ENDOGENOUS FACTOR IN SPOROGENESIS IN BACTERIA. II. GROWTH AND SPORULATION IN BACILLUS SUBTILIS.

Kerravala, Zarrine J. (University of Illinois, Urbana), V. R. Srinivasan, and H. Orin Halvorson. Endogenous factor in sporogenesis in bacteria. II. Growth and sporulation of Bacillus subtilis. J. Bacteriol. 88:374-380. 1964.-The presence of an endogenous factor in Bacillus subtilis which could initiate sporogenesis in suspensions of washed vegetative cells was demonstrated. The inability to obtain a culture of vegetative cells, relatively free from spores, by the "active culture" technique necessitated the use of the "continuous culture" method. The investigations on the continuous cultivation of this organism, to obtain a steady-state population of actively growing vegetative cells, resulted in certain observations which gave an insight into the nature of sporogenesis. Growth studies of the organism under these conditions showed that there was a rise in viable cell numbers, until a maximal population was reached. This was maintained at a steady-state level for sometime; on further incubation, there was a reduction in cell numbers, and consequently the steady state could not be maintained any longer. Spore counts showed that the spore fraction of the total population increased on prolonged incubation. The commitment to sporulation appeared to have caused a reduction in the growth rate of the population, which was experimentally demonstrated by a decline in cell numbers. In contrast, when B. cereus strain T. was grown as a continuous culture, it could be maintained as a steady-state population of vegetative cells, for longer periods, like a nonsporeformer (e.g., Escherichia coli). This difference in behavior could be attributed to the fact that whereas B. subtilis can sporulate in the presence of nutrients, B. cereus strain T. cannot do so until the medium has been depleted of nutrients.