Characterization of Putative RpoS-regulated Outermembrane Proteins Slp and OmpX in Escherichia coli 0157:H7

Abstract

E. coli 0157:H7 is a food pathogen with exceptional tolerance to certain stressful growth conditions. RpoS is a master regulator for bacterial stress adaptation and in particular, for acid resistance genes. The role of outermembrane proteins (Omps) in bacterial acid tolerance has not been investigated extensively. Omp profiles of strain EDL933(FRIK 47) and its isogenetic derivative IPOS mutant were compared. Omps downregulated in the rpoS mutant include Slp and OmpX. Putative RpoS-dependent promoter consensus sequences were identified in both slp and ompX. The expression levels of slp and ompX in the rpoS mutant were reduced compared to FRlK 47. Inactivation of slp reduced bacterial survival in pH3 at a similar level to the rpoS mutant. Our findings suggest that RpoS regulates production of two Omps, Slp and OmpX, and Slp is a key component of RpoS-dependent acid resistance system in E. coli OI57:H7.