DESOXYRIBOSIDES AND VITAMIN B 12 AS GROWTH FACTORS FOR LACTIC ACID BACTERIA

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Abstract
18 strains of lactic acid bacteria, representative of 6 spp. and hitherto not cultured in media of known composition, were examined for certain additional nutritional requirements. None of these bacteria grew in a medium complete with respect to known amino acids and synthetic vitamins and supplemented with tomato juice and an enzymatic digest of casein. All grew when thymidine was added to this medium. In most cases, thymidine could be replaced by either hypoxanthine desoxyriboside, adenine desoxyriboside, guanine desoxyriboside, cytosine desoxyriboside, or high levels of desoxyribonucleic acid. Individual differences in the avialability of the various desoxyribosides were noted. Several organisms (e.g., Lactobacillus delbrueckii 730) grew more rapidly and heavily with thymidine than with other desoxyribosides, and one, Leuconostoc citrovorum 8081, grew only with thymidine. For a few other organisms, cytosine desoxyriboside appeared to be more active than other desoxyribosides. Most organisms showed delayed growth with desoxyribonucleic acid. Vitamin B12 replaced thymidine (or other desoxyribosides) for many, but not all, of these organisms. L. delbrueckii 730 and Lactobacillus acidophilus 204 are examples of organisms that respond to thymidine, but not to vitamin B12. Ascorbic acid, thioglycolic acid, cysteine, or glutathione replaced thymidine, other desoxyribosides, or vitamin B12 for many of these organisms in media that contained an enzymatic digest of casein. For most organisms, these reducing agents were ineffective in eliminating the requirement for these growth factors when the enzymatic casein digest was omitted from the medium. L. acidophilus 204, L. acidophilus S, and Lactobacillus helveticus S, however, grew well when ascorbic acid was supplied under these latter conditions. When added aseptically to previously autoclaved media, vitamin B12 and vitamin Bl2b were equally active in promoting growth. Sterilization with the medium reduced the activity of vitamin Bl2b to approx. 1/7 that of vitamin Bl2. Although all organisms required similar amts. of the active desoxyribosides for growth, a very considerable variation in the amts. of vitamin Bl2 required was observed.