ORGANIC-ACID EXCRETION BY STREPTOMYCES-LIVIDANS TK24 DURING GROWTH ONDEFINED CARBON AND NITROGEN-SOURCES

Cultures of Streptomyces lividans TK24 grown in defined media containi ng certain rapidly used carbon and nitrogen sources excreted high leve ls of organic acids. These were identified by HPLC and enzymic assays as pyruvic acid and 2-oxoglutaric acid. Acidification occurred only wi th glucose as the principal carbon source, and depended on the nitroge n source used. With nitrate as the sole nitrogen source. high levels o f pyruvate and small amounts of 2-oxoglutarate were produced. Carbon f rom D-[U-C-14]glucose was converted Biochemistry and into both organic acids. Combining glucose with a selection of amino acids as Molecular Biology, primary nitrogen/secondary carbon sources yielded less pyruv ate and more 2-oxoglutarate. Carbon from both C-14-labelled glucose an d amino acids was metabolized to both organic acids. Adding nitrate to this combination caused a reversion of the acid production pattern to that of the glucose-nitrate combination. as if the amino acids were a bsent. Addition of ammonium salts to any combination of carbon and nit rogen sources completely prevented organic acid formation.