Waksman 



66 



Actinomycetes 



These results show that the plates do not have to be heavily inocu- 

 lated with S. grisetis in order to give uniform growth on the plate of the 

 organism subject to attack by phage, with the resultant formation of 

 plaques. 



Actinophage of S. griseus was found to attack only the streptomycin- 

 producing strains of this organism. It had no effect on other strains 

 of S. grisezis or on other streptomycin-producing organisms such as S. 



Table 6: Effect of phage upon the growth, phage multiplication, and streptomycin production by 

 different actinomycetes in stationary cultures (355) : — 



* Each 60-ml llask of c 



1 of M-1 pha^e, i 



ing to 7 X 10" particles per 1 ml of medium. 



bikiniensis. In cultures that do not produce streptomycin, the phage 

 did not multiply and in some cases was destroyed or absorbed (Table 

 6). This actinophage multiplies only at the expense of the living cul- 

 tures of S. griseus but not on the heat-killed organism. Its optimum 

 temperature for multiplication is 28 °C., and it does not grow at 37 °C. 

 or above. However, it can withstand a temperature of 75 °C. for 1 

 hour but is completely destroyed when heated at 100°C. in 10 minutes. 

 When it is stored at 6''C., there is little loss of activity, but storage at 



