Observations on bacterial metabolism

Abstract

In the course of an investigation of the cultural requirements of certain of the pathogenic bacteria, a substance which occurs in meat infusion, and also in some of the proteins has been found to be essential for the growth of the streptococcus, and for certain strains of the pneumococcus. While it has thus far not been possible to isolate the compound in pure form, perhaps enough has been learned of its occurrence and properties to warrant a short note.

If an infusion of beef, or better, of beef heart muscle be prepared by boiling a pound of the chopped muscle in a liter of water, straining and filtering, and if 0.1 per cent. glucose and a nitrogen free inorganic salt mixture be added, it is found that the broth thus prepared is quite suitable for growth of the hemolytic streptococci. A P_H of 7.2-7.6 is most favorable, and no peptone or other nitrogenous material need be added. If, however, the meat infusion be mixed with 2 per cent. of wood charcoal, of the commercial brand called “Norit,” and boiled for fifteen minutes and filtered, the streptococcus will no longer grow on the filtrate, after adding glucose, and salts, and adjusting the reaction. Evidently a substance has been quantitatively removed from the infusion by the charcoal which is required by the streptococcus for growth. The addition of I per cent. commercial peptone to such a charcoal treated infusion now renders it again suitable for growth, although the peptone itself, plus glucose and salts, will not give growth with the streptococcus.

Since the material which is removed by the charcoal is apparently present in commercial peptone, it seemed most probable that an amino-acid or polypeptide was in question.