Studies on Cultural Requirements of Bacteria

Abstract

The nutritive requirements of a strain of diphtheria bacillus were studied with particular reference to substances supplied by tissue extractives. Known amino acids previously shown to be utilized by this strain were supplied in control media. A by-product fraction of commercial liver extract was fixed upon as suitable crude material. This consisted of the filtrate obtained after removing the precipitate resulting from the addition of absolute ethyl alcohol up to a strength of 95% to a concentrated aqueous liver extract. The alcohol was removed from this filtrate by vacuum distillation, the resulting solution was then precipitated by lead acetate, the precipitate discarded, and the Pb removed from the filtrate with H2S. It was then adsorbed twice with norit charcoal, and the latter eluted with acid alcohol. To obtain maximal growth it was necessary to add both the elute and the charcoal filtrate to the control solution. The effect of the charcoal filtrate was shown to be due to its content of inorganic material, particularly K and Mg, which were deficient in the salt mixture at first used.[long dash]VII. A strain of the Park-Williams No. 8 diphtheria bacillus was found to require valine, leucine, methionine, cystine and glutamic acid, together with a tissue extract preparation, glycerol and suitable inorganic salts, in order to produce maximal growth. The same strain, in a period of 18 mos., carried in another laboratory, had acquired the additional need of glycine, but this latter strain readily adapted itself to the absence of glycine and could be passed serially on the first-mentioned medium, reaching in a week''s time the same maximum as that shown by our own strain. It is believed that strains of the Park 8 organism obtained from various sources may well show considerable differences in growth requirements.