BACTERIA REDUCING NITRATES AND SULFATES 181 



This process was found to be brought about by various groups of micro- 

 organisms, capable of reducing nitrates to nitrites, first by Schonbein 2 

 in 1868, then by others, especially by Gayon and Dupetit. 3 In addition 

 to various bacteria, 4 certain yeasts, filamentous fungi, 5 and actinomyces 6 

 are capable of reducing nitrates to nitrites. The composition of the 

 medium is important in this respect, particularly the nature of other 

 sources of nitrogen and of the energy source. The presence of carbo- 

 hydrates, glycerol and organic acids, in addition to peptone, was found 

 to stimulate the reduction of nitrate to nitrite, while an abundance of 

 oxygen injured it. 



Frankland 7 called attention to the fact that certain bacteria {Bac. 

 ramosus and Bac. pestifer) are specifically concerned in this process. 

 The reduction was favorably influenced by increasing the organic 

 matter content of the solution, especially the peptone. Anaerobiosis 

 or lack of sufficient aeration greatly favors nitrite formation. 8-10 

 Nitrite-forming bacteria are well distributed in the soil. 11,12 Such soil 

 forms as Bac. megatherium 13 and Bad. vulgare u are found among the 



2 Schonbein, C. F. tJber die Umwandlung der Nitrate in Nitrite durch Confer- 

 ven und andere organische Gebilde. Jour, prakt. Chem. 105: 208-214. 1868. 



3 Gayon, U., and Dupetit, G. Sur les fermentations des nitrates. Compt. 

 Rend. Acad. Sci. 95 : 644-646. 1882; Sur la transformation des nitrates en nitrites. 

 Ibid., 1365-1367; Recherches sur la reduction des nitrates par les infiniments 

 petits. Nancy. 1886; Mem. Soc. Sci. phys. Nat. Bordeaux. 1886; Ann. Sci. 

 Aeron. 1: 226-325. (1885) 1886. 



4 Maassen, A. Die Zersetzung der Nitrate und Nitrite durch die Bakterien. 

 Arb. K. Gesundheitsamt, 18: 21-77. 1901. 



5 Wolff, K. Denitrifikation und Garung. Hyg. Rundschau, 91: 538. 1899. 



6 Waksman, 1919 (p. 299). 



7 Frankland, P. J. The action of some specific microorganisms on nitric acid. 

 Chem. News, 57: 89. 1888; Uber einige typische Mikroorganismen im Wasser 

 und im Boden. Ztschr. Hyg. 6: 373. 1899. 



8 Laurent, E. Experiences sur la reduction des nitrates par les vegetaux. 

 Ann. Inst. Past. 4: 722-744. 1890. 



9 Kiihl, H. Beitrag zur Kenntnis des Denitrifikationsprozesses. Centrbl. 

 Bakt. II, 20: 258-261. 1908. 



10 Caron, H. V. Untersuchungen uber die Physiologie denitrifizierender 

 Bakterien. Centrbl. Bakt. II, 33: 62-116. 1912. 



11 Jensen, 1897 (p. 180). 



12 Klaeser, M. Die Reduktion von Nitraten zu Nitriten und Ammoniak durch 

 Bakterien. Centrbl. Bakt. II, 41: 365-430. 1914: Ber. deut. bot. Gesell. 32: 

 58. 1914. 



13 Stoklasa, 1898 (p. 104). 



14 Horowitz, A. Contribution a l'£tude du geare Proteus vulgaris. Ann. Inst. 

 Past. 30: 307-318. 1916. 



