176 



THE ACTINOMYCETES, Vol. I 



2 4 



Figure 75. Formation of plaques (Reproduced from: Woodruff, H. B. et at. J. Bacteriol. ol: 536 

 1947). 



some important ecionomic problems. The ly- 

 sis of the culture by phage appeared to be 

 quite distinct from that produced by auto- 

 lytic factors. Saudek and Colingsworth re- 

 corded in 1947 that the action of the trans- 

 missible lytic agent ui)on »S. griseus had all 

 the properties of phage. In young cultures 

 the phage developed rapidly and brought 

 about lysis of the mycelium. The plaque 

 method was used for measui'ing phage con- 



centration. Streptomycin production was 

 partly or completely stopped by the phage. 

 Cultures resistant to the phage action could 

 easily be isolated from phage-infected cul- 

 tures. 



By exposing suhmerg(>d cultures of S. gri- 

 seus, in a stationary condition, for 24 hours, 

 Woodruff et at. (1947) easily demonstrated 

 the presence of actinophages in the atmos- 

 ))here. Tpon transfer of a filtered broth into 



