ISOLATION AND CHARACTERIZATION OF RHIZOBIOPHAGES FOR RHIZOBIUM SPP. AND BRADYRHIZOBIUM SPP.

Document Type : Original Article

Authors

1 Department of Microbiology, Faculty of Agriculture, Cairo University, Giza, Egypt

2 Agricultural Microbiology Research Department, Soils, Water and Environment Research Institute, Agricultural Research Center, Giza, Egypt

Abstract

Rhizobium bac :eriophages in soils were examined by liquid enrich-nest culture. The survey included 80 soil samples representing various locations from the Nile Valley in Egypt. The phages detected in only 25% of the samples with phage titer ranged from 101 0 103 plageforming units (PF)) g-1 soil. Rigminosamm by. !Ilford ARC 102 yielded higher titer among sttrains tested being 8.2x103 PRI g-1 soil, while B j aponicum USDA 218 gave the lowest titer of rhizobiohages being 2.4 x 103 PFU g­1 sod. Eleven phages were isolated on the basis of phaquue inoijibulugy and four of them (J, 14, T, and V) were Fly charactterized. The four phages were found to have a wide host range on 16 rhizobial strains used the isolattion of phages. Beam microscopy revealed that phage J specific for 8.japonicum USDA 218 and phage T specific for R.kguminosarun bv. trfolii ARC 102 were tailless and had pentagonal head (Type 1). Length and width of the head were 82.4 and 88.2 nrn for phage J and 172.5 and 156.8 nm for phage , respectively. Phage 14 spe­cific for Rieguminosarum bv. viceaelCARDA 441 had an elongated head and noncontractde tail, the head diameter was 196.0 nm and the tail le­ngth was 176.5 nm (Type III). Molecular weightt of phages protein using gel elecrophoresis (SOS-PAGE rev ealed (three major and tthree minor bands for each phage isolate. The relaive rnobilitties of the major bands were SS, 34 and 19 Kd for all phages but the minor bands were 59, 30 and 25 Kd for phage J. Florescent microscopy for pilled phage nucleic acid showed that rhizobiciphages J, M, T and V contained deoxyribonu­cleic acid (DNA). Electtrophoresis agarose gel revealed that molecular weighs of phages DNA were 25..5, 24.5, 26.0 and 23.5 Kb for J. 14,7 and V phages. respecttively. Characterization of phage growth cycle by one-step growth experiments revealed that the latent period was ca. 75 min for phage al and 90 min. for phage J, and the average burst size was 100 PFU ce9-1 for he former and 120 PFU cell-1 for the latter.

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