BIOLOGICAL FORMATION OF METHANE 



this problem by isolating pure cultures of cellulose-fer- 

 menting bacteria derived from soil. This approach proved 

 to be unexpectedly difficult and was finally abandoned. 

 Omelianski then tried more indirect methods. By analysis 

 of the gas formed by various cellulose-fermenting enrich- 

 ment cultures, he found that the ratio of hydrogen to 

 methane varied greatly from culture to culture. Ultimately, 

 by a combination of heating and transferring procedures, 

 he was able to obtain cellulose-fermenting cultures pro- 

 ducing either methane without hydrogen or hydrogen 

 without methane. Both cultures appeared to contain only 

 spore-forming bacteria which were similar in appearance. 

 The organism presumed to be responsible for the formation 

 of methane from cellulose was given the name of Bacillus 

 methanigenes. 



Omelianski's conclusion that he had demonstrated the 

 existence of a cellulose-fermenting, methane-forming bac- 

 terium may be correct but is open to doubt. The descrip- 

 tion of Omelianski's methods shows that he was not dealing 

 with pure cultures. Consequently the possibility cannot 

 be excluded that the observed methane formation was 

 the result of the action of two types of bacteria, similar 

 in morphology but differing in physiology. Subsequent 

 research has provided no confirmation of Omelianski's con- 

 clusion; none of the cellulose-fermenting bacteria since 

 isolated in pure culture has been found to produce methane. 



The Methane Bacteria 



The formation of methane in decomposing organic mate- 

 rials is the result of the action of a specialized physiological 

 group of bacteria, often referred to as the "methane-pro- 

 ducing bacteria" or, more simply, as the "methane bacteria." 

 These bacteria are entirely different from the aerobic 

 methane-oxidizing bacteria. The former produce methane 



