Incorporation of cholesterol by membranes of bacterial L-phase variants with an appendix on the determination of the L-phase parentage by the electrophoretic patterns of cell proteins.

Abstract

SUMMARY L-phase variants of Streptobacillus moniliformis and Proteus mirabilis resembled mycoplasmas in their ability to incorporate considerable amounts of exogenous cholesterol into their cell membranes. Much smaller quantities were incorporated by L-phase variants of Streptococcus pyogenes and Staphylococcus aureus, by the parent bacteria of all L-phase variants except S. moniliformis, and by a series of wall-covered bacteria, including their protoplasts and spheroplasts. Cholesterol-binding ability corresponded roughly to sensitivity to growth inhibition and lysis by digitonin. Like myco-plasma, the S. moniliformis L-phase had a non-enzymic cholesterol uptake mechanism, but its growth in a cholesterol-free medium was not improved by adding cholesterol. It is concluded that a bacterium, on transforming to its stable L-phase, does not necessarily develop the ability to bind cholesterol; if it does, the cholesterol bound is not essential for growth of the L-phase, unlike cholesterol-requiring mycoplasmas.