Waksman — 60 — Actinomycetes 



The colonies from the bovine strains were smoother and softer in 

 consistency and did not adhere to the medium. Growth was scantier. 

 The mycehum underwent fragmentation very rapidly, giving only 

 traces of extensive ramification. No aerial hyphae were produced. In 

 contrast to the human strains, the bovine strains showed occasional tur- 

 bidity in the medium, and they were less able to ferment sugars, espe- 

 cially salicin and mannitol. 



No filterable stage could be demonstrated by ultrafiltration experi- 

 ments on either the human or bovine strains, and no evidence could 

 be obtained in favor of any hypothetical life-cycle. 



Autolysis of actmomycetes.— Only a few actinomycetes are able to 

 show the phenomenon of autolysis. This was reported first for animal 

 pathogens (91) and later also for plant pathogens and for soil sapro- 

 phytes (509). The active agent responsible for the lysis was consid- 

 ered to be either an enzyme or a nontransferrable phage. 



Of 1,000 or more freshly isolated cultures of actinomycetes studied 

 by Krassilnikov (232) only very few were able to undergo lysis. An 

 organism described as A. albicans at first gave a typical heavy compact 

 growth covered with white aerial mycelium. On continuous transfer, 

 the colonies became flat, smooth, and somewhat moist and lost the 

 property of producing aerial mycelium. The culture was gradually re- 

 duced to a very thin slimy film. It grew more and more poorly, be- 

 coming, on repeated transfer, more rapidly transparent, until it finally 

 ceased to grow altogether. All attempts to keep it alive were unsuc- 

 cessful. Six other strains of a similar nature were isolated later. They 

 belonged to different groups and showed difl^erent degrees of lysis. 



Among actinomycetes, autolysis may not appear all through the 

 colony, but may affect only certain sectors or spots, the unlysed part of 

 the colony being quite distinct from the lysed part. Frequently lysis 

 begins in the center of the colony and proceeds to the periphery. 



The mechanism of autolysis among pathogenic forms is similar to 

 that of the saprophytes but proceeds more rapidly (232). Meat-peptone 

 agar is a favorable medium for the study of autolysis. When the cul- 

 ture is grown at 25 °C., plated out and incubated at 30° or 37° (for 

 pathogens), autolysis proceeds very rapidly; in fact, it becomes evident 

 in 4 to 6 hours. Not all the hyphae are lysed uniformly. Some pro- 

 duce chlamydospores, and others, spherical bodies, as well as hyphal 

 fragments. Under favorable conditions, all three types of bodies are 

 able to grow and develop into fresh colonies. 



The lytic factor is present within the cells of the actinomycetes. It 

 becomes active when growth ceases, although it is possible that there 

 is considerable overlapping of the two processes. When a growing cul- 

 ture is treated by physical or chemical agencies so as to stop growth, lysis 

 begins immediately. If the temperature of the culture is raised to 60° 

 — 70°C., autolysis occurs in a few minutes. The lytic factor is in- 



