Chapter IX — 151 — Decomposition of Residues 



Krainsky (230) divided all the actinomycetes, on the basis of their 

 ability to attack cellulose, into two groups: I. the macroactinomyces, 

 forming large colonies on agar and not decomposing cellulose at all or 

 only to a very limited extent; 2. microactinomyces, forming minute 

 colonies on agar and decomposing cellulose rapidly with the formation 

 of pigments. Rubentschik (372) demonstrated that certain actinomy- 

 cetes produce a melanin pigment in their attack upon cellulose. De- 

 composition of chitin is also carried out by various actinomycetes (398). 

 The formation of a clear zone on an agar plate was designated as chiti- 

 nolysis. Pathogenic forms are particularly capable of bringing about this 

 process. In addition to the pathogens, saprophytic forms, notably S. 

 grisetis, S. griseolus, S. aureus, S. exfoliatus, S. fradiae, are able to attack 

 chitins. 



In addition to the carbohydrates and organic nitrogenous com- 

 pounds, actinomycetes are able to decompose various steroids, such as 

 cholesterol (430), a variety of aromatic compounds (156), acetylene 

 (38), and many others. They are able to utilize numerous other or- 

 ganic compounds, such as agar, rubber, paraffins, and lignins, substances 

 known to be fairly resistant to attack by the great majority of bacteria 

 and fungi. Buttner (59), for example, demonstrated that various 

 aerobic actinomycetes are capable of attacking paraffin; decomposition 

 of the paraffin could be measured by the liberation of carbon as COo; 

 about one fifth of the carbon was used for cell synthesis. Stanier (408) 

 made a detailed study of the variability in agar-decomposing capacity of 

 S. coelicolor. Certain actinomycetes are able to attack building mate- 

 rials and bring about their destruction (271^. 



Decomposition of Complex Plant Materials:— Actinomycetes can 

 attack various plant and animal residues and bring about their decompo- 

 sition. In a study of the decomposition of alfalfa by different or- 

 ganisms, Waksman and Hutchings (469) found that 43 per cent of 

 the hemicelluloses and 23.2 per cent of the cellulose were decomposed 

 in 39 days. Nearly 20 per cent of the nitrogen was liberated as am- 

 monia, pointing to considerable protein decomposition, since much of 

 the nitrogen must have been used for the synthesis of cell material. 

 In 50 days only 9.3 per cent of the oat straw was decomposed and this 

 was largely at the expense of the hemicelluloses (24.5 per cent), since 

 only litde cellulose and lignin were attacked. Litde decomposition of 

 corn stalks took place. When some CaCOs or phosphate buffers were 

 added, however, the material underwent rapid decomposition. Three 

 pure cultures decomposing an average of 20 per cent of the total dry 

 material, attacked the water-soluble substances most heavily (30.5 per 

 cent), then the hemicelluloses (16.7 per cent) and the cellulose (5,4 per 

 cent). The most striking point, however, was the fact that the de- 

 cqmposition of the lignin in these materials was always associated with 

 the presence of the actinomyces. 



