Abstract
Alanine, cystine, cysteine, β-hydroxypyruvate, an amino acid mixture and glycolaldehyde, which were found to satisfy the vitamin B6 (B6) requirement of Escherichia coli B WG3, a pdxB mutant, by paper disc assay method, were examined about the effect on growth of the mutant in liquid cultivation. Alanine and β-hydroxypyruvate did not significantly affected growth under the culture conditions, whereas cysteine and cystine supported growth to someextent. The amountof B6 synthesized by the mutant in the amino acid-supplemented mediumwas from 0.05 to 0. 12 nmol per ml. The amountof B6 synthesized in the medium, which was supplemented with an amino acid mixture composed of L-cysteine, L-threonine and L-methionine, was about 0. 15 nmol per ml. This amount of B6 was lower than the amount (0.4 nmol per ml) biosynthesized in glycolaldehydesupplemented medium. The data suggested that growth of the mutant supplemented with amino acids could not be supported by only the B6 biosynthesized from them, because such amounts of B6 were much smaller than the amount of B6 (0.6 nmol per ml) required for full growth of the mutant in minimal medium.
