Fractions of Trypsinized Casein giving Different Patterns of Bacterial Growth

Abstract

THE rate of growth of a strain of Streptococcus equisimilis in a medium comprising acid-hydrolysed casein, glucose and yeast extract has been shown in these Laboratories to be markedly increased by the addition of a small amount of a tryptic digest of casein. While investigating this effect, which had been shown not to be due to the ability of the enzymic digest to supply free amino-acids, it was found to be possible by chromatography on paper in n-butanol/acetic acid/water (25 : 6 : 25 by vol.) to fractionate the digest in such a way as to separate compounds possessing growth-stimulating activity of two distinct types. Thus constituents of the digest possessing approximately the same R _F as that of glycine resulted, after a very short lag, in a sudden increase in the rate of growth of the organisms which, however, was of short duration (Fig. 1a). On the other hand, the effect of constituents of the digest with R _F values similar to that of valine reached a maximum only after a prolonged lag and differed again from the previous effect in that the high rate of growth was sustained (Fig. 1b).