CHEMICALLY DEFINED MEDIUM FOR GROWTH STREPTOCOCCUS PYOGENES.

Mickelson, M. N. (National Animal Disease Laboratory, Ames, Iowa). Chemically defined medium for growth of Streptococcus pyogenes. J. Bacteriol. 88:158-164. 1964.-Three strains of group A hemolytic streptococci representing three serological types were serially subcultured for an extended period (100 or more transfers) in a peptide-free and protein-free culture medium. An amino acid assay medium, modified by addition of small amounts of glutamine, ammonium acetate, and 0.1 m phosphate (pH 7), was used. In this medium, high concentrations of glutamic acid or glutamine were required, and biotin was stimulatory to growth. Biotin could be partially replaced with NaHCO(3). Maximal growth was obtained with NaHCO(3) when biotin was present, and aspartic acid and asparagine were omitted from the medium. In 24 to 48 hr of incubation at 37 C, luxuriant growth was obtained with complete removal and quantitative fermentation of 1% glucose to lactic acid. Optical densities of cultures were equivalent to those obtained with the best infusion media.