Role of the capsule locus in the virulence of Bordetella pertussis

Abstract

Bordetella pertussis, produces a surface microcapsule but its role in pertussis pathogenesis remained to be investigated. B. pertussis mutants deleted for the polysaccharide capsule biosynthesis, transport and export genes within the capsule locus showed that the capsular transporters at the inner membrane in particular KpsT, is essential for in vivo virulence. The phenotype observed in a kpsT-deleted mutant corresponds to the down-regulation of key virulence factors at both transcriptional and protein levels. We revealed a novel functional link between KpsT and BvgA/S, the master two-component system, which regulates most of B. pertussis virulence genes expression. Oligomerization of BvgS and the sensor?s activity are impaired in kpsT-deleted mutant, implying an alternative biological function of the capsular transporter KpsT in the central functioning of BvgS-mediated signal transduction in B. pertussis. In addition, we observed that the capsule locus is highly expressed and dynamically modulated during cellular adherence and invasion, as well as during the course of in vivo infection, reflecting the response of the bacteria to the host microenvironments during infection.