Genetic variation at the omp2 porin locus of the brucellae: species-specific markers

The omp2 locus of Brucella abortus is composed of two closely related genes (omp2a and omp2b) that encode, and potentially both express, homologous porin proteins. Genetic variation at this locus is revealed in the form of restriction-fragment-length polymorphisms which can be used to distinguish the type strains of all six Brucella species. Five of the six species contain single copies of omp2a and omp2b, whereas Brucella ovis appears to have two copies of the omp2a gene. The implications of these results with regard to the physiological functions of the omp2a and the omp2b gene products, phylogeny of the genus, and species-specific adaptation are discussed.