Gram-Negative Bacteria Produce Membrane Vesicles Which Are Capable of Killing Other Bacteria

Naturally produced membrane vesicles (MVs), isolated from 15 strains of gram-negative bacteria (Citrobacter, Enterobacter, Escherichia, Klebsiella, Morganella, Proteus, Salmonella, and Shigella strains), lysed many gram-positive (including Mycobacterium) and gram-negative cultures. Peptidoglycan zymograms suggested that MVs contained peptidoglycan hydrolases, and electron microscopy revealed that the murein sacculi were digested, confirming a previous modus operandi (J. L. Kadurugamuwa and T. J. Beveridge, J. Bacteriol. 174:2767–2774, 1996). MV-sensitive bacteria possessed A1α, A4α, A1γ, A2α, and A4γ peptidoglycan chemotypes, whereas A3α, A3β, A3γ, A4β, B1α, and B1β chemotypes were not affected. Pseudomonas aeruginosa PAO1 vesicles possessed the most lytic activity.