BACTERIA OF THE SOIL 241 



action of bacteria, a process the converse of that just dis- 

 cussed occurs. Water is inserted into the complex molecule 

 which then breaks apart at this point of cleavage forming 

 two molecules somewhat less complex. Bacteria which are 

 capable of attacking proteins and breaking them down in 

 this fashion by the introduction of water, that is, by hydrol- 

 ysis, are said to be proteolytic. Such organisms are com- 

 paratively common in the soil. Many of the spore-pro- 

 ducing bacteria, such as Bacillus subtilis and Bacillus 

 mycoides are of this character. The same kind of a change 

 may be brought about by some of the species of cocci and by 

 species of Actinomyces. The proteoses and peptones pro- 

 duced by these organisms are attacked by a still greater 

 variety of forms and broken down into simpler and simpler 

 compounds, eventually with the formation of considerable 

 amounts of alpha-amino acids. These amino acids, as they 

 develop, may be attacked by species of bacteria and molds in 

 the soil. One of the most common changes is that known as 

 ammonification, or more properly deaminization. Ammonia 

 is split off. In most instances apparently the microorgan- 

 ism is not primarily concerned with the ammonia which is 

 thus released, but has removed the amino group in order 

 that it may utilize the remainder of the acid as food. 



It is evident that not all of the nitrogen compounds which 

 gain access to the soil are in the form of plant and animal 

 protein. A considerable part, for example, of the nitrogen 

 in barnyard manure may be in the form of urea and liip- 

 puric acid. Many species of spore-producing bacteria in 

 particular are capable of attacking urea, bringing about 

 deaminization or ammonification in accordance with the 

 following reaction: 



(NH 2 ) 2 CO + 2H 2 = (NH 4 ) 2 C0 3 



Other nitrogenous compounds which may be added to the 

 soil such as hippuric acid, calcium cyanamide, etc., are 



