Basal defined medium (BDM) containing vitamins, minerals and seven amino acids—(/L) tryptophan 0.1 g, methionine 0.2 g, valine 0.3 g, leucine 0.3 g, proline 0.3 g, leucine 0.4g and cysteine 0.5 g—which appeared to be essential for good growth of was prepared. Addition of glycine 0.2 g/L and threonine 0.4 g/L to BDM produced better growth of strain VPI 10463, and this defined medium was designated minimum amino acid-defined medium (MADM). Production of toxins A and B by strain VPI 10463 in 6 × MADM containing (/L) tryptophan 0.6 g, methionine 1.2 g, valine 1.8 g, leucine 1.8 g, proline 1.8 g, leucine 2.4 g, cysteine 0.5 g, glycine 0.2 g and threonine 0.4 g, was much greater than in MADM. Toxin production by 20 strains was examined in two defined media—6 × MADM and complete amino acid-defined medium (CADM) containing 18 amino acids—and one complex medium, modified brain heart infusion medium (m-BHI). Simultaneous production of toxins A and B by all test strains was demonstrated in m-BHI and the two defined media. It was also shown that 6 × MADM was generally better than CADM and as effective as m-BHI for stimulating toxin production by 13 strains. This defined medium would be useful for studies on the physiology, metabolism and pathogenicity of .


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