pH-Dependent Modulation of Cyclic AMP Levels and GadW-Dependent Repression of RpoS Affect Synthesis of the GadX Regulator and<i>Escherichia coli</i>Acid Resistance

Ma, Zhongyou; Richard, Hope; Foster, John W.

doi:10.1128/jb.185.23.6852-6859.2003

Cited by 64 publications

(76 citation statements)

References 22 publications

(43 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Control of this system has been shown to differ depending on the culture conditions (i.e., complex medium or minimal medium), and it involves multiple regulators (13). Under the conditions we used for our studies, specifically growth in LB broth at pH 7.0, gadX mRNA is expressed during stationary phase in a manner that is dependent on the secondary sigma factor S (27).…”

Section: Discussionmentioning

confidence: 99%

GadY, a Small-RNA Regulator of Acid Response Genes inEscherichia coli

2004

View full text Add to dashboard Cite

A previous bioinformatics-based search for small RNAs in Escherichia coli identified a novel RNA named IS183. The gene encoding this small RNA is located between and on the opposite strand of genes encoding two transcriptional regulators of the acid response, gadX (yhiX) and gadW (yhiW). Given that IS183 is encoded in the gad gene cluster and because of its role in regulating acid response genes reported here, this RNA has been renamed GadY. We show that GadY exists in three forms, a long form consisting of 105 nucleotides and two processed forms, consisting of 90 and 59 nucleotides. The expression of this small RNA is highly induced during stationary phase in a manner that is dependent on the alternative sigma factor S . Overexpression of the three GadY RNA forms resulted in increased levels of the mRNA encoding the GadX transcriptional activator, which in turn caused increased levels of the GadA and GadB glutamate decarboxylases. A promoter mutation which abolished gadY expression resulted in a reduction in the amount of gadX mRNA during stationary phase. The gadY gene was shown to overlap the 3 end of the gadX gene, and this overlap region was found to be necessary for the GadY-dependent accumulation of gadX mRNA. We suggest that during stationary phase, GadY forms base pairs with the 3-untranslated region of the gadX mRNA and confers increased stability, allowing for gadX mRNA accumulation and the increased expression of downstream acid resistance genes.

show abstract

Section: Discussionmentioning

confidence: 99%

GadY, a Small-RNA Regulator of Acid Response Genes inEscherichia coli

2004

View full text Add to dashboard Cite

show abstract

“…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).…”

mentioning

confidence: 99%

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

Johnson¹,

Burton²,

Gutiérrez³

et al. 2011

Journal of Bacteriology

View full text Add to dashboard Cite

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...

show abstract

“…Most notable are gadA, encoding an isozyme of glutamate decarboxylase (45,47), and gadE, the essential activator of glutamate-dependent acid resistance (22,30). Two other genes in this region, GadX and GadW, are involved in modulating gadE expression as well as the expression of gadA and gadBC (16,32,33,44,(48)(49)(50)52). However, the contribution of other AFI genes toward acid resistance has remained unclear.…”

mentioning

confidence: 99%

Products of theEscherichia coliAcid Fitness Island Attenuate Metabolite Stress at Extremely Low pH and Mediate a Cell Density-Dependent Acid Resistance

2007

Self Cite

View full text Add to dashboard Cite

Escherichia coli has an ability, rare among the Enterobacteriaceae, to survive extreme acid stress under various host (e.g., human stomach) and nonhost (e.g., apple cider) conditions. Previous microarray studies have exposed a cluster of 12 genes at 79 centisomes collectively called an acid fitness island (AFI). Four AFI genes, gadA, gadX, gadW, and gadE, were already known to be involved in an acid resistance system that consumes an intracellular proton through the decarboxylation of glutamic acid. However, roles for the other eight AFI gene products were either unknown or subject to conflicting findings. Two new aspects of acid resistance are described that require participation of five of the remaining eight AFI genes. YhiF (a putative regulatory protein), lipoprotein Slp, and the periplasmic chaperone HdeA protected E. coli from organic acid metabolites produced during fermentation once the external pH was reduced to pH 2.5. HdeA appears to handle protein damage caused when protonated organic acids diffuse into the cell and dissociate, thereby decreasing internal pH. In contrast, YhiF-and Slp-dependent systems appear to counter the effects of the organic acids themselves, specifically succinate, lactate, and formate, but not acetate. A second phenomenon was defined by two other AFI genes, yhiD and hdeD, encoding putative membrane proteins. These proteins participate in an acid resistance mechanism exhibited only at high cell densities (>10 8 CFU per ml). Densitydependent acid resistance does not require any demonstrable secreted factor and may involve cell contactdependent activation. These findings further define the complex physiology of E. coli acid resistance.

show abstract

pH-Dependent Modulation of Cyclic AMP Levels and GadW-Dependent Repression of RpoS Affect Synthesis of the GadX Regulator andEscherichia coliAcid Resistance

Cited by 64 publications

References 22 publications

GadY, a Small-RNA Regulator of Acid Response Genes inEscherichia coli

GadY, a Small-RNA Regulator of Acid Response Genes inEscherichia coli

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

Products of theEscherichia coliAcid Fitness Island Attenuate Metabolite Stress at Extremely Low pH and Mediate a Cell Density-Dependent Acid Resistance

Contact Info

Product

Resources

About