Characterization of the Burkholderia pseudomalleiK96243 Capsular Polysaccharide I Coding Region

Burkholderia pseudomalleiis the causative agent of melioidosis, a disease endemic to regions of Southeast Asia and Northern Australia. Both humans and a range of other animal species are susceptible to melioidosis, and the production of a group 3 polysaccharide capsule in B. pseudomalleiis essential for virulence. B. pseudomalleicapsular polysaccharide (CPS) I comprises unbranched manno-heptopyranose residues and is encoded by a 34.5-kb locus on chromosome 1. Despite the importance of this locus, the role of all of the genes within this region is unclear. We inactivated 18 of these genes and analyzed their phenotype using Western blotting and immunofluorescence staining. Furthermore, by combining this approach with bioinformatic analysis, we were able to develop a model for CPS I biosynthesis and export. We report that inactivating gmhA, wcbJ, and wcbNin B. pseudomalleiK96243 retains the immunogenic integrity of the polysaccharide despite causing attenuation in the BALB/c murine infection model. Mice immunized with the B. pseudomalleiK96243 mutants lacking a functional copy of either gmhAor wcbJwere afforded significant levels of protection against a wild-type B. pseudomalleiK96243 challenge.