Acetate stimulation of Lactobacillus delbrueckii and its replacement of nucleosides.

Studies of the acetate stimulation of lactobacilli have led to the discovery of two acetatereplacing factors now known as lipoic and mevalonic acids (Guirard et al., 1946; Skeggs et al., 1956). These two acetate-replacing factors have been shown to be active for many microorganisms. However, there still remain some lactic acid bacteria which require acetate for early growth and for which lipoic and mevalonic acids are inactive. Lactobacillus delbrueckii is one organism whose acetate stimulation is not duplicated by lipoic acid (Peters and Snell, 1954) or, as is reported here, by mevalonic acid. Little work has been done on the acetate enhancement of L. delbrueckii, no doubt, because of the difficulty in obtaining minimal growth, or lack of growth in the "blanks" or tubes without added acetate. When there is much growth in the blanks, the working range of the acetate doseresponse curve is reduced and thus makes difficult a quantitative study of its stimulation. Occasionally, growth will not appear in acetate-free tubes; however, the addition of minimal amounts of acetate gives complete growth. In an effort to reduce the growth of L. delbrueckii in tubes devoid of acetate, a rather extensive studv of the media usually used with this organism was undertaken. Some of the results, presented here, show that there appears to be still another way in which acetate enhances early growth of lactobacilli which does not involve the production or immediate activity of either lipoic or mevalonic acids. It was also found that any of several nucleosides or nucleotides may be considered as behaving as acetate replacing factors.