飲料用乳酸菌の研究-3-誘起突然変異株の栄養要求性および糖発酵性

概要

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Nutritionally deficient mutants were induced from Lactobacillus acidophilus strain Shirota, which was used for industrial production of lactic acid beverage. Since mutants were hardly obtainable by spontaneous mutation, penicillin-screening method combined with dialysis was applied to cells of late-exponential phase after irradiation with ultraviolet light. By these means, three auxotrophic mutants were obtained. Two strains (F 2 & F 3) were found to require L-lysine for growth, but assumed to have different mutant genes, since one of them (F 2) lost the ability to ferment lactose as an accompanied result of the lysineless mutation. Another mutant (F 1) required ribonucleotide, either 3' or 5'-phosphate ester of purine-or pyrimidine-ribonucleotide. None of deoxyribonucleotides, nucleosides, and some organic phosphate compounds were satisfactory for the requirement, except for p-nitrophenyl phosphate which exhibited similar effect as monoribonucleotides. The maximal growth of F 1 was proportinal to the amount of supplemented monoribonucleotide, as far as the concentration from 3μ mole to 20μ mole per ml of medium was concerned.
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