The lactic acid-induced acid tolerance response in Salmonella enterica serovar Typhimurium induces sensitivity to hydrogen peroxide.
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ABSTRACT:
SUBMITTER: Greenacre EJ
PROVIDER: S-EPMC1538734 | biostudies-literature | 2006 Aug
REPOSITORIES: biostudies-literature
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The lactic acid-induced acid tolerance response in Salmonella enterica serovar Typhimurium induces sensitivity to hydrogen peroxide.
Greenacre E J EJ Lucchini S S Hinton J C D JC Brocklehurst T F TF
Applied and environmental microbiology 20060801 8
Transcriptome analyses of Salmonella enterica serovar Typhimurium revealed that 15 genes were significantly up-regulated after 2 h of adaptation with lactic acid. cadB was the most highly up-regulated gene and was shown to be an essential component. Lactic acid-adapted cells exhibited sensitivity to hydrogen peroxide, likely due to down-regulation of the OxyR regulon. ...[more]
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Project description:BACKGROUND: Hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) are reactive oxygen species that are part of the oxidative burst encountered by Salmonella enterica serovar Typhimurium (S. Typhimurium) upon internalization by phagocytic cells. In order to survive, bacteria must sense these signals and modulate gene expression. Growing evidence indicates that the ArcAB two component system plays a role in the resistance to reactive oxygen species. We investigated the influx of H2O2 and HOCl through OmpW and the role of ArcAB in modulating its expression after exposure to both toxic compounds in S. Typhimurium. RESULTS: H2O2 and HOCl influx was determined both in vitro and in vivo. A S. Typhimurium ompW mutant strain (?ompW) exposed to sub-lethal levels of H2O2 and HOCl showed a decreased influx of both compounds as compared to a wild type strain. Further evidence of H2O2 and HOCl diffusion through OmpW was obtained by using reconstituted proteoliposomes. We hypothesized that ompW expression should be negatively regulated upon exposure to H2O2 and HOCl to better exclude these compounds from the cell. As expected, qRT-PCR showed a negative regulation in a wild type strain treated with sub-lethal concentrations of these compounds. A bioinformatic analysis in search for potential negative regulators predicted the presence of three ArcA binding sites at the ompW promoter region. By electrophoretic mobility shift assay (EMSA) and using transcriptional fusions we demonstrated an interaction between ArcA and one site at the ompW promoter region. Moreover, qRT-PCR showed that the negative regulation observed in the wild type strain was lost in an arcA and in arcB mutant strains. CONCLUSIONS: OmpW allows the influx of H2O2 and HOCl and is negatively regulated by ArcA by direct interaction with the ompW promoter region upon exposure to both toxic compounds.
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