BACTERIA REDUCING NITRATES AND SULFATES 183 



trites. Beijerinck and van Delden 19 found that various bacteria, like 

 Bac. subtilis and Bac. mesentericus vulgatus, are capable of producing 

 both ammonia and nitrite from nitrates, but no ammonia from nitrites; 

 Azotobacter chroococcum, however, produced ammonia from nitrates and 

 nitrites. The reduction process takes place in the presence of carbo- 

 hydrates and organic acids as sources of carbon. 20 These bacteria 

 undoubtedly include the "protein-forming bacteria" described by 

 Gerlach and Vogel, 21 capable of transforming nitrate into protein nitro- 

 gen with an intermediate reduction to ammonia nitrogen. 



Kruse 22 called attention to the fact that those microorganisms, which 

 cannot bring about "fermentation of the nitrate" (complete reduction 

 to nitrogen), are capable of reducing it to ammonia. This seems to be 

 the natural process, when microorganisms are assimilating nitrates and 

 nitrites, to reduce them first to ammonia, as shown for a number of 

 bacteria and fungi. 23 



Bacteria reducing nitrates to atmospheric nitrogen. The formation of 

 gaseous nitrogen in the process of decomposition of organic matter in 

 the soil was first observed by Davy. 24 This was ascribed to a chemical 

 interaction between nitrites and amino acids in the soil, resulting in 

 the formation of gaseous nitrogen. 25 Gayon and Dupetit 26 pointed out 

 in 1882 that bacteria were responsible for this process and that the free 

 nitrogen originated from the nitrates. Deherain and Maquenne 27 

 demonstrated that nitrate decomposition in the soil takes place only in 

 the absence of atmospheric oxygen and in the presence of an abundance 



19 Beijerinck, M. W., and van Delden, A. tJber die Assimilation des freien 

 Stickstoffs durch Bakterien. Centrbl. Bakt. II, 9: 3-43. 1902. 



20 Stoklasa, J., and Vitek, E. Beitrage zur Erkenntnis des Einflusses verschie- 

 dener Kohlenhydrate und organischer Sauren auf die Metamorphose des Nitrats 

 durch Bakterien. Centrbl. Bakt. II, 14: 102-118. 1905. 



21 Gerlach and Vogel. tlber eiweissbildende Bakterien. Centrbl. Bakt. II, 

 7: 609-623. 1901. 



22 Kruse, 1910 (p. xii). 



23 Kostyschew, S., and Tswetkowa, E. Uber die Verarbeitung der Nitrate in 

 organische Stickstoffverbindungen durch Schimmelpilze. Ztschr. physiol. 

 chem. Ill: 171-200. 1921. 



24 Davy, 1814 (p. 122). 



26 Dietzell, B. E. Ueber die Entbindung von freien Stickstoff bei der Faulnis. 

 Ztschr. Landw. Ver. Bayern. 72: 186 201. 1882. (Biederm. Centrbl. Agrik. 

 Chem. 11: 417-420. 1882). 



26 Gayon and Dupetit, 1882 (p. 181). 



27 Deh6rain, P. P., and Maquenne. Sur la reduction des nitrates dans la terre 

 arable. Compt. Rend. Acad. Sci. 95: 691-693, 732-734, 854-856. 1882. 



