SUMMARY: grown in media containing amino acids and glucose or other carbohydrates (including glycerol), secreted pyruvate, acetate, acetoin, butanediol, and small quantities of isobutyrate and isovalerate. The enzymes producing acetoin and butanediol were specifically induced by acetate and weakly by propionate. Even when these enzymes were present, acetate accelerated the rate of acetoin production. Since acetoin and butanediol are readily interconverted (via butanediol dehydrogenase), they serve as an oxidation-reduction buffer for NAD/NADH. When carbohydrate was exhausted, acetate and, more slowly, acetoin were oxidized.

Mutants unable to produce acetoin or acetate were blocked in the metabolic path from the carbohydrate to these compounds. Other mutants unable to re-utilize the compounds were either deficient in the necessary enzymes, e.g. of citric acid cycle, or they stopped growth so early that they could not use up the carbohydrate. In particular, a uracil-requiring mutant stopped growth precociously, did not oxidize acids or acetoin, and was unable to sporulate. Addition of uracil restored all these properties to normal. The differences in secretion and re-utilization of metabolites can be employed to classify unidentified sporulation mutants.


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