CHAPTER VIII 



Bacteria Capable of Decomposing Celluloses and Other 



Complex Carbohydrates and Hydrocarbons 



in the Soil 



Microorganisms concerned in the decomposition of celluloses in nature' 

 Among the microorganisms concerned in the decomposition of different 

 constituents of plant and animal tissues, those capable of breaking 

 down celluloses have attracted considerable attention, due to the fact 

 that these materials make up a large part of the bulk of the organic 

 matter added to the soil, but chiefly because the organisms concerned are 

 more or less specific in nature. Many bacteria are capable of existing 

 only with celluloses as a source of energy and some cannot even 

 utilize any other source of energy. Organisms capable of decomposing 

 celluloses are found among various groups of fungi, among the actino- 

 myces and among the bacteria. However, under anaerobic conditions, 

 the fungi and actinomyces do not thrive and bacteria alone are entirely 

 concerned in the process. 



The cellulose-decomposing bacteria can be divided into two groups, 

 (1) the aerobic and (2) the anaerobic forms. Certain special groups of 

 these forms may be concerned in the process, namely (3) the ther- 

 mophilic bacteria, probably active in the decomposition of celluloses 

 in manure and also in the soil under certain conditions, and (4) the 

 denitrifying bacteria, active only in the presence of nitrates and under 

 certain specific conditions. 1 



Anaerobic bacteria. Mitscherlich 2 observed in 1850 that, in the rot- 

 ting of potatoes in water, the cell walls are destroyed while the starch 

 accumulates at the bottom of the container. He ascribed this action to 



1 See Pringsheim, H. Die Polysaccharide. 2 Aufl. Springer. Berlin. 1923; 

 Karrer, P. Einfiihrung in die Chemie der polymeren Kohlenhydrate. Akad. 

 Verlagsges. Leipzig. 1926. Rippel, A. Der biologische Abbau der pflanz-, 

 lichen Zellmembrannen. Ztschr. angew. Bot. 1: 78-97. 1919; Waksman, S. A. 

 and Skinner, C. E. The microorganisms concerned in the decomposition of 

 celluloses in the soil. Jour. Bact. 12: 57-84. 1926. 



2 Mitscherlich. Zusammensetzung der Wand der Pflanzenzelle. Monatschr. 

 K. Akad. Wiss. Berlin. 1850, 102-110. 



190 



