Studies on isolation of Actinophage(S) from the Egyptian soil

A total of 110 soil samples collected from different localities of Egypt, were examined for their actinophage contents.The chloramphenicol-transforming Stireptomyces griseus (NRRL B-8O78) was selected as a host strain.Each of the soil samples was assayed by two methods, namely direct and specific enrichment ones. Phage assay, plaque forming units (PFU) was by the convential double layer technique. Only the speci¬fic enrichment method was proved to be very efficient Thus the direct method gave no plaques, whereas the specific enrichment (incubation 24 hours) gave an actinophage titer of; 1,5 x 10 PFU/one gram soil.On the other hand specific enrichment (5 days incubation) gave only. O.5 x 10 PFU/one gram soil.Out of the 110 soil Samples screened, only one sample (collected from Ismalia) yielded one actinophage nomenated on its host Streptomyces griseus as (SGPl). Considering the large number of the soil samples tested, one might speculate that s. griseus is apparently rich in certain endonucleases which prevent plaque formation.