Regulation of katF and katE in Escherichia coli K-12 by weak acids

Abstract

Chromosomal transcriptional and translational lacZ fusions to the katE (structural gene for the HPII hydroperoxidase) and katF (putative sigma factor required for katE expression) genes ofEscherichia coli were isolated, and the regulation of these fusions was used to identify factors that control the expression of these two important antioxidant factors. While katE was found to be regulated primarily at the level of transcription (since induction patterns were similar for both transcriptional and translational fusions), katF expression was a function of both transcriptional and translational signals. The katE gene was induced 57-fold as cells entered the stationary phase, while katF was induced 23-fold. katF induction was coincident with katE induction and occurred at the onset of the stationary growth phase. Expression of both katE and katF could be induced by resuspending uninduced exponential-phase cells in spent culture supernatant recovered from stationary-phase cells. The component of stationary-phase culture supernatant responsible for induction of the katF regulon appeared to be acetate, since expression of both katE and katF fusions was induced when exponential-phase cells were exposed to this weak acid. Other weak acids, including propionate and benzoate, were also found to be effective inducers of expression of both katF and katE. Induction of katE and katF fusions was unaffected in merodiploid strains containing both mutant and wild-ype alleles, indicating that expression of both genes is independent of the wild-type gene product. Examination of catalase zymograms prepared from cells exposed to various levels of acetate revealed that both HPI and HPII catalases are induced by this weak acid, suggesting that there is a common link in the regulation of these two enzymes.

The Salmonella typhimurium katF (rpoS) gene: cloning, nucleotide sequence, and regulation of spvR and spvABCD virulence plasmid genes

“…However, though the levels of U70 protein were shown to be almost constant throughout the growth phase of E. coli, the levels of the crs protein were found to increase during the stationary phase of growth (42). This growth phase regulation of as involves both transcriptional and posttranscriptional controls and is consistent with the fact that various us-dependent genes are induced during the stationary phase (18,19,22,25,35).…”

Inhibition of Escherichia coli growth by acetic acid: a problem with methionine biosynthesis and homocysteine toxicity

“…The stress-inducible sigma factor, RpoS (σ s ), is known to play an important role in acid tolerance in E. coli (Castanie-Cornet et al, 1999) and it accumulates under conditions of weak-acid stress (Mulvey et al, 1990 ;Schellhorn & Stones, 1992). It was therefore possible that the relief of growth inhibition observed in the presence of methionine was dependent on this sigma factor.…”

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“…In E. coli, an increase of HPI catalase activity in stationary phase, attributed to RpoS-dependent transcription of katG has been reported 18 . In the rpoS mutants, these authors 15 detected little or no catalase activities by zymography assays. In contrast, our results agree with the published reports of Visick and Clarke 21 that observed higher HPI activity in the rpoS mutant (~50%) than in the wild type.…”

“…5). In E. coli the KatE is known to be regulated by RpoS, consequently cellular expression of this enzyme increases at the onset of the stationary phase 14,15 . From the activity gel in Fig.…”