flagella , resulting in the formation of a single flagellum at both poles . This work explored factors that regulate numerical and spatial parameters for amphitrichious flagellation . Two factors that have been identified to control flagellar placement and numbers in polarly -flagellated bacteria are the FlhF GTPase and the FlhG ATPase . FlhF has been shown to be required for regulation of flagellar gene expression and flagellar placement in some Pseudomonas and Vibrio species . Characterization of FlhF in C . jejuni was accomplished by creating point mutants in C -terminal GTPase domain of FlhF to decrease its GTPase activity . GTPase mutants , unlike mutants that lack FlhF , did not have a significant reduction in sigma54 -dependent flagellar gene expression . Instead , a significant proportion of the population produced flagella at lateral sites or produced multiple flagella at a pole , whereas wild -type bacteria produced single polar flagella . Further experiments suggested that FlhF functions downstream of the FlgSR -flagellar export apparatus (FEA ) pathway to activate sigma54 -dependent flagellar gene expression . Thus , our data suggested that FlhF and its GTPase activity are required for distinct processes in flagellar gene regulation . FlhG has been shown to control flagellar numbers in Pseudomonas and Vibrio species . We examined flhG mutants and confirmed that FlhG regulates flagellar numbers . C . jejuni flhG mutants also demonstrated a minicell phenotype , which is the result of division erroneously occurring at polar regions . Further examination revealed that FlhG and the flagellar base components compose a novel division inhibition system to spatially prevent polar division and encourage septation at the cellular midpoint for symmetrical division . This work greatly extends our understanding of factors that govern spatial and numerical patterns of polar flagellation and has identified an unprecedented system to spatially regulate division in bacteria .
URI: http : / /hdl .handle .net /2152 .5 /868
Date: 2011-08-18

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Determinants Influencing Polar Flagellar Biosynthesis and Cell Division in Campylobacter jejuni. Graduate School of Biomedical Sciences. Available electronically from http : / /hdl .handle .net /2152 .5 /868 .

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