Isolation and characterization of rhizobiophages specific for Rhizobium leguminosarum from some Egyptian soils

In the present study, forty soil samples representing several localities in Egypt were collected to: 1) Evaluate the distribution of rhizobiophages in Egyptian soils, 2) Isolate some phages specific for some species of Rhizobium, 3) Examine the morphology of the isolated phage particles, 4) Determine the molecular weight of both protein and nucleic acid of the obtained phages and differentiate between phage isolates by RAPD-PCR technique. The occurrence of rhizobiophages were always associated with legume plantation.The phages were detected only in 15 samples out of 40 rhizosphere samples with phage titre ranged from 10 to 103 PFU/ml. The tested strains (isolates) of Rhizobium showed variable sensitivity against the isolated phages. Generally the plaques of isolated phages differed in both morphology and size. The electron microscopic photographs of four isolated phages revealed that they all have icosahedral heads (hexagonal or pentagonal), and they have a relatively short tails. SDS-PAGE of the three phages Φ 6, Φ 7 and Φ 8 were done , and the similarity coefficient value between Φ 6 and Φ 7 was 0.75 RAPD PCR using two different arbitrary primers A2 and A4 were successfully applied in amplifying genomic DNA of the two phages Φ 6 and Φ 7. The similarity coefficient values between phages Φ 6 and Φ 7were estimated and found to be 0.62.