Outer Membrane Proteins of Pseudomonas aeruginosa: Their Role in Antibiotic Susceptibility.

The outer membrane OM of Pseudomonas aeruginosa, when grown in a glucose-basal salts medium, contained five major OM proteins with molecular weights, in daltons, of 50,000, 48,000, 42,000, 18,000 and 17,000 plus a 9,000-dalton protein which may be a Braun lipoprotein-like component. An additional major 22,000-dalton OM protein was detected when cells were grown in a complex medium. Experimental evidence suggested that the 18,000-dalton protein was associated with the peptidoglycan fraction. Cells of P. aeruginosa containing an RP1 plasmid which codes for resistance to several antimicrobial agents including tetracycline resistance, were studied. The R cells contained an additional 35,000-dalton OM protein. The R cells were also unable to take uptransport tetracycline but, incubation with EDTA caused a transient uptake of tetracycline. Studies were carried out on the uptaketransport of gentamicin by P. aeruginosa. The revealed that the first step in the uptake of gentamicin was the firm binding of gentamicin to the cell envelope.