On the Preparation of Salt-free Culture Media and the Growth of Bacteria upon Them

Some time ago I entered upon a study of the relations of different salts and nutrients to the metabolism of bacteria. The first step in the investigation lay in the preparation of a salt-free culture medium. A perusal of the literature indicated that the preparation of such a medium had never been really at tempted with natural nutrients; and all the work upon the influence of particular salts upon bacteria is rendered of doubtful value by reason of the fact that the salt in the culture medium was not controlled or removed. For this failure technical reasons have been directly responsible. A culture medium containing natural nutrient materials cannot be controlled in its content of salt. Culture media composed of some amido body, as asparagin, plus a sugar, may be prepared in such a manner as to permit of a control of the salts. But by chemical procedures it is not possible to determine the saline content of a culture medium containing natural nitrogenous substances, nor is it possible to eliminate the salts. Thus far few results of importance have been secured in this investigation beyond the technical preparation of a saltfree medium; and these are herewith reported in the hope that they may prove of service to others engaged in research along similar lines.