INTRACELLULAR EVENTS OCCURRING DURING ENDOTROPHIC SPORULATION IN BACILLUS MYCOIDES

Abstract

The intracellular content, in B. mycoides, of certain free amino acids, purines, and pyrimidines is reduced appreciably as cells undergo endotrophic sporulation. Antimetabolites which inhibit sporulation inhibit disappearance of the above substances. Irrespective of their known specificity, the antimetabolites inhibit utilization of all the above substances. This all-or-nothing inhibition behavior is interpreted as meaning that during endotrophic sporulation, nucleoprotein is synthesized from the low molecular wt. substances, for which synthesis all the building blocks are required simultaneously. Using fixation of S35-methionine into insoluble material as a criterion of protein synthesis, a significant peak in synthesis occurred between the 5th and 8th hrs. of the endotrophic sporulation process, which was displayed well before onset of visible sporulation. Known inhibitors of endotrophic sporulation, norleucine, 2,6-diaminopurine, and a pH of 5.0, each inhibit the pre-spore protein synthesis as shown by fixation of S35.methionine. Glucose, which inhibits sporogenesis, increases S35-methionine uptake. These results are in accord with our concept of the nature of sporogenesis. Using solubilization of fixed S35-methionine from S35 labeled cells as criterion of protein degradation, a definite peak of protein synthesis was shown to occur. The above results provide exptl. support for the hypothesis that endotrophic sporulation involves a de novo synthesis of at least some of the spore matter and that this synthesis utilizes intracellular low molecular wt. compounds which are generated as needed by degradation of preexisting components characteristic of the vegetative cell.