Differences in cellular fatty acids and lipid composition inClostridium pasteurianum under nitrogen-and non-nitrogen-fixing conditions

Clostridium pasteurianum total cellular saturated fatty acids increased through its growth cycle from 81% to 91% but varied significantly in the composition under nitrogen- and non-nitrogen-fixing conditions. During ammonia-assimilating growth, palmitic acid decreased from 67.7% to 43.5% by late log while marked increases in shorter chain saturated fatty acids (C_15:0 and below) and a long chain saturated C_22:0 occured. In contrast, under N₂-fixing growth conditions, palmitic acid increased from 45.5% to 84.3% by late log, representing nearly the total amound of saturated fatty acids found inC. pasteurianum. The total cellular lipid concentration decreased as the culture aged. irrespective of the nitrogen sources; however, the phospholipid concentration increased significantly during N₂-fixing growth as compared with a 50% decrease during ammonia-assimilating conditions. The implication of these differences and possible role of palmitic acid and phospholipids inC. pasteurianum nitrogen fixation process are discussed.