Chapter VI — 101 — Enzymes, etc. 



heated to 80°C., their activity is destroyed. When some of the cul- 

 tures are kept for a long time at 40°-45°C., the reproductive capacity of 

 the cells is destroyed, but their proteolytic functions are not injured 

 (234). The ability to cause proteolysis is more marked for the non- 

 pigmented forms than for the pigmented types. Beijerinck postulated 

 that the pigmented forms are responsible for a solidifying effect pro- 

 duced by the quinone upon the liquid gelatin. To what extent this is 

 responsible for the apparently lower proteolytic action of pigmented cul- 

 tures still remains to be determined. 



Table 18: Proteolytic activity of actinomycetes in 1 per cent gelatin solution (187): — 

 Results in milligrams of nitrogen per 25 ml of medium 



In some species, proteolysis occurs only at a late stage in the develop- 

 ment of the organism. This may be due to the formation of endoen- 

 zymes, which are liberated on the death of the cells, as contrasted with 

 the exoenzyme produced at an early stage of the development of the 

 mycelium. This explanation has not been universally accepted, how- 

 ever (234). Bacteriolvsis may often parallel growth inhibition (Table 

 19). 



The ability of certain actinomycetes to cause the lysis of various 

 bacteria is characteristic of certain species of Stre^ptamyces. This effect 

 directed upon plant pathogenic bacteria may be of considerable eco- 

 nomic importance. A culture designated as Streftomyces 105 which 

 produced a wine-colored soluble pigment and a white to gray aerial my- 

 celium was found (83) to exert a lysogenic effect upon various species 

 of Phytomonas, Erwinia, and other gram-positive and gram-negative 

 bacteria. Potato extract-glucose agar media were particularly favorable 

 to the production of the Ivtic agent. Cultures of Streftamyces 105 



