HETEROTROPHIC BACTERIA REQUIRING COMBINED NITROGEN 159 



inorganic source of nitrogen and inoculated with a soil suspension, 

 if the cultures are placed under a bell jar together with a dish of 

 benzene or petroleum, and incubated at 30°C. The final isolation 

 and purification of the organisms can be accomplished by means of 

 ordinary bacteriological methods. Spore formation takes place by 

 contraction of the cell contents, in a manner similar to that of the 

 actinomyces (p. 294), giving coccus-like fragments. The colonies on 

 solid substrates have a certain thread-like structure (No. 43, PI. VIII). 



The organisms readily utilize various hydrocarbons as sources of 

 energy. 54 They do not form any ammonia from proteins; 53 most of them 

 reduce nitrates to nitrites (similar to actinomyces). Their role in the 

 soil seems to consist largely in the decomposition of certain organic 

 compounds. 



Myxobacteria. Mycobacteria occur abundantly in manure and 

 probably take a part in the decomposition of certain constituents of 

 natural organic materials. To demonstrate the presence of Myxo- 

 bacteria in the soil, balls of rabbit manure, previously moistened with 

 water and sterilized in the autoclave, are placed on the surface of the 

 particular layer of soil. Frequently 7-10 species are thus obtained 

 from one soil sample. 56 



5S Krzemieniewsky, H. and S. Die Myxobakterien von Polen. Acta Soc. Bot. 

 Poloniae. 4: 1-54. 1926. 



