The nutrition of Staphylococcus aureus ; nicotinic acid and vitamin B1

Abstract

HITHERTO Staphylococcus aureus has not been grown in media of completely known chemical composition. With a medium in which most of the nutrients were known (amino-acids and glucose) it has been necessary to add a supplement, quantitatively very small but qualitatively essential, before growth can occur. The necessity for the supplement was first shown by Hughes [1932] and later by Knight [1935], who used autolysed yeast extract (marmite) as a rich source of the growth factor and acid-hydrolysed gelatin plus glucose as the deficient basal medium. Subsequently it was found possible [Fildes et al. 1936] to substitute a collection of amino-acids plus glucose for the gelatin hydrolysate basal medium. The present paper shows that the active concentrate from yeast obtained by Knight, which must be given to S. aureus for growth to take place, can be replaced by nicotinic acid and vitamin B1 together, neither alone being effective. It is therefore now possible to grow a typical strain of S. aureus on a medium containing only known chemical components. Technique of the biological testing For much of the work on the staphylococcus growth factor the basal deficient medium used was the gelatin hydrolysate medium already described [Knight, 1935]. The growth factor under investigation was, by definition, that supplement which would permit S. aureus to grow aerobically on this basal medium. It was always borne in mind that the growth factor might be in fact a complex, as indeed proved to be the case, and further, that the gelatin itself might be contributing an essential nutrient component besides its content of amino-acids. In the sequel it is shown that this was so. Subsequently, when the amino-acid basal medium had been developed [Fildes et al. 1936] samples of growth factor were tested on both the gelatin and the amino-acid basal media, and it was found that certain fractions were active on the gelatin but inactive on the amino-acid basal medium. The standard preparation of growth factor, the high-vacuum distillate (see later), was active on both basal media. Technical details of the preparation and inoculation of the media are given in the above papers, the aim being to achieve maximum purity of materials, and to use as small an inoculum as possible to minimize " carry-over " of active material from the parent cultures. Estimation of biological activity of preparations. The routine method adopted for determining the distribution of active material between various fractions in the chemical separation was to compare their activities at a dilution equivalent to 1 % solutions of the amount of marmite from which the fractions were originally derived, by titration in serial dilutions in the basal deficient medium. Halley Stewart Research Fellow. (731)