1887

Abstract

serovar Typhimurium possesses three similar NiFe hydrogenases important to its virulence. Here we show that the three hydrogenase operons , and are expressed under different environmental conditions and are subject to control by different regulatory proteins. Hydrogenase promoter- fusion plasmids were transferred into the wild-type strain or into , , , and deletion mutants, or into a / double mutant. The promoter had highest -galactosidase activity under growth conditions promoting anaerobic respiration (glycerol plus fumarate) and may be subject to glucose repression, since cells grown with glucose had about half the transcriptional activity of cells grown with mannose. Based on the phenotype of regulatory mutant strains, IscR represses aerobically, and ArcA plays a role in both and regulation. The promoter had about five times more activity in cells grown under aerobic conditions compared to anaerobic levels, and its activity tripled in an mutant grown anaerobically. The promoter had the highest activity when cells were grown anaerobically with glucose, and the growth yield of the mutant was about 25 % lower than for wild-type cells grown fermentatively, suggesting that Hya may be utilized during fermentation. The promoter is repressed by nitrate and this repression was abolished when the NarL-binding site was mutated, or in a mutant background. FNR is involved in and regulation, since -galactosidase activity decreased significantly in a mutant. These findings suggest that the three hydrogenases are used under different conditions, likely enhancing the pathogen's capacity to survive in a variety of environments.

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2007-10-01
2019-10-21
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