Incorporation of cholesterol into the cellular membrane of Lactobacillus acidophilus ATCC 43121.

Cholesterol that was assimilated by Lactobacillus acidophilus ATCC 43121 was not metabolically degraded; most of it was recovered with the cells. Cells that were grown in the presence of cholesterol micelles and bile salts were more resistant to lysis by sonication than were those grown in their absence, suggesting a possible alteration of the cell wall or membrane. Cholesterol assimilation occurred during growth at pH 6.0 as well as during growth without pH control. Part of the cholesterol that was assimilated by cells was recovered in the membrane fractions of cells grown under both conditions. There was no difference in the amount taken up from cholesterol micelles that were prepared using dioleoyl L-alpha-phosphatidylcholine or distearoyl L-alpha-phosphatidylcholine. Thus, the type of fatty acid (unsaturated or saturated) in the phospholipid did not influence the assimilation. As the amount of Tween 80 in the growth media increased beyond 0.05%, cholesterol uptake decreased, and the amount of growth remained the same. The higher concentrations of Tween 80 may have adversely affected the permeability of the cells.