Protein metabolism during germination of Bacillus megaterium spores. I. Protein synthesis and amino acid metabolism.

Protein synthesis during germination of Bacillus megayerium spores can be divided into two stages. During the first 75 min of germination (Stage I) endogenous nitrogen reserves are sufficient to support protein synthesis, and most amino acids are generated by proteolysis of dormant spore protein. The amino acids produced are excreted initially from the spore, but then reabsorbed and partially utilized for protein synthesis. Significant amino acid metabolism also occurs during Stage I, utilizing enzymes already present in the dormant spore. The biosynthesis of a number of amino acids is low or absent during Stage I due to the absence of biosynthetic enzymes. Subsequently, at defined times in Stage I, these missing enzymes are synthesized and amino acid biosynthesis is initiated. By the beginning of Stage II (from 75 min on) the developing spore has regained the capacity for synthesis of all amino acids and requires an exogenous nitrogen source for rapid protein synthesis.