480 PRINCIPLES OF SOIL MICROBIOLOGY 



does not seem to have any influence upon the rate of transformation 

 of imino nitrogen into ammonia nitrogen. 



These results tend to indicate that a simple observation of the amount 

 and rate of ammonia formation need not necessarily indicate the course 

 of protein decomposition. A certain set of conditions will lead to the 

 formation of one group of compounds by bacteria from a certain pro- 

 tein, while another group of compounds will be formed from the same 

 protein under different conditions. It was also generally assumed 23 

 that the rapid oxidation of proteins may result in the liberation of 

 elementary nitrogen, according to the reaction: 



4 NH 3 + 3 2 - 6 H 2 + 2 N 2 



However, the work of Ehrenberg 24 pointed to the negligible loss of 

 nitrogen from this source. Appreciable losses may occur either through 

 direct volatilization of ammonia or by leaching of nitrates. 



Chemistry of ammonia formation in the decomposition of proteins by 

 microorganisms. Mtintz 25 was the first to demonstrate in 1890 that 

 organic matter is decomposed by organisms with the formation of 

 ammonia, which is only then nitrified. In soils in which nitrification 

 has been stopped by the use of heat or disinfectants, ammonia accu- 

 mulates, indicating that this treatment was sufficient to kill the organ- 

 isms oxidizing ammonia to nitrate, but not those that produce ammonia 

 from proteins. Muntz and Coudon 26 have further shown that no 

 ammonia was formed during two and one-half years in sterilized soil, 

 while the unsterilized soil produced, in sixty-seven days, 41 to 100 

 mgm. of ammonia per 100 grams of soil. These investigations were 

 followed by those of Marchal 27 and numerous others which pointed 

 to the importance of ammonia formation in the soil and the role of 

 microorganisms in its formation from proteins. This was found to be 

 not a specific property of certain bacteria, but a function of a large 

 number of microorganisms. 



n Voorhees and Lipman, 1907 (p. 491), p. 49. 

 "Ehrenberg, 1907 (p. 268). 



26 Mtintz, A. Sur la decomposition des engrais organiques dans le sol. 

 Compt. Rend. Acad. Sci., 110: 1206-1209. 1890. 



"Miintz, A., and Coudon, H. La fermentation ammoniacale de la terre. 

 Compt. Rend. Acad. Sci., 116: 395-398. 1893. 



27 Marchal, E. Sur la production de Pammoniaque dans le sol par lea 

 microbes. Bull. Acad. Roy. Sci. Belg., (3), 25: 728-738; 27: 71-103. 1895; 

 Centrbl. Bakt. II, 1: 753-758. 1895. 



