164 Bacteria in Relation to Country Life 



Enzymes. — In Order to hasten the solution of the 

 protein, many bacteria produce chemical ferments 

 called "enzymes." The latter are like the pepsin, or 

 trypsin, produced for the same purpose in the animal 

 system. The bacteria, Hke animals, must digest their 

 food before they can assimilate it. However, animals 

 digest their food after it is eaten, whereas the bacteria 

 digest their food before it is eaten. In other words, 

 the animals have special organs in which the processes 

 of digestion are conducted, while the bacteria, as single 

 cells, have no special digestive organs; hence, the soluble 

 enzymes produced by them pass out through the cell- 

 wall and cause a chemical change in the protein sub- 

 stances that happen to be present in the material in 

 which the bacteria are developing. 



The bacteria possessing the ability to produce en- 

 zymes are known as "peptonizing" organisms. Peptone 

 is one of the products formed in the breaking down of 

 protein by means of enzymes. It is soluble and much 

 more simple in composition than protein, and is readily 

 changed still further with the production of ammonia. 

 Since the bacteria differ not only as to the amount, but, 

 also, as to the quality of the enzymes produced by them, 

 they must, necessarily, show marked differences in their 

 ability to decompose protein substances. 



Mutual relations of bacteria. — The decomposition of- 

 protein substances and the production of ammonia 

 should not be regairded as the result of the independent 

 activities of several kinds of bacteria. Living in the same 

 soil with many other species, each kind is influenced by 

 its neighbors. The struggle for existence develops a 



