120 PRINCIPLES OF SOIL MICROBIOLOGY 



can be utilized as sources of energy. The available evidence seems to 

 indicate that celluloses may be utilized as sources of energy, when 

 cellulose decomposing bacteria are present, but not directly. 77 Ammo- 

 nium salts are utilized more readily than nitrates as sources of nitrogen. 

 Only traces of minerals are required, but the organism can withstand 

 as much as 10 per cent MgS04. It resists drying very readily and is 

 sensitive to high temperatures: the cells are destroyed in a few minutes 

 at 55°C, but resist drying for many years. 78 



Other non-symbiotic nitrogen-fixing bacteria. In addition to the CI. 

 pastorianum and the Azotobacter group, various other bacteria are 

 capable of fixing appreciable quantities of nitrogen, as pointed out by 

 Beijerinck and van Delden for a freshly isolated culture of Bacillus 

 mesentericus, and for a number of species of the aerobic Granulobacter. 

 The same is true of Bact. lactis viscosum, Bad. pneumoniae, Bad. 

 radiobader and Bact. prodigiosum?^ Bad. aerogenes, Bact. pyocyaneum 

 and a number of other bacteria were also found capable of fixing 

 small amounts of nitrogen, especially when freshly isolated from the 

 soil. The claims that various spore-forming bacteria, like Bac. sub- 

 tilis, Bac. megatherium, etc., are also capable of fixing nitrogen were 

 found to be unfounded. However, two representatives of the Bac. 

 mesentericus group, namely Bac. malabarensis and Bac. danicus, the 

 first isolated from South Indian rice soil and the second from 

 nodules of Vicia, were found capable of fixing nitrogen. Bact. radi- 

 cicola, the legume organism, can live in the soil outside of the 

 nodules and may fix small quantities of atmospheric nitrogen on artificial 

 media. 80 As much as 1.2 mgm. nitrogen may be fixed per 100 cc. of 

 medium. 81 Bac. asterosporus can fix 1 to 3 mgm. nitrogen for every 



. 77 Pringsheim, H. fiber die Verwendung von Cellulose als Energiequelle zur 

 Assimilation des Luftstickstoffs. Centrbl. Bakt. II, 23: 300 308. 1909; 26: 

 222-227. 1910; Biol. Centrbl. 31: 65. 1911; Hutchinson and Clayton, 1918 

 (p. 196). 



78 Stapp, C, and Ruschmann, G. Zur Biologie von Azotobacter. Arb. Biol. 

 Reichsaust. Land. u. Forstw. 13: 305-368. 1924. 



79 Lohnis, F. Beitrage zur Kenntnis der Stickstoffbakterien. Centrbl. 

 Bakt. II, 14: 582-604. 1905. Lohnis, F., and Pillai, N. K. fiber stickstoff- 

 fixierende Bakterien. II. Centrbl. Bakt. II, 19: 87-96. 1907; 20: 781-799. 

 1908. 



80 Lohnis, 1910 (p. 28); Lipman and Fowler, 1915 (p. 129). 



81 Fred, E. B. The fixation of nitrogen by means of Bacillus radicicola without 

 the presence of a legume. Va. Agr. Exp. Sta. Ann. Rpt. 1909-1910, 138-142. 



