TABLE II. 



93 



B.proteus 



B. liquifaciens . . 



B. subtilis 



B. megatherium 



Monoamino 

 Acid N. 



25.42 

 20.32 

 4.17 

 29.15 



Diamino 

 Acid N. 



76.29 

 75.40 

 67.83 

 69.40 



In general, this is in agreement with the work of Robinson and Tar- 

 tar (Journal Bio. Chem., Vol. XXX, page 135). However, this compar- 

 ison can only be roughly made since their medium consisted of an aqueous 

 soil extract plus a nitrogenous food material; i. e., fibrin, pepton, egg- 

 albumen, gliadin, and casein, with a small amount of carbohydrate in 

 the form of mannite and synthetic solution of salts in addition to the 

 salts extracted from the soil. 



The pure cultures used by Robinson and Tartar were B. mycoides, 

 B. subtilis, and B. vulgaris. The above facts concerning the utilization 

 of the amino acids by bacteria are in harmony with the work of most 

 investigators on bacterial metabolism. No doubt the utilization of the 

 amino acids is influenced by the character and quantity of proteins and 

 carbohydrates present in the media. We know, if carbohydrates are 

 absent or hydrolyzed into compounds which do not yield the desired food 

 material — namely, the carbon — as readily as the original carbohydrates, 

 bacteria, must necessarily derive their carbon supply from the protein 

 or amino acids. There is no quantitative relation connecting the in- 

 crease of acidity with the loss of carbohydrates by bacterial action on 

 the respective carbohydrates. So some of the carbohydrates must be 

 used in supplying energy to the organisms. 



About six years ago, while the senior author was conducting an 

 extensive investigation concerning the keeping qualities of butter when 

 placed in cold storage, the results of the investigation suggested to him 

 the advisability of taking up a systematic study of pure cultures of 

 known bacteria in a medium composed of milk proteins in presence of 

 carbon compounds such as lactose and lactic acid, etc. 



By pursuing this method of investigation it will be possible to arrive 

 at more definite information regarding the bacterial action on milk pro- 

 teins and the character and quantity of the final cleavage products. The 



