Abstract
Nonpolar and polar lipids of an alkalophilic bacterium, Bacillus sp. A-007, were analyzed by use of column, thin-layer, paper and gas-liquid chromatography and gas chromatography-mass spectrometry. The major nonpolar lipids were diacylglycerols (56% of nonpolar lipids), squalene and dehydrosqualene (24%). Polar lipids were composed of seven species of phospholipids. Phosphatidylglycerol (PG, 67% of polar lipids), phosphatidylethanolamine (PE, 21%), cardiolipin (CL, 7%) and bis (monoacylglycero) phosphate (BMP, 4%) were predominant phospholipids and these accounted for 99% of the total polar lipids. One minor phospholipid was phosphatidic acid and the other two were not identified because of their very low contents. The ratio of nonpolar lipids to polar lipids was 4:6. It is notable that glycolipids and phosphoglycolipids, which are commonly distributed in many kinds of Gram-positive bacteria, were completely absent in strain A-007 and all of the other three strains of alkalophilic bacilli examined. Fatty acids of total lipid were mainly composed of iso C15:0, anteiso C15:0, n C16:0 and iso C17:0 acids which were similar to those of Bacillus subtilis W23. No significant difference in fatty acid composition was seen among major lipids. Positional distribution of fatty acids of PG and PE were determined based on the specificity of phospholipase A2 hydrolysis of the lipids. In both phospholipids, longer chain fatty acids were concentrated at C-1 position of the glycerol moiety and the shorter ones at C-2 position. The other three alkalophilic strains of Bacillus species contained similar lipids but one of them (Bacillus sp. A-40-2) lacked BMP. In vivo experiments of phospholipid metabolism showed that PG was a precursor of BMP and CL, and the turnover of PG was slow in Bacillus sp. A-007 in comparison with that in B. subtilis W23.
