Involvement of Intracellular Phospholipase C in Autolytic Fragmentation of Cytoplasmic Membranes of Bacillus cereus

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Abstract
Stoichiometry of changes in lipid composition during autolysis indicated that phospholipase C was involved in autolysis of the membranes of Bacillus cereus. Phosphatidylethanolamine and phosphatidylglycerol, which were main constituents of the membrane lipid, were hydrolysed by phospholipase C.The lipid‐rich material, which was released from the cell during autolysis, was found to be a kind of lipoprotein. Diglyceride, a product of phospholipase C, accounted for 69% of the total lipid in the released materials. Lipid/protein ratio of the material was calculated to be 1.56 (mg lipid/mg of protein). Electron microscopy of the material indicated that the material consisted mainly of membranous vesicles of about 0.2μm in diameter and had an “unit membrane” structure.From these results, it was concluded that the cytoplasmic membranes of B. cereus might be broken down at the site where phospholipid was hydrolysed by phospholipase C and the fragment was released into the medium.