376 MICROBIOLOGY OF SOIL 



investigators ascribed the decomposition of cellulose to an organism 

 found by Trecul in decomposing vegetable materials, and named by 

 him Amylobacter in 1865, because of the blue color assumed by it when 

 stained with iodine. 



Subsequent investigations by Omelianski begun in 1894 and con- 

 tinued through a period of years demonstrated the presence of specific 

 anaerobic organisms in decomposing cellulose. He described two dis- 

 tinct species of long, slender bacilli, assuming the clostridium form when 

 in the spore stage. Morphologically the organisms can hardly be dis- 

 tinguished, but physiologically they show important differences in that 

 one causes the fermentation of cellulose with the production of gases 

 consisting of carbon dioxide and methane, while the gases produced by 

 the other consist of carbon dioxide and hydrogen; hence the one is desig- 

 nated by Omelianski as the methane bacillus and the other the hydro- 

 gen bacillus. These organisms do not stain blue with iodine, and do not 

 belong, therefore, to the butyric bacilli designated as Amylobacter by 

 earlier investigators. Omelianski's investigations make it appear that 

 the butyric organisms are not capable of fermenting cellulose proper. 



In culture solutions containing mineral salts and nitrogen in the form 

 of ammonium compounds the decomposition of filter-paper and other 

 forms of cellulose proceeds with considerable rapidity. Calcium car- 

 bonate must be added to neutralize the acids formed, otherwise the 

 fermentation soon comes to a standstill. In one of Omelianski's experi- 

 ments begun in October, 1895, and ended in November, 1896, 3.3471 

 g. of cellulose was decomposed by a nearly pure culture of hydrogen 

 bacilli. The products consisted of 2.2402 g. fatty acids, .9722 g. carbon 

 dioxide and .0138 g. of hydrogen, a total of 3.2262 g. which nearly 

 accounts for all of the cellulose destroyed. The fatty acids were made 

 up of butyric and acetic acids with a slight proportion of some higher 

 homologue, probably valerianic acid. 



In a similar experiment with an apparently pure culture of the 

 methane bacillus, begun in December, 1900, and ended in April, 1901, 

 fermentation began after an incubation period of about one month, and 

 the entire volume of gas gradually evolved was 552.2 c.c. This mix- 

 ture consisted of 190.8 c.c. methane and 361.4 c.c. carbon dioxide. The 

 products formed from the 2.0065 cellulose consumed included 

 1.0223 g. fatty acids, .8678 g. carbon dioxide and .1372 g. of methane, 

 or a total of 2.0273 g- The slight difference in weight in favor of the 



