RcsB Is Required for Inducible Acid Resistance in Escherichia coli and Acts at gadE-Dependent and -Independent Promoters

Abstract

RcsB interacts with GadE to mediate acid resistance in stationary-phase Escherichia coli K-12. We show here that RcsB is also required for inducible acid resistance in exponential phase and that it acts on promoters that are not GadE regulated. It is also required for acid resistance in E. coli O157:H7.The glutamate-dependent acid resistance system AR2 of Escherichia coli is regulated by a regulatory network that responds to general stress, via the alternative sigma factor RpoS, and to low pH (8,13,17,18,20,22,25). AR2 requires several regulators, including the central regulator GadE, to integrate signals from the EvgAS and PhoPQ two-component systems (3,(10)(11)(12)(13)17). RcsB, a regulator with a wide range of roles in many enteric bacteria (5), is essential for survival during extreme acid challenge (pH 2.5 or below) during stationary phase and regulates transcription of some AR2 genes by forming a heterodimer with GadE (2, 4, 15, 16). RcsB also forms heterodimers with RcsA, TviA, and BglJ to regulate colanic acid synthesis, antigen VI expression, and sugar transport, respectively (26-28). Here we show that the inducible acid resistance of exponential-phase E. coli is also completely dependent on RcsB and that this resistance correlates with dependence of activation of the AR2 network on RcsB. We show that several AR2 genes that are not GadE regulated require RcsB and that RcsB must interact downstream of the sensor kinase EvgS but upstream of the first regulator, YdeO. These results suggest an additional role for RcsB in the activation of acid resistance and show that there is cross talk between the Rcs and EvgAS systems. We show that the role of RcsB extends to the pathogenic strain E. coli O157:H7 (Sakai).Induced acid resistance is rcsB dependent. A ⌬rcsB derivative of E. coli K-12 MG1655 was constructed as previously described (7). We determined the survival of this strain and the wild-type parent to extreme acid challenge in exponential phase, with and without induction by mild acidification (pH 5.7). Both strains grew at the same rate. Cells were grown, from overnight cultures diluted at least 500-fold, to an optical density at 600 nm (OD 600 ) of 0.2 in M9 with glucose (22.2 mM) and Casamino Acids (0.2% [wt/vol]), buffered with morpholinepropanesulfonic acid (MOPS) and morpholineethanesulfonic acid (MES) as described previously (M9supp) (1), and then incubated at pH 5.7 or pH 7 for 70 min before acid challenge at pH 2.4 for 2 h. We determined that under these conditions there are no detectable carryover effects from stationary phase on gene expression or cell survival. Cultures were always checked to ensure that the adjusted pH values remained constant for the entire experiment (data not shown). Survival was measured as previously described (1). Induction at pH 5.7 caused a significant increase in resistance in the wild-type strain (Fig. 1a). Survival of the ⌬rcsB strain was below the level of detection in both induced and uninduced cultures (Fig. 1a). To complement the rcsB deletion, we constructed p...

RcsB Contributes to the Distinct Stress Fitness among Escherichia coli O157:H7 Curli Variants of the 1993 Hamburger-Associated Outbreak Strains

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Combinatorial Strategies for Improving Multiple-Stress Resistance in Industrially Relevant Escherichia coli Strains

“…Elimination of Rfe, catalyzing a step in lipopolysaccharide (enterobacterial common antigen and O antigen) biosynthesis, and RcsB, which is the response regulator of a two-component system involved in activation of capsular colanic acid biosynthesis, likely results in an alteration of cell surface properties. RcsB is also required for EvgS/EvgA activation (71). Other gene products shown in Fig.…”

Alkali Metals in Addition to Acidic pH Activate the EvgS Histidine Kinase Sensor in Escherichia coli

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