SOIL ACTINOMYCES 309 



none or scant growth on blood agar and egg- 

 media A. halstedii 



(b) Growth orange colored on most synthetic and organic 



media; aerial mycelium pink A. f radii 



(c) Growth yellowish on synthetic and glucose agars; pinkish 



to cinnamon-colored on calcium malate agar; no growth 

 on blood serum and egg media; none or only very scant 

 and late aerial mycelium on most media. A. alboflavus 



(d) Growth on synthetic media rose to red colored, aerial my- 



celium white, no visible action on milk. .A. albosporeus 



Over fifty species of actinomyces have been isolated from the soil and 

 described. 59 A much larger number, however, can readily be obtained 

 from the soil. Some of them are of wide occurrence, as the A. chromo- 

 genus types (A. viridochromogenus, A. pheochromogenus, etc.), A. aureus, 

 A. rutgersensis, A. violaceus ruber. 60 



Importance of actinomyces in the soil. Actinomyces take an active 

 part in the decomposition of organic matter in the soil, both of a nitrog- 

 enous and non-nitrogenous nature. Some species are capable of de- 

 composing celluloses very rapidly and there is no doubt that under 

 conditions favoring their development, as in neutral or alkaline and 

 arid soils or with insufficient moisture, actinomyces play an important 

 part in this process. Krainsky even divided all the actinomyces into 

 two groups: (1) the macro-actinomyces, forming oval spores and large 

 colonies on agar and not decomposing cellulose or only to a very limited 

 extent; and (2) the micro-actinomyces, forming spherical spores and 

 minute colonies on agar and decomposing cellulose rapidly with the 

 formation of pigments. Mace 61 pointed out that actinomyces decom- 

 pose proteins into amino acids and ammonia; he suggested that they 

 may bring about the formation of humus (ulmic acids) in the soil. Ac- 

 tive protein decomposition by actinomyces has also been recorded. 62-64 

 In view of the fact that the amount of mycelium synthetized by this 

 group of organisms is considerably smaller than that of fungi, only small 

 amounts of nitrogen are assimilated and most of it is liberated free in 



"Krainsky, 1914 (p. 288). Waksman and Curtis, 1916 (p. 290). Conn, 1917 

 (p. 288). 



60 A detailed description of various actinomyces found in the soil is given by 

 Waksman, 1919 (p. 288) and Bergey, 1923 (p. x). 



61 Mace, E. De la decomposition des albuminoides par les Cladothrix (Actino- 

 myces). Compt. Rend. Acad. Sci., 141: 147. 1905. 



62 Fousek, 1913 (p. 40). 

 "Munter, 1914 (p. 298). 

 "Waksman, 1919 (p. 288). 



