434 PRINCIPLES OF SOIL MICROBIOLOGY 



were two distinct processes, carried on by different organisms and 

 under distinctly different conditions. 



The anaerobic processes of cellulose decomposition may be conve- 

 niently divided into two groups. (1) In the absence of nitrate, the 

 cellulose may undergo a hydrogen or methane fermentation by anaero- 

 bic bacteria. (2) In the presence of nitrates, the cellulose is destroyed 

 by aerobic denitrifying bacteria. 



Under aerobic conditions cellulose decomposition was found to take 

 place in two ways. (1) If the medium is slightly alkaline, certain 

 aerobic bacteria and actinomyces will be most active. (2) If the 

 medium is acid, fungi are active in the decomposition of the cellulose. 



The microorganisms capable of decomposing cellulose can be divided 

 into seven general groups: (1) anaerobic bacteria, (2) aerobic bac- 

 teria, (3) thermophilic bacteria, (4) denitrifying bacteria, (5) actino- 

 myces, (6) fungi, and (7) possibly also invertebrate animals. 23 In 

 normal cultivated soils, the aerobic bacteria, fungi, and actinomyces are 

 largely concerned with the decomposition of celluloses. 2425 Under 

 anaerobic conditions, as in peat and cranberry bogs, anaerobic bacteria 

 are responsible for the decomposition of celluloses; while, in the 

 manure heap, thermophilic bacteria may be largely active. 



The true celluloses are digested by the herbivorous animals by means 

 of the bacteria present in their intestinal tract. 26 When stable manure 

 is added to the soil, large quantities of cellulose decomposing bacteria 

 are introduced. This has led to the claim that the addition of stable 

 manure is equivalent to inoculations of soil with strong cellulose de- 

 composing bacteria. It is doubtful, however, whether these organisms 

 could become active in the soil, even if all normal soils were not already 

 abundantly supplied with various types of organisms capable of de- 

 composing celluloses. 



To be able to demonstrate the nature of the decomposition of cellu- 

 lose by microorganisms, enzymes had to be obtained so as to allow the 

 investigation of the hydrolytic nature of the phenomenon. Some 



23 Younge, C. M. The digestion of cellulose by invertebrates. Sci. Progr. 

 No. 78: 242-248. 1925. 



24 Miitterlein, C. Studien liber die Zersetzung der Cellulose im Diinger und 

 im Boden. Inaug. Diss. Leipzig. 1913;|Waksman and Skinner, 1926 (p. 190). 



25 Pringsheim, H. Die Beziehungen der Zellulosezersetzung zum Stickstoff- 

 haushalt im der Natur. Centrbl. Bakt. II, 37: 111-112. 1913. 



26 Scheunert, A. Beitriige zur Kenntnis des Cellulosverdauung im Blindarm 

 und des Enzymgehaltes des Coecalsecretes. Ztschr. physiol. Chem., 48: 9- 

 26. 1908. 



