The effect of oligolysines Lys-3, Lys-4, and Lys-5 on the outer membrane permeability of Pseudomonas aeruginosa.

A lysine polymer with five residues (Lys-5) was found to remarkably increase the outer membrane (OM) permeability of Pseudomonas aeruginosa to the tested hydrophobic probes (nitrocefin, N-phenyl naphthylamine, rifampin). Lys-3 and Lys-4 were inactive. The OM of Escherichia coli and Salmonella typhimurium was not permeabilized by Lys-5. Furthermore, even the action of Lys-5 on the Pseudomonas OM was abolished when the assays were performed in the presence of 150 mM NaCl instead of the low-ionic strength buffer earlier used by investigators studying the effect of polycations on the Pseudomonas OM.