THE GROWTH OF BACTERIA IN PROTEIN-FREE 

 ENZYME- AND ACID-DIGESTION PRODUCTS 



HAROLD C. ROBINSON and LEO F. RETTGER 



From the Sheffield Laboratory of Bacteriology and Hygiene Yale University 

 Received for publication March 20, 1917 



The advantages of protein-free synthetic media for biochemical 

 study were appreciated early in the history of bacteriology. 

 With a medium the chemical composition of which is known it 

 should be possible to determine by exact study the chemical 

 nature of the products of bacterial growth. In the complex 

 peptone and infusion media this is impossible. 



Many synthetic media have been devised, most of them con- 

 taining several inorganic salts, and having glucose or glycerol 

 as the source of carbon, and organic ammonium salts, asparagin 

 or glycocoU as the source of nitrogen. Among the most important 

 of the earlier media were those of Cohn, Nageli, Frankel, and 

 Uschinsky. The chief difficulty with all of these, however, is 

 that only a limited number of bacteria will grow in them. The 

 more delicate and fastidious of the pathogenic class apparently 

 do not find proper nutriment in such simple media. B. diph- 

 theriae either refuses to develop or grows very slowly. Many 

 other organisms show the same indifference. 



With the discovery of the value of protein digestion products, 

 and particularly the amino acids, in animal nutrition, these 

 substances assumed much importance in the field of bacterial 

 metabolism. It has been demonstrated that all proteins must 

 first be reduced by the digestive secretions to the amino acid 

 stage before they can be utilized in animal cell metabolism. 

 Based on a similar assumption, protein hydrolysis products 

 and mixtures of amino acids have been in a few instances used as 

 culture media for bacteria. ^ 



^ For a somewhat comprehensive historical review of this subject the reader is 

 referred to the doctorate thesis of one of the authors (Robinson) in the Yale 

 University Library. 



209 



THE JOURNAL OF BACTERIOLOGY, VOL. Ill, NO. 3 



