Mode of action of polymyxin B: physiological studies with Bacillus subtilis-resistant mutant.

Polymyxin B resistance in Bacillus subtilis can be suppressed by the synergistic action of lysozyme or of an analogous cell wall lytic activity released by B. subtilis spores during germination. Such a synergistic effect is probably due to partial cell-wall digestion by lysozyme that allows polymyxin to reach its site of action and is therefore distinct from the analogous synergistic effect described by other authors in Escherichia coli. In the latter case polymyxin B probably damaged the outer membrane, allowing lysozyme to reach and digest the cell wall.