Dataset Information

Decrypting the H-NS-dependent regulatory cascade of acid stress resistance in Escherichia coli.

ABSTRACT:

Background

H-NS regulates the acid stress resistance. The present study aimed to characterize the H-NS-dependent cascade governing the acid stress resistance pathways and to define the interplay between the different regulators.

Results

We combined mutational, phenotypic and gene expression analyses, to unravel the regulatory hierarchy in acid resistance involving H-NS, RcsB-P/GadE complex, HdfR, CadC, AdiY regulators, and DNA-binding assays to separate direct effects from indirect ones. RcsB-P/GadE regulatory complex, the general direct regulator of glutamate-, arginine- and lysine-dependent acid resistance pathways plays a central role in the regulatory cascade. However, H-NS also directly controls specific regulators of these pathways (e.g. cadC) and genes involved in general stress resistance (hdeAB, hdeD, dps, adiY). Finally, we found that in addition to H-NS and RcsB, a third regulator, HdfR, inversely controls glutamate-dependent acid resistance pathway and motility.

Conclusions

H-NS lies near the top of the hierarchy orchestrating acid response centred on RcsB-P/GadE regulatory complex, the general direct regulator of glutamate-, arginine- and lysine-dependent acid resistance pathways.

SUBMITTER: Krin E

PROVIDER: S-EPMC2984483 | biostudies-literature | 2010 Oct

REPOSITORIES: biostudies-literature

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Publications

Decrypting the H-NS-dependent regulatory cascade of acid stress resistance in Escherichia coli.

Krin Evelyne E Danchin Antoine A Soutourina Olga O

BMC microbiology 20101029

<h4>Background</h4>H-NS regulates the acid stress resistance. The present study aimed to characterize the H-NS-dependent cascade governing the acid stress resistance pathways and to define the interplay between the different regulators.<h4>Results</h4>We combined mutational, phenotypic and gene expression analyses, to unravel the regulatory hierarchy in acid resistance involving H-NS, RcsB-P/GadE complex, HdfR, CadC, AdiY regulators, and DNA-binding assays to separate direct effects from indirec ...[more]

PMID: 21034467

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Project description:Enterohemorrhagic Escherichia coli (EHEC) is dependent on acid resistance for gastric passage and low oral infectious dose, and the locus of enterocyte effacement (LEE) for intestinal colonization. Mutation of rpoN, encoding sigma factor N (σ(N)), dramatically alters the growth-phase dependent regulation of both acid resistance and the LEE. This study reports on the determinants of σ(N)-directed acid resistance and LEE expression, and the underlying mechanism attributable to this phenotype. Glutamate-dependent acid resistance (GDAR) in TW14359ΔrpoN correlated with increased expression of the gadX-gadW regulatory circuit during exponential growth, whereas upregulation of arginine-dependent acid resistance (ADAR) genes adiA and adiC in TW14359ΔrpoN did not confer acid resistance by the ADAR mechanism. LEE regulatory (ler), structural (espA and cesT) and effector (tir) genes were downregulated in TW14359ΔrpoN, and mutation of rpoS encoding sigma factor 38 (σ(S)) in TW14359ΔrpoN restored acid resistance and LEE genes to WT levels. Stability, but not the absolute level, of σ(S) was increased in TW14359ΔrpoN; however, increased stability was not solely attributable to the GDAR and LEE expression phenotype. Complementation of TW14359ΔrpoN with a σ(N) allele that binds RNA polymerase (RNAP) but not DNA, did not restore WT levels of σ(S) stability, gadE, ler or GDAR, indicating a dependence on transcription from a σ(N) promoter(s) and not RNAP competition for the phenotype. Among a library of σ(N) enhancer binding protein mutants, only TW14359ΔntrC, inactivated for nitrogen regulatory protein NtrC, phenocopied TW14359ΔrpoN for σ(S) stability, GDAR and ler expression. The results of this study suggest that during exponential growth, NtrC-σ(N) regulate GDAR and LEE expression through downregulation of σ(S) at the post-translational level; likely by altering σ(S) stability or activity. The regulatory interplay between NtrC, other EBPs, and σ(N)-σ(S), represents a mechanism by which EHEC can coordinate GDAR, LEE expression and other cellular functions, with nitrogen availability and physiologic stimuli.

Project description:The transcription of the virulence plasmid (pINV)-carried invasion genes of Shigella flexneri and enteroinvasive Escherichia coli (EIEC) is induced at 37 degreesC and repressed at 30 degreesC. In this work, we report that the O135: K-:H- EIEC strain HN280 and S. flexneri SFZM53, M90T, and 454, of serotypes 4, 5, and 2a, respectively, produce apyrase (ATP-diphosphohydrolase), the product of the apy gene. In addition, the S. flexneri strains, but not the EIEC strain, produce a nonspecific phosphatase encoded by the phoN-Sf gene. Both apy and phoN-Sf are pINV-carried loci whose contribution to the pathogenicity of enteroinvasive microorganisms has been hypothesized but not yet established. We found that, like that of virulence genes, the expression of both the apy and the phoN-Sf genes was temperature regulated. Strain HN280/32 (a pINV-integrated avirulent derivative of HN280 which has a severe reduction of virB transcription) expressed the apy gene in a temperature-regulated fashion but to a much lower extent than wild-type HN280, while the introduction of the Deltahns deletion in HN280 and in HN280/32 induced the wild-type temperature-independent expression of apyrase. These results indicated that a reduction of virB transcription, which is known to occur in the pINV-integrated strain HN280/32, accounts for reduced apyrase expression and that the histone-like protein H-NS is involved in this regulatory network. Independent spontaneously generated mutants of HN280 and of SFZM53 which had lost the capacity to bind Congo red dye (Crb-) were isolated, and the molecular alterations of pINV were evaluated by PCR analysis. Alterations of pINV characterized by the absence of virF or virB and by the presence of the intact apy locus or intact apy and phoN-Sf loci were detected among Crb- mutants of HN280 and SFZM53, respectively. While all Crb- apy+ mutants of HN280 failed to produce apyrase, Crb- apy+ phoN-Sf+ mutants of SFZM53 lacked apyrase activity but produced a nonspecific phosphatase, like parental SFZM53. Moreover, the introduction of recombinant plasmids carrying cloned virF (pMYSH6504) or virB (pBN1) into Crb- mutants of HN280 and SFZM53 lacking virF or virB, respectively, fully restored temperature-dependent apyrase expression to levels resembling those of the parental strains. Taken together, our results demonstrate that, as has already been shown for invasion genes, apy is another locus whose expression is controlled by temperature, H-NS, and the VirF and VirB regulatory cascade. In contrast, the temperature-regulated expression of the nonspecific phosphatase does not appear to be under the control of the same regulatory network. These findings led us to speculate that apyrase may play a role in the pathogenicity of enteroinvasive bacteria.

Dataset Information

Decrypting the H-NS-dependent regulatory cascade of acid stress resistance in Escherichia coli.

Background

Results

Conclusions

Publications

Decrypting the H-NS-dependent regulatory cascade of acid stress resistance in Escherichia coli.

Similar Datasets

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