180 



THE ACTINOMYCETES, Vol. I 



Figure 77. Phage particles adsorbed on a streptomyces spore (Reproduced from: Mach, F. Centr. 

 Bakteriol. Parasitenk. Abt. II; 111: 556, 1958). 



ophage in greenhouse soils. In four out of 

 fourteen samples of soil, free actinophages 

 were revealed by direct count. In most cases 

 these actinophages proved to be polyvalent. 

 In another ten samples of greenhouse soils 

 and in twenty-five samples of forest and 

 meadow soils, as well as in filtrates of field 

 soils, no free actinophage Avas found. Many 

 actinomycetes isolated from these soils were 

 susceptible to the eight different actino- 

 phages previously isolated. Mach (1958) iso- 

 lated from composts and forest litter three 

 actinophages of which two were polyvalent 

 and one strongly specific. These three phages 

 were morphologically distinct from one an- 

 other, as shown by the electron microscope. 

 Bradley and Anderson (1958) isolated 

 from soil three streptomyces phages and five 



nocardia phages. Of the former, one attacked 

 a culture designated as A'", paraguayensis, and 

 of the latter, three attacked streptomyces. 

 All other Actinomycetales were resistant to 

 both types of phage, as shown in Table 45. 

 On the basis of these results, the authors con- 

 cluded that the genera Nocardia and Strepto- 

 myces are closely related and should not be 

 separated into different families. Such gen- 

 eralization is hardly justified. The A^. para- 

 guayensis used in these tests is not a no- 

 cardia, but a streptomyces, as will be brought 

 out in Vol. II. The nocardia phages that 

 attacked the streptomyces cultures may 

 have been polyvalent phages, a potentiality 

 indicated in the early studies of Wieringa 

 andWeibols (19o(i). The sensitivity to phages 



