[Sensitivity of Escherichia coli cell membranes to various classes of detergents]

The mechanisms of interaction between non-ionic or cationic surfactants with Escherichia coli K-12 cell membranes were studied using an approach based on the registration of changes in the membrane permeability to ethidium bromide, a fluorescent dye for nucleic acids. Triton X-100, a non-ionic detergent, was shown to exert no effect on the permeability of intact cell membranes. Triton X-100 interacted with the bacteria only after treatment with EDTA, a complexing agent for bivalent cations. Cetyltrimethyl ammonium bromide increased the permeability to ethidium bromide and the action of this cationic detergent did not require the pretreatment with the complexing agent. SDS, an anionic detergent, damaged E. coli K-12 and this could be registered by the lowering of intensity of light scattering by the bacterial suspension. The surface charge of E. coli K-12 cells was shown to influence the interaction of ionic detergents with bacterial cell membranes. Its variation by changing the pH of the incubation medium did not make E. coli K-12 sensitive to Triton X-100.