Characterisation of the Burkholderia pseudomallei K96243 CPS I coding region.

: Burkholderia pseudomallei is 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. pseudomallei is essential for virulence. This B. pseudomallei capsular 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 genes within this region is unclear. We inactivated 18 of these genes and analysed 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 wcbN in B. pseudomallei K96243 retains the immunogenic integrity of the polysaccharide despite causing attenuation in the BALB/c murine infection model. Mice immunised with the B. pseudomallei K96243 mutants lacking a functional copy of either gmhA or wcbJ were afforded significant levels of protection against wild-type B. pseudomallei K96243 challenge.