Biology and Genetics of the Brucella Outer Membrane

International audience; The particular characteristics of the Brucella outer membrane (OM) are considered to importantly contribute to the biological properties of these bacteria that are able to survive in the hostile environment of phagocytes and cause persistent infections in diverse mammals. This contrasts with theBrucella's closest relatives in the genus Ochrobactrum which are only occasionally associated to opportunistic infections. High hydrophobicity, resistance to complement, bactericidal cationic peptides, detergents or EDTA, resistance to macrophage degradation or the protection against the host immune response are characteristics related to the Brucella OM. The O-polysaccharide chains of the smooth lipopolysaccharide (S-LPS) are a key component for the virulence of smooth strains but, since naturally rough B. canis and B. ovis that lack O-chains in the LPS are virulent in their respective natural hosts, other traits must have a significant role in virulence. Heterogeneity in LPS, OM proteins, and phospholipids draw a particular OM for each Brucellaa species (in some instances at the biovar or strain level) with a definite composition and topology. This variability leads to modifications in the antigenic and functional properties that could affect the interaction with the host and be related to the differences in pathogenicity and host tropism among the Brucellae.