ROLES OF CITRATE AND ACETOIN IN THE METABOLISM OF STREPTOCOCCUS DIACETILACTIS

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Abstract
Harvey , R. J. (University of California, Davis), and E. B. Collins . Roles of citrate and acetoin in the metabolism of Streptococcus diacetilactis . J. Bacteriol. 86: 1301–1307. 1963.— Streptococcus diacetilactis was unable to use citrate as a source of energy for growth, but the addition of citrate to a lactose-containing medium increased the specific growth rate 35%. Besides serving as the precursor of acetoin, some of the pyruvate formed from citrate was incorporated into cell material, primarily into lipids. A constant fraction of the weight of new cells was synthesized from the pyruvate formed from citrate. The rate of entry of citrate into cells was independent of the growth rate, and the usual result was that more pyruvate was formed from citrate than was required for cell synthesis. All excess pyruvate was converted to acetoin. Thus, acetoin formation acts as a detoxification mechanism, a means of removing intracellular pyruvate not required for synthesis of cell material.