EFFECT OF LIPID-COMPOSITION OF MYCOPLASMA-MYCOIDES SUBSPECIES CAPRI AND PHOSPHATIDYLCHOLINE VESICLES UPON ACTION OF POLYENE ANTIBIOTICS

The effects of filipin and amphotericin methyl ester upon the K+ efflux from M. mycoides ssp. capri and egg lecithin sonicated vesicles were investigated. The nature of the sterol and the composition of the membranes affected the sensitivity to each polyene antibiotic. M. mycoides ssp. capri containing ergosterol was much more sensitive to amphotericin methyl ester than cells containing cholesterol. Cholesterol-containing cells were about twice as sensitive to filipin as the ergosterol-containing cells. These results were confirmed with phosphatidylcholine vesicles. At 2.degree. C the filipin sensitivity of M. mycoides ssp. capri was independent of the membrane cholesterol content and the sensitivity towards amphotericin methyl ester decreased when the membrane cholesterol content was increased, in contrast to the results at 20.degree. C. At 2.degree. C, sterol-free egg lecithin vesicles became very sensitive to filipin and amphotericin methyl ester and the presence of cholesterol in the vesicles did not increase the sensitivity further. At high concentrations of cholesterol (> 30 mol%), the polyene antibiotic sensitivity, particularly, towards amphotericin methyl ester, was greatly reduced.