436 PRINCIPLES OF SOIL MICROBIOLOGY 



Cellulase acts at temperatures of 20° to 70°. When a culture of 

 thermophilic bacteria acting at 55° is brought to room temperature, 

 the action of the living bacterial cells upon cellulose and the production 

 of gas stop but the enzyme action continues even at 20°. By a mere 

 change in temperature, active growth accompanied by gas formation 

 is discontinued; under these conditions enzyme action results in an 

 accumulation of sugar, as indicated by reduction of Fehling 's solution 

 and osazone formation. The cellulose is transformed into cellobiose 

 and the latter partly to glucose by the enzyme cellobiase, which is still 

 active at 20°. By raising the temperature to 67°, Pringsheim succeeded 

 in repressing both the growth of bacteria and the action of cellobiase, 

 leaving only cellulase active; this resulted in the accumulation of only 

 cellobiose. Groenewege 30 also demonstrated that bacteria hydrolyze 

 cellulose, by means of an enzyme cellulase, into cellobiose and the latter 

 is then hydrolyzed to glucose. In an alkaline medium, cellobiose is 

 formed faster than it is hydrolyzed. It is much easier to demonstrate 

 the formation of an enzyme decomposing celluloses by fungi. 31 



The glucose formed from cellulose by the action of the bacterial 

 enzymes is rapidly broken down by the same organisms or by accom- 

 panying forms to various organic acids, such as acetic, butyric and lactic 

 or formic, acetic and valeric (Groenewege). These acids are decom- 

 posed, either by the same bacteria or by a secondary flora, to carbon 

 dioxide and water. In the decomposition of sugars by the anaerobic 

 bacteria, methane, hydrogen and carbon dioxide are formed directly. 

 In some cases, the transformation of the cellulose leads to the forma- 

 tion of mucilages consisting of hemicelluloses. According to Neuberg 

 and Cohn, 32 acetaldehyde is formed as an intermediary product in the 

 decomposition of cellulose by thermophilic bacteria. It is this ace- 

 taldehyde which may serve as the building stone for the synthesis of 

 the microbial protoplasm. The formation of pigments in the decom- 

 position of cellulose is more characteristic of the organism than of the 

 cellulose. 



30 Groenewege, J. Untersuchungen liber die Zersetzung der Zellulose durch 

 aerobe Bakterien. Bull. Jard. Bot. Buitenzorg (3), 2: 287. 1920; Meddel. 

 Alg. Proefsta. Landbr. Dept. Nijv. Handel., 13: 1-23. 1923. 



31 Kellerman, K. F. Formation of cytase by Penicillium pinophilum. U. S. 

 Dept. Agr., Bur. PI. Ind. Circ. 113, 1912; Ellenberger, W. Zur Frage der Cellu- 

 losverdauung. Ztschr. physioi. Chem., 96: 236-254. 1915; Kosin, N. I. On 

 the aerobic decomposition of cellulose by fungi. Rpt. of the Physico-Chem. 

 Lomonossov Soc, Moskau, 2: 57-98. 1921. 



32 Neuberg, C, and Cohn, R. tJber Zwischenprodukte des bakteriellen Ab- 

 baues von Cellulose. Biochem. Ztschr., 139: 527-544. 1923. 



