Global effect of RpoS on gene expression in pathogenic Escherichia coli O157:H7 strain EDL933

Abstract

BackgroundRpoS is a conserved stress regulator that plays a critical role in survival under stress conditions in Escherichia coli and other γ-proteobacteria. RpoS is also involved in virulence of many pathogens including Salmonella and Vibrio species. Though well characterized in non-pathogenic E. coli K12 strains, the effect of RpoS on transcriptome expression has not been examined in pathogenic isolates. E. coli O157:H7 is a serious human enteropathogen, possessing a genome 20% larger than that of E. coli K12, and many of the additional genes are required for virulence. The genomic difference may result in substantial changes in RpoS-regulated gene expression. To test this, we compared the transcriptional profile of wild type and rpoS mutants of the E. coli O157:H7 EDL933 type strain.ResultsThe rpoS mutation had a pronounced effect on gene expression in stationary phase, and more than 1,000 genes were differentially expressed (twofold, P < 0.05). By contrast, we found 11 genes expressed differently in exponential phase. Western blot analysis revealed that, as expected, RpoS level was low in exponential phase and substantially increased in stationary phase. The defect in rpoS resulted in impaired expression of genes responsible for stress response (e.g., gadA, katE and osmY), arginine degradation (astCADBE), putrescine degradation (puuABCD), fatty acid oxidation (fadBA and fadE), and virulence (ler, espI and cesF). For EDL933-specific genes on O-islands, we found 50 genes expressed higher in wild type EDL933 and 49 genes expressed higher in the rpoS mutants. The protein levels of Tir and EspA, two LEE-encoded virulence factors, were elevated in the rpoS mutants under LEE induction conditions.ConclusionOur results show that RpoS has a profound effect on global gene expression in the pathogenic strain O157:H7 EDL933, and the identified RpoS regulon, including many EDL933-specific genes, differs substantially from that of laboratory K12 strains.

Repression of Flagellar Genes in Exponential Phase by CsgD and CpxR, Two Crucial Modulators of Escherichia coli Biofilm Formation

“…Activation of csgD transcription by RpoS had been previously shown (27,50,51). As expected, the increase of cell motility is of comparable magnitude for the csgD and rpoS mutants, whereas the cpxR mutation has a much more drastic effect (Fig.…”

Hfq Virulence Regulation in Enterohemorrhagic Escherichia coli O157:H7 Strain 86-24

“…Differential regulation of the LEE among EHEC strains 86-24, EDL933, and Sakai has been observed in studies examining the roles of RpoS and GrlA in EHEC virulence (18,37,38,49,80,86). Moreover, Islam et al reported that the ler P1 promoter was the major promoter activating LEE expression in EHEC strains Sakai and EDL933 (37), whereas other studies have found that the ler P2 promoter was the major promoter in EHEC strain 86-24 (74, 78).…”

Solution Structure of the Guanine Nucleotide-binding STAS Domain of SLC26-related SulP Protein Rv1739c from Mycobacterium tuberculosis

“…Indeed, Rv1739c is among the sulfate transport and metabolism genes up-regulated in the dormant phase of infection in cultured macrophages and in granulomas of intact mice (58). Similarly, the STAS domain-containing SulP protein ychM of E. coli is also up-regulated in stress conditions of RpoN (54) deletion (59) and nitrofurantoin treatment (60), and severely down-regulated in a virulence-impaired E. coli O157:H7 strain with deletion of the conserved, alternative factor and stress regulator RpoS (61). The recent discoveries that E. coli ychM binds to acyl carrier protein, an abundant, small polypeptide with many additional interaction partners (62), and that its deletion influences multiple gene products that regulate fatty acid biosynthesis (18), add new complexity to these questions.…”