Differential action of a streptococcal bacteriocin on mycoplasmas and microbial L-forms

Bacteriocin activity of Streptococcus faecalis var. zymogenes was tested against a variety of bacteria, L-forms, and mycoplasmas. Both a partially purified liquid preparation and a colony overlay technique were used. Other S. faecalis strains were the only bacteria whose growth was inhibited. The liquid preparation inhibited growth of all but three of the tested L-forms (whether derived from gram-positive or gram-negative bacteria), and two of these exceptional organisms were inhibited when the colony overlay technique was employed. On the other hand, the L-form of Streptobacillus moniliformis and all 33 tested mycoplasmas grew readily in the presence of the bacteriocin when either method was employed. It is suggested that the presence of cholesterol in the Streptobacillus and mycoplasmal membranes, unique in this regard among procaryotic cells, may be responsible for the differential pattern of growth inhibition.