PHYSIOLOGY OF MICROORGANISMS 57 



10. Enzyme Action 



The light portion of the plate is due to the presence of casein in the agar. The 



digesting enzyme has acted on the casein not only in contact with the bacteria 



which form the white streak, but on that a distance away. The enzyme has 



changed the casein to soluble products which can pass into the cells 



concerned. The processes that go on inside the cell, and 

 that are connected with the assimilation of the food, always 

 involve a loss of energy. 



The more varied the enzymes produced by an organism, 

 tlic more varied may its food be. For example, no organ- 

 ism that does not produce an enzyme that can change gela- 

 tin into soluble compounds can utilize this substance as food. 

 The classification and naming of enzymes is very confusing, 

 and need not be introduced here. The enzymes that act 

 on protein are commonly called proteolytic enzymes. Some 

 can act on a number of different proteins, others on only a 

 few. 



