title: CpxR/OmpR interplay regulates curli gene expression in response to osmolarity in Escherichia coli.
abstract: Curli fibers could be described as a virulence factor able to confer adherence properties to both abiotic and eukaryotic surfaces. The ability to adapt rapidly to changing environmental conditions through signal transduction pathways is crucial for the growth and pathogenicity of bacteria. OmpR was shown to activate csgD expression, resulting in curli production. The CpxR regulator was shown to negatively affect curli gene expression when binding to its recognition site that overlaps the csgD OmpR-binding site. This study was undertaken to clarify how the interplay between the two regulatory proteins, OmpR and CpxR, can affect the transcription of the curli gene in response to variation of the medium osmolarity. Band-shift assays with purified CpxR proteins indicate that CpxR binds to the csgD promoter region at multiple sites that are ideally positioned to explain the csg repression activity of CpxR. To understand the physiological meaning of this in vitro molecular phenomenon, we analyzed the effects of an osmolarity shift on the two-component pathway CpxA/CpxR. We establish here that the Cpx pathway is activated at both transcriptional and posttranscriptional levels in response to a high osmolarity medium and that CpxR represses csgD expression in high-salt-content medium, resulting in low curli production. However, csgD repression in response to high sucrose content is not mediated by CpxR but by the global regulatory protein H-NS. Therefore, multiple systems (EnvZ/OmpR, Cpx, Rcs, and H-NS) appear to be involved in sensing environmental osmolarity, leading to sophisticated regulation of the curli genes.
authors.affiliation: Unité de Microbiologie et Génétique Composante INSA, Villeurbanne, France.
authors.forename: Gregory
authors.initials: G
authors.lastname: Jubelin
authors.forename: Anne
authors.initials: A
authors.lastname: Vianney
authors.forename: Christophe
authors.initials: C
authors.lastname: Beloin
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Ghigo
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lazzaroni
authors.forename: Philippe
authors.initials: P
authors.lastname: Lejeune
authors.forename: Corinne
authors.initials: C
authors.lastname: Dorel
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000502:physiology; D012097:Repressor Proteins / Q000378:metabolism; D012462:Saline Solution, Hypertonic; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; C499694:CsgD protein, E coli; D029968:Escherichia coli Proteins; D012097:Repressor Proteins; D012462:Saline Solution, Hypertonic; D015534:Trans-Activators; C112177:osmolarity response regulator proteins; C077481:Crl protein, Bacteria; C085504:CpxR protein, Bacteria
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