CHAPTER XIX 



ZYMOGENIC BACTERIA 



Introduction. Definitions. There are certain species 

 of bacteria which secrete within their cell protoplasm enzymes 

 or ferment-like substances. The amount of enyzme pro- 

 duced by a bacterium is modified by the quality and the 

 amount of the food which it receives. When grown upon a 

 medium containing proteins, the bacteria produce proteolytic 

 enzymes in excess. When grown upon a substance contain- 

 ing carbohydrates, amylolytic enzymes are produced. No 

 enzymes are produced without organic food of some char- 

 acter. 



The term "zymogenic" has been applied to those bacteria 

 which produce amylolytic enzymes capable of fermenting 

 carbohydrate compounds. Fermentation, as will be pointed 

 out later, is a distinct enzyme process. As a matter of fact, 

 all processes in which the enzymes of various kinds are con- 

 cerned are modified fermentations. The first important 

 work on the subject of fermentation was done by Pasteur in 



1857- 



The zymogenic bacteria in our subsequent discussions will 

 be considered to be those bacteria whose metabolic processes 



