DECOMPOSITION OF PROTEINS 491 



bacteria. For every milligram of ammonia formed 8.9 mgm. C0 2 were 

 liberated. Marchal concluded that Bac. rmjcoides is one of the most 

 common soil organisms and one that attacks proteins most energeti- 

 cally. It is favored by a temperature of 30°, complete aeration, slightly 

 alkaline medium and a slight concentration of nitrogenous substance 

 in solution. 



The work of Marchal was confirmed and further extended by numer- 

 ous investigators. 54 The great majority of soil organisms developing 

 on the plate were found to produce ammonia from proteins. The 

 gelatin-liquefying bacteria were found to be capable of inducing a 

 greater protein decomposition with a more abundant ammonia forma- 

 tion. 55 Since these organisms form at times more than 15 per cent of 

 the total number of soil bacteria (developing on the plate), they were 

 believed to do the initial work in rendering soluble the protein nitro- 

 gen in the soil, so that it might be further decomposed by the same or 

 other soil organisms. 56 Lipman and Burgess 57 tested a series of pure 

 cultures of bacteria for their ammonia-producing power, using various 

 nitrogenous substances in various soils. Bac. tumescens was found to 

 be the most efficient organism of all tested, although in some cases 

 greater efficiency was obtained for Bac. mycoides and Sarcina lutea. 

 Usually 20 to 30 per cent of the protein nitrogen was transformed into 

 ammonia in twelve days. 



Conn, 58 however, found that, in manured soil, the non-spore forming 

 bacteria are much more active than the spore forming organisms. 

 According to Waksman and Lomanitz, 59 Bac. cereus rapidly decomposes 

 proteins to amino acids while Bad. fluorescens acts largely upon amino 



" Severin, S. A. Die im Miste vorkommenden Bakterien und deren physi- 

 ologische Rolle bei der Zersetzung derselben. Centrbl. Bakt. II, 1: 97-104, 

 160-168, 799-817. 1895; 628-633. 1897; 7: 369-386. 1901; 13: 616-631. 1904; 

 Chester, F. D. The bacteriological analysis of soils. Delaware Sta. Bui. 65. 

 1904; Lohnis, 1905 (p. 120); Lipman, J. G. Chemical and bacteriological factors 

 in the ammonification of soil nitrogen. N. J. Agr. Exp. Sta. 19th Ann. Rpt. 

 1906, 119-188. 



M Gage, S. D. Contribution to the biochemistry of sewage purification; the 

 bacteriolysis of peptones and nitrate. Jour. Amer. Chem. Soc, 27: 327-363. 

 1905. 



M Voorhees, E. B., and Lipman, J. G. A review of investigations in soil bac- 

 teriology. Bui. 194, Office Exp. Sta., U. S. Dept. Agr. 1907. 



s7 Lipman, C. B., and Burgess, P. S. Studies on ammonification in soils by 

 pure cultures. Univ. Cal. Publ. Agr. Sci., 1: 141-172. 1914. 



" Conn and Bright, 1919 (p. 41). 



" Waksman and Lomanitz, 1925 (p. 379). 



