Biochemical changes in Bifidobacterium bifidum var. pennsylvanicus after cell wall inhibition. VIII. Composition and metabolism of phospholipids at different stages and conditions of growth.

1. The phospholipid content and composition of Bifidobacterium bifidum var. pennsylvanicus is markedly influenced by the growth phase, the pH and the presence of human milk in the culture medium. 2. The lipid-phosphorus content of the cells increases during the first period of active growth, but decreases later. The lipid-phosphorus content of the cells in the stationary phase is at constant pH 5.5 about 45 percent of that at constant pH 6.8 and final pH 5.2. This difference is caused by a general reduction of all types of phospholipids. 3. Phosphatidylglycerol content decreases during growth, diphosphatidylglycerol increases in the first period, but decreases later and especially in the stationary phase by an increase of its lysoderivatives. The phosphogalactolipids rise during growth in the non-controlled pH-culture to 70 percent of the phospholipids in the stationary phase. When pH is constant at 6.8 and 5.5 glycerolphosphorylgalactosyldiglyceride remains at a constant level of about 20 percent during growth. At pH 6.8 glycerophosphorylmonogalactosylmonoglyceride increases to 24 percent during cultivation; at pH 5.5 this lipid contributes only a few percent. 4. Under all pH conditions, lack of human milk in the culture medium causes a marked increase of the lipid-phosphorus content of the cell, together with a high increase of the relative amounts of diphosphatidylglycerol and phosphatidylglycerol and a decline of the phosphogalactolipids. The same changes are observed after inhibition of cell wall synthesis by various antibiotics, but not after inhibition of protein synthesis.