Cytological and Chemical Studies of the Growth of Protoplasts of Bacillus megaterium

Abstract

Aeration of protoplasts of Bacillus megaterium in a succinate buffered nutrient broth led to marked growth similar to that already described by McQuillen, and the degree of chromatin synthesis in these growing forms prompted a combined cytological and chemical study. Growth was followed by phase contrast and by Feulgen stains, as well as by lipide phosphorus, nucleic acid, and protein analyses. In slide cultures, growth and compression led to monstrous flattened forms with readily visible, but coalescent nuclear structures. In fluid cultures, the protoplasts grew as phase dense spheres. Orderly reproduction of apparently discrete nuclear bodies was observed during the initial hours of spherical growth, but in older cultures, the chromatin arrangement tended to be more haphazard and was influenced by the concentration of Mg ions. In the same medium, protoplasts free of lysis showed a linear rise in optical density, while vegetative cells exhibited an exponential increase. However, protoplasts were able to synthesize DNA at the same rate as vegetative cells, but their increase of RNA was always less. Thus, as they grew, the ratio RNA/DNA fell. The lipide P increased in proportion to the expanding surface. With growth and lysis, large amounts of water-insoluble slime accumulated. Analyses indicate it to be a phospholipoprotein material containing some RNA.