The outer membrane of Brucella ovis shows increased permeability to hydrophobic probes and is more susceptible to cationic peptides than are the outer membranes of mutant rough Brucella abortus strains

The permeability of the outer membrane (OM) to hydrophobic probes and its s usceptibility to bactericidal cationic peptides were investigated for natur al rough Brucella ovis and for mutant rough Brucella abortus strains. The O M of B. ovis displayed an abrupt and faster kinetic profile than rough B. a bortus during the uptake of the hydrophobic probe N-phenyl-naphthylamine. B . ovis was more sensitive than rough B. abortus to the action of cationic p eptides. Bactenecins 5 and 7 induced morphological alterations on the OMs o f both rough Brucella strains. B. ovis lipopolysaccharide (LPS) captured co nsiderably more polymyxin B than LPSs from both rough and smooth B. abortus strains. Polymyxin B, poly-L-lysine, and poly-L-ornithine produced a thick coating on the surfaces of both strains, which was more evident in B. ovis than in rough B. abortus. The distinct functional properties of the OMs of these two rough strains correlate with some structural differences of thei r OMs and with their different biological behaviors in animals and culture cells.