Global analysis of Escherichia coli gene expression during the acetate-induced acid tolerance response.
The ability of Escherichia coli to survive at low pH is strongly affected by environmental factors, such as composition of the growth medium and growth phase. Exposure to short-chain fatty acids, such as acetate, proprionate, and butyrate, at neutral or nearly neutral pH has also been shown to increase acid survival of E. coli and Salmonella enterica serovar Typhimurium. To investigate the basis for acetate-induced acid tolerance in E. coli O157:H7, genes whose expression was altered by exposure to acetate were identified using gene arrays. The expression of 60 genes was reduced by at least twofold; of these, 48 encode components of the transcription-translation machinery. Expression of 26 genes increased twofold or greater following treatment with acetate. This included six genes whose products are known to be important for survival at low pH. Five of these genes, as well as six other acetate-induced genes, are members of the E. coli RpoS regulon. RpoS, the stress sigma factor, is known to be required for acid tolerance induced by growth at nonlethal low pH or by entry into stationary phase. Disruption of the rpoS gene by a transposon insertion mutation also prevented acetate-induced acid tolerance. However, induction of RpoS expression did not appear to be sufficient to activate the acid tolerance response. Treatment with either NaCl or sodium acetate (pH 7.0) increased expression of an rpoS::lacZ fusion protein, but only treatment with acetate increased acid survival.
Department of Biology, Texas A&M University, College Station, Texas 77843-3258, USA.
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Arnold
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McElhanon
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A
Lee
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Leonhart
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Siegele
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D015870:Gene Expression; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D016366:Open Reading Frames; D018384:Oxidative Stress; D012808:Sigma Factor / Q000502:physiology; D019346:Sodium Acetate / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology
D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D012965:Sodium Chloride; D019346:Sodium Acetate