Morphological mutants of Escherichia coli: nature of the permeability barrier in mon and envC cells.

Morphological mon mutants and a chain-forming envC mutant of Escherichia coli K12 are hypersensitive to detergents and to various other antibacterial agents. Electron microscopy shows that the cytoplasmic membrane of growing mon and envC cells is dissolved by detergents, and that the cytoplasm dissociates into two parts of unequal density. The mutant envC is sensitive to actinomycin D and to rifampicin, is lysed by lysozyme in the absence of EDTA, and releases alkaline phosphatase in the absence of osomotic shock, indicating a gross perturbation of its outer membrane.