BACTERIA DECOMPOSING CELLULOSES 201 



nutrient agar plates. A small piece of the decomposing cellulose is 

 thoroughly disintegrated on the plate, by means of a sterile spatula. 

 If a large piece of paper is used, it should be previously washed in salt 

 solution, to wash off the rapidly growing organisms not taking part in 

 the processes of cellulose decomposition and nitrate reduction. These 

 organisms develop only slowly as minute colonies and the plates have 

 to be incubated for four to six days at room temperature, before trans- 

 fers can be made. In the presence of rapidly growing organisms the 

 minute colonies usually fail to develop. 



The bacteria isolated in the processes of cellulose decomposition and nitrate 

 reduction were divided 28 into three groups: (1) those which effected denitrifica- 

 tion in nitrate bouillon but not in the cellulose-KN03 (0.1 per cent) medium; 

 (2) those which did not reduce nitrates in the nitrate bouillon but caused re- 

 duction in the cellulose nitrate medium; (3) those which did not reduce nitrate 

 in either medium. A combination of the first two groups or of all three brought 

 about active reduction of nitrate and decomposition of cellulose. Group 1 was 

 found to consist of two bacteria, namely Bad. opalescens and Bad. viscosum; 

 group 2 consisted of three strains of Bad. cellar esolv ens (a very fine, aerobic, rod- 

 shaped organism), all of which grew very slowly and formed minute colonies on 

 nutrient agar. The cellulose decomposing organism was obligate aerobic. B. 

 cellar esolv ens attacked cellulose; the products of the decomposition (acetic, 

 butyric and lactic acids) could serve as food for the denitrifying organisms, B. 

 opalescens and B. viscosum. The complete process is one of symbiosis. 



For a quantitative study of cellulose decomposition, Groenewege used a 

 medium consisting of: 



Filter paper 200 mgm. CaC0 3 400 mgm. 



NH 4 C1 40 mgm. Tap water 40 cc. 



K 2 HP0 4 20 mgm. 



The medium was inoculated with pure cultures of the organisms and mixtures 

 of the cellulose decomposing and denitrifying forms. After three weeks, 10 cc. 

 of 10 per cent HC1 was added, flasks filled to half with water and after the cellulose 

 settled, the liquid was taken off. This was repeated until the liquid was free from 

 acid. The residue was then centrifuged, dried and weighed. The cellulose de- 

 composing bacteria alone decomposed 17 to 135 mgm. of the cellulose (depending 

 on strain) and 22 to 151 mgm. in the presence of the denitrifying bacteria. Sim- 

 ilar results were obtained with asparagine as a source of nitrogen, indicating that 

 the favorable influence of the B. opalescens on B. cellar esolv ens is due to a sym- 

 biotic action. 



Thermophilic bacteria. MacFayden and Blaxall 29 were the first to 

 demonstrate the presence in the soil of organisms which are able to 

 decompose cellulose at 60° to G5°C. The process was accelerated under 



29 Macfayden, A., and Blaxall, F. R. Thermophilic bacteria. Trans. Jenner. 

 Inst. Prevent. Med. Ser. 2: 162-187. 1899. 



