Characterization of actinophages specific to Streptomyces deserti isolated from Sohag Governorate reclaimed soils

Abstract

The purpose of this study was to isolate and characterize actinophages specific to Streptomyces deserti. First, the antifungal activity of Streptomyces deserti against Rhizoctonia solani was studied. Results indicated that Streptomyces deserti inhibited the fungal growth with 62%. Five actinophage isolates specific to Streptomyces deserti were successfully isolated from two different locations of reclaimed soil in Sohag Governorate. Electron micrographs of the isolated phages indicated that all the phage isolates appeared to be head-and-tail types. The five phage isolates were designated ФSD1, ФSD2, ФSD3, ФSD4 and ФSD5. Phage isolates were characterized using optimum multiplicity and found to be 1.0 PFU/CFU for phage isolates ФSD1, ФSD2 and ФSD3 and 0.5 PFU/CFU for ФSD4 and ФSD5. One-step growth curves were studied; all phage isolates had the same infection cycle period; the differences were in the latent period, rise period, and burst size. The thermal inactivation point of each phage isolate was studied. All phage isolates exhibited tolerance to high temperature, since they kept their activity at 100 °C for 10 minutes. The host range of all phage isolates was examined using fourteen Streptomyces spp. isolates; the optimum pH for phage infection was found to be pH 7, and the phage isolates are tolerant of alkalinity and sensitive to acidity.