Involvement of the Cpx signal transduction pathway of E. coli in biofilm formation

Abstract

In a genetic screening directed to identify genes involved in biofilm formation, mutations in the cpxA gene were found to reduce biofilm formation by affecting microbial adherence to solid surfaces. This effect was detected in Escherichia coli K12 as well as in E. coli strains isolated from patients with catheter-related bacteremia. We show that the negative effect of the cpxA mutation on biofilm formation results from a decreased transcription of the curlin encoding csgA gene. The effect of the cpxA mutation could not be observed in cpxR 3 mutants, suggesting that they affect the same regulatory pathway. The cpxA101 mutation abolishes cpxA phosphatase activity and results in the accumulation of phosphorylated CpxR. Features of the strain carrying the cpxA101 mutation are a reduced ability to form biofilm and low levels of csgA transcription. Our results indicate that the cpxA gene increases the levels of csgA transcription by dephosphorylation of CpxR, which acts as a negative regulator at csgA. Thus, we propose the existence of a new signal transduction pathway involved in the adherence process in addition to the EnvZ-OmpR two-component system. ß

Escherichia coli tol and rcs genes participate in the complex network affecting curli synthesis

“…This is an unexpected result, since until now the two operons have always been shown to be regulated in the same direction. Expression of these operons is positively regulated by OmpR (via the activation of CsgD) (Romling et al, 1998), and negatively regulated by CpxR (Dorel et al, 1999;Otto & Silhavy, 2002). We have investigated the possibility that the transcriptional regulation of the csg genes by tol-pal occurs through OmpR, CpxR and/or RcsB.…”

“…It involves H-NS (Arnqvist et al, 1992;Olsen et al, 1993), IHF (Gerstel et al, 2003), Crl (Arnqvist et al, 1994;Bougdour et al, 2004;Hammar et al, 1995) and MlrA (Brown et al, 2001). The OmpR/EnvZ (Prigent-Combaret et al, 2001;Romling et al, 1998) and CpxR/A (Dorel et al, 1999;Otto & Silhavy, 2002;Prigent-Combaret et al, 2001) phosphorelays also control curli expression. Using microarray analysis, the RcsC sensor kinase of the RcsB/CD phosphorelay has recently also been found to control csgD expression (Ferrieres & Clarke, 2003 The RcsB/CD His-Asp phosphorelay was initially identified as a positive regulator of the capsular exopolysaccharide biosynthesis gene cluster (wza-wca) in E. coli in association with RcsA (Gottesman & Stout, 1991;Stout, 1994).…”

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…Cpx is a two-component signaling pathway composed of the sensor kinase CpxA and the response regulator CpxR that responds to membrane stress (126). Consistent with its role in surface sensing, the Cpx pathway is activated upon surface interaction, and both the ⌬cpxR and ⌬cpxA mutants form less stable cell-surface interactions and biofilms with less biomass compared to those of the wild type when grown in microtiter plates (40,126). The transduction of the signals through this pathway is dependent on the outer membrane proteins OmpA and NlpE, with the latter likely being the direct sensor of contact with a surface, resulting in differential expression of genes involved in cellulose and P-pilus biosynthesis (96,126).…”

The diguanylate cyclase YddV controls production of the exopolysaccharide poly-N-acetylglucosamine (PNAG) through regulation of the PNAG biosynthetic pgaABCD operon

“…For Congo red (CR) and Calcofluor (CF) assays, overnight cultures were spotted, using a replicator, on agar media supplemented with 0.5 % Biofilm formation assays. Biofilm formation in microtitre plates was determined essentially as described by Dorel et al (1999). Bacterial cultures were grown overnight in M9Glu/sup at 30 uC in polystyrene microtitre plates (0.2 ml); the cell density of the culture was determined spectrophotometrically at 600 nm (OD 600 ).…”