Studies on the phospholipids and morphology of protoplasts of Bacillus megaterium

1. 1. The phospholipids of the membrane fraction of cells of Bacillus megaterium (MK 10D) cultured at pH 7.0 were found to consist of cardiolipin (5%), phosphatidyl ethanolamine (40%), phosphatidyl glycerol (40%) and O-lysyl phosphatidyl glycerol (15%). The content of phosphatidyl glycerol was decreased to 8% in cells harvested at pH 5.0, whereas glucosaminyl phosphatidyl glycerol represented 32% of the total phospholipids. The content of other phospholipids remained constant. 2. 2. Protoplasts derived from cells harvested from different media displayed a different behaviour during lysis experiments in hypotonic sucrose. 3. 3. Electron microscopy demonstrated that cells grown at pH 7.0 gave spherical protoplasts, whereas from cells exposed to pH 5.0, rod-shaped protoplasts were produced by lysozyme. In the latter protoplasts the original structure of the bacteria was maintained to a great extent even after exposure to hypotonic conditions. Similar protoplasts, when derived from cultures in which overnight the pH dropped from 7.0 to 5.0, also tend to preserve more of the original structural organisation. 4. 4. Environmental conditions may induce differences in chemical make-up or physical properties of lipoprotein structures resulting in significant variation in the morphology of bacterial protoplasts