Stabilizing effect of colicin E2 on the "spheroplast membrane".

Cells of Escherichia coli W3110 and its thymineless mutant, both of which are colicin E2 sensitive, were treated with colicin E2, and then converted to spheroplasts. These spheroplasts seemed to be more stable than those from untreated cells; suspensions of spheroplasts of untreated cells were lysed spontaneously and the turbidity was reduced by approximately 45% on incubation with ethylenediaminetetraacetic acid-lysozyme, whereas suspensions of spheroplasts of colicin E2-treated cells showed 25% reduction in turbidity. This change was irreversible and 5 min of treatment with colicin E2 at 37 C was necessary for stabilization. This process was inhibited by 2,4-dinitrophenol or streptomycin. Cells harboring the colicin E2 factor were not affected by treatment in this way with colicin E2. Alteration of composition of phospholipids was not observed.