Incorporation of cholesterol into the cellular membrane of Bifidobacterium longum

Four strains of Bifidobacterium longum were isolated from feces of human intestinal sources and were tested along with four commercially available strains of B. longum for bile tolerance, the ability to deconjugate sodium taurocholate, and the ability to remove cholesterol from the culture medium. The cultures varied with respect to each test. There was no relationship between bile tolerance and the ability to remove cholesterol. Relative deconjugation of sodium taurocholate also was not related directly to the amount of cholesterol that was removed by the cultures. However, inclusion of sodium taurocholate in the growth medium enhanced the ability of B. longum to remove cholesterol from the medium during growth. A portion of the cholesterol that was removed from the growth medium by B. longum was recovered in the cellular membrane fraction, suggesting some assimilation of cholesterol into the membrane. Cells that were grown in the presence of cholesterol and taurocholate were more resistant to sonication than were those grown in the control broth or in the broth containing the bile salt without cholesterol, which is evidence that the cell envelope was affected by the cholesterol.