Studies on Bacterial NutritionThe Utilization of Nitrogenous Compounds of Definite Chemical Composition

The work of Bainbridge (1911) demonstrated that purified unaltered animal proteins, when supplied as the sole source of nitrogen, failed to furnish the necessary conditions for the development of certain aerobic and facultative anaerobic bacteria. This was substantiated by Sperry and Rettger (1915) who showed, in addition, that the putrefactive anaerobes were unable to attack native proteins and that pure vegetable proteins, as edestin, exhibited the same resistance to direct bacterial attack. They considered this resistance to be due to the complex construction of the protein molecule, which rendered it unfit for immediate utilization. Rettger, Berman, and Sturges (1916) found that coagulated albumin shows the same resistance to the direct action of bacteria as do the unchanged native proteins. They also demonstrated that proteose and peptones are not attacked, or at least very slowly, by the gelatin nonliquefying species. On the other hand, the organisms elaborating a proteolytic enzyme accomplished the destruction of these substances quite readily. Attention will be directed in this paper to the amino-acids and other simple nitrogenous compounds, for it is to these substances that one must turn to find sources of immediately available nitrogen. Several investigators have obtained striking results by employing proteinfree mediums composed of a mixture of the products of enzymatic protein cleavage. Dalimier and Lancereaux (1913) made use of a product known commercially as opsine. They succeeded in cultivating not only the commoner saprophytes but also many of the more exacting pathogens, as B. typhosus, B. diphtheriae, B. anthracis, B. tetani, B. tuberculosis (human, bovine and avian), the pneumococcus, meningococcus, and gonococcus. Robinson and Rettger (1918), in a more extensive study of opsine, were able to cultivate the obligate anaerobes, the Welch bacillus and many other exacting pathogens, in addition to the above-mentioned organisms. They also found that better results were obtained with the enzymatic digestion products of pro-