324 Bacteria in Relation to Country Life 



show very marked differences in their physiological 

 efficiency may be isolated. 



Not all of the organisms capable of changing urea 

 into ammonium carbonate produce urease. Some of 

 them seem to perform the work directly without the 

 intervention of an enzyme, and are not capable, for 

 this reason, of accomplishing as much change in a given 

 time as some of the others. It should be added here, also, 

 that some of the uro-bacteria produce spores and are 

 capable of resisting unfavorable changes of tempera- 

 ture and concentration. Quantities of ammonium 

 carbonate that would prove destructive to other or- 

 ganisms do not appear to injure them at all. They sur- 

 vive when the concentration of the liquid excreta is 

 very marked. 



Other ammonia-forming bacteria. — Apart from the 

 uro-bacteria proper, ammonia may be produced from 

 the nitrogenous substances in manure by other species 

 of microorganisms. As in' the case of the protein sub- 

 stances in the soil-humus, the corresponding compounds 

 in the manure are gradually broken down with the for- 

 mation of ammonia as one of the cleavage products. 

 The inertness of the solid excreta and of the litter does 

 not allow as extensive a formation of ammonia as takes 

 place in the liquid excreta. Nevertheless, the inert 

 nitrogenous substances in the manures do undergo decay 

 slowly and may lead to appreciable losses of ammonia. 



Importance of ammonification. — Generally speaking, 

 therefore, ammonification, whether occasioned by the 

 rapid transformation of urea and hippuric acid by uro- 

 bacteria, or by the more gradual change of undigested 



