Alanine Dependence of Streptococcus faecalis R. ATCC8043 under Conditions of Vitamin B6 Deficiency.

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  • KARIYA Yasuhiro
    Department of Home Economics, Faculty of Education, Fukui University
  • OKADA Miyuki
    Department of Home Economics, Faculty of Education, Fukui University

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  • Ｓｔｒｅｐｔｏｃｏｃｃｕｓ　ｆａｅｃａｌｉｓ　Ｒ．　ＡＴＣＣ　８０４３のビタミンＢ６不含培地でのアラニンに対する依存性
  • Streptococcus faecalis R.ATCC8043 ノ ビタミ

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Abstract

Streptococcus faecalis R. ATCC 8043, a lactic acid bacterial strain used for the microbial assay of vitamin B6, is known to grow on alanine without addition of vitamin B6. It is evident that the strain requires vitamin B6 or one of the stereoisomers of alanine as an essential factor for growth. Cells grown on one alanine isomer in a medium deficient in vitamin B6 contain another type of stereoisomer of alanine as a constitutive element. The relative molecular ratio of the L-form of cellular alanine ranges from about 70% to 85%, even in cells grown on D-alanine as a growth factor. Cells grown on alanine produce vitamin B6-independent alanine racemase, indicating that the cells can racemize the stereoisomers in the absence of vitamin B6. Although alanine and vitamin B6 apparently stimulate the growth of Streptococcus faecalis R. ATCC 8043 in a similar manner, the mechanisms responsible for the growth stimulation by alanine and vitamin B6 are essentially different; vitamin B6 is used for the formation of the holo-enzyme of alanine transaminase, which is involved in the biosynthesis of alanine, whereas alanine acts as an essential growth factor.

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