Morphology and general characteristics of phages specific to Lens culinaris rhizobia

Four lytic phages, namely LRP-1, LRP-4, LRP-13, and LRP-15, active against indigenous rhizobial strains of Lens culinaris were isolated and characterized for their individual morphology, host range, plaque characteristics, lytic behavior, and restriction endonuclease profiling of phage DNA. All phages had a typical polyhedral head and long non-contractile tail, representing the bacteriophage family close to Siphoviridae. Phages produced distinct types of plaques on their indicator bacterial strains. The host range of the phage isolates was restricted to Rhizobium leguminosarum biovars and no cross infectivity among susceptible strains was observed. A study on the lytic cycle of the phages under identical conditions exhibited distinct latent period and burst size. Inactivation pattern of phages with temperature and UV light was quite distinct. Phage LRP-1 showed higher thermal resistance, though greater sensitivity to UV light, as compared to other phages. Genome sizes of the phages were estimated to vary between 50–72 kbp. The 16S rRNA sequence analysis of the phage indicator rhizobial strains revealed 81% to 100% similarity with R. leguminosarum bv. viciae. The phages could thus prove to be considerably useful in typing and investigating into the genetic variability which might exist amongst the soil rhizobia nodulating Lens culinaris.