Isolation and characterization of two distinct fractions from the inner membrane of dormant Bacillus megaterium spores.

Two distinct membrane bands were obtained after sucrose velocity gradient centrifugation of crude inner membranes from dormant Bacillus megaterium spores disrupted under conditions which minimized endogenous enzyme action. These two inner membrane fractions (termed LD and HD) contained similar amounts of total and individual phospholipid species. However, LD and HD differed significantly in phospholipid/protein ratios (4.3 and 0.47 mg/mg, respectively), equilibrium densities (1.12 and 1.18 g/cm3), NADH oxidase specific activity (less than 0.01 and 0.13 mumol/min X mg), and content of specific proteins. In contrast, crude membranes prepared in identical fashion from germinated spores gave only a single inner membrane band (termed G) on sucrose velocity gradients. G had a phospholipid/protein ratio of 0.98 mg/mg, an equilibrium density of 1.16 g/cm3, and an NADH oxidase specific activity of 2.1 mumol/min X mg. Essentially all of the proteins present in LD or HD or both were found in G, consistent with the latter membrane being derived from a mixture of LD and HD. No evidence was found suggesting that there is significant degradation of dormant spore inner membrane protein upon spore germination.