Metabolism of Phospholipids in Bacillus stearothermophilus

Bacillus stearothermophilus B65 showed two stages of active logarithmic growth on a glucose based medium. Its incorporation of 32PO4 into phospholipids was higher at 55°C than at 37°C. At 37°C phosphatidylglycerol was the major phospholipid but at 55°C it was replaced by cardiolipin. Pulse-chase studies showed that turnover of phosphatidylglycerol and cardiolipin was extensive at certain stages of growth and indicated that phosphatidylglycerol could be the precursor of cardiolipin. Turnover rates at 37°C and at 55°C were similar. The proportion of phosphatidylethanolamine was highest when the pH of the medium was low. This phospholipid was stable at 37°C but at 55°C it might undergo a slow turnover.