Growth Factors in Relation to Development of Certain “Fastidious” Bacteria

Abstract

It is well known that many of the more fastidious bacteria require special media such as fresh meat infusions for their development and refuse to grow, or at best grow poorly, on the ordinary standard agar and broth made with peptone and meat extract. These organisms, almost without exception, also refuse to grow in a chemically definite or synthetic medium. The nature of the necessary substances in the more complex media is largely a matter of conjecture at present, although it constitutes one of the very important problems of bacterial nutrition.

In the present investigation we have attempted to separate from ordinary veal infusion the factors responsible for growth of some of the more exacting bacteria. It seems reasonable to suppose that a more exact knowledge of these substances would not only reveal many practical applications in bacteriological work but would also have a rather general biological significance.

The removal of growth factors from protein digests or infusions by the use of charcoal has been reported by Robinson and Rettger, 1 Thjotta and Avery, 2 Mueller, 3 and Freedman and Funk. 4 In our work it was found that treatment of an ordinary veal infusion with charcoal resulted in the removal of unknown substances necessary for the growth of certain microorganisms. Other commonly used adsorbents, such as Fuller's earth, kaolin, talc, Lloyd's reagent, filter paper, calcium phosphate, Supercel, or silica gel were relatively ineffective. The unknown substances or growth factors, after removal by charcoal from an infusion, could be recovered by extraction from the charcoal with hot ethyl alcohol or hot acetone.

These extracts, after evaporation of the alcohol or acetone and subsequent solution of the residue in water, were effective in “activating”an infusion from which growth factors had been removed, or in rendering a standard beef extract-peptone broth more suitable for growth of certain exacting organisms.