The Periplasmic Chaperone SurA Affects Motility and Biofilm Formation via the RcsCDB Pathway in Salmonella enterica Serovar Typhi.

SurA, a periplasmic chaperone, is a key factor in the biogenesis of β-barrel outer membrane proteins (OMPs). It is also associated with virulence, invasion and biofilm formation in Escherichia and Salmonella species. To investigate whether SurA affects bacterial motility and biofilm formation in Salmonella enterica serovar Typhi, we prepared a surA deleted mutant. Motility assay and quantitative real-time PCR (qRT-PCR) indicated that surA deletion reduced swimming motility and decreased flagellar gene expression, respectively. β-galactosidase assay and qRT-PCR further showed that surA deletion also activated the RcsCDB pathway, which we verified affected motility. We also examined the effects of the surA deletion on biofilm formation and established that the surA mutant exhibited significantly reduced ability to form biofilms compared with the wild-type. From our findings, we proposed that the periplasmic chaperone, SurA, affects flagella expression via the RcsCDB pathway thereby influencing biofilm formation in Salmonella enterica serovar Typhi. Collectively, these studies confirmed a new physiological role for SurA in Salmonella enterica serovar Typhi.