48 BACTERIOLOGY 



that cultures of bacillus prodigiosus, sterilized by heating 

 to 60° C, caused a solid coagulation of sterile milk in a few 

 days. 



A small number of bacteria have also been encountered 

 that bring about coagulation of milk with a distinctly 

 alkaline reaction. This function has been noticed in bac- 

 teria isolated from milk, and especially in bacterium pseudo- 

 diphtheriticum isolated from cows' milk (Bergey). 



Sugar-splitting enzymes are very common in bacteria. 

 This function varies in different species as seen in the dif- 

 ferent end-products that are formed. Buchner- succeeded 

 in isolating the sugar-splitting enzyme (zymase) of yeast- 

 cells, and when thus isolated it still possesses the power 

 of inducing active fermentation of sugar. It is believed that 

 the sugar-splitting enzymes of bacteria are similar in charac- 

 ter to the zymase of yeast-cells. The splitting up of carbo- 

 hydrates appears to be brought about by the bacteria for 

 the purpose of obtaining oxygen, as indicated by the nature 

 of the end-products formed, and also by the conditions 

 under which it may be carried out — i. e., the absence of 

 atmospheric oxygen. 



The splitting of the carbohydrate molecule may be illus- 

 trated as follows: 



CsHkOs = 2C2H6O + 2CO2 

 Grape sugar = 2 alcohol + 2 carbon dioxide 

 or CeHiiOs = 2C3H8O3 



Grape sugar = 2 lactic acid 



or CeHizOs = SCsHjOz 



Grape sugar = 3 acetic acid 



According to Theobald Smith' all facultative anaerobic 

 bacteria^ form acids from carbohydrates, while the strictly 



' Centralblatt fiir Bacteriologie, Bd., xviii. 

 2 See "aerobic" and "anaerobic" bacteria. 



