Conservation of seven genes involved in the biosynthesis of the lipopolysaccharide O-side chain in Brucella spp.

Seven genes of the wb locus of Brucella melitensis 16M involved in the bios ynthesis of the lipopolysaccharide O-side chain have been recently identifi ed, i.e. wbkA, gmd, per, wzm, wzt, wbkB, and wbkC, coding, respectively, fo r proteins homologous to mannosyltransferase, GDP-mannose 4,6 dehydratase, perosamine synthetase, ABC-type transporter (integral membrane protein), AB C-type transporter (ATPase domain), a hypothetical protein of unknown funct ion, and a putative formyl transferase. The seven genes have a G + C conten t lower (around 48%) than that typical of Brucella spp. (58%) and thus may have been acquired from a species other than Brucella. In the present study , we analyzed by polymerase chain reaction-restriction fragment length poly morphism (PCR-RFLP) the seven O-chain biosynthetic genes for polymorphism a mong Brucella spp. PCR-RFLP showed that the seven genes are highly conserve d and occur even in the naturally rough species B. ovis and B. canis and al so in rough strains of B. abortus and B. melitensis. Nevertheless, the few polymorphisms that were observed consisted of absence of additional restric tion sites sometimes allowing differentiation at the species level (e.g. B, ovis) or at the biovar or strain level. There were no apparent deletions o r insertions in the PCR-amplified genes in any of the Brucella strains stud ied. In conclusion, the seven O-chain biosynthetic genes studied appear to be highly conserved among Brucella spp. and thus may have been acquired bef ore species differentiation. Some of the species- or biovar-specific marker s detected could be used for molecular typing of brucellae in addition to t hose previously described. (C) 2000 Editions scientifiques et medicales Els evier SAS.