Isolation and Characterization of Soil-Borne Lytic Bacteriophages Infecting Enterobacter spp. Causing Fire Blight like Disease on Apple in Egypt

Three phages showed lytic activity against Enterobacter cloacae subsp. dissolvens were
isolated from the soil surrounding diseased apple trees with fire blight like disease by
enrichment method. Selected phages purified by successive single plaque isolation technique.
On the basis of morphotypes the isolated phages were identified as members of the
Siphoviridae and Podoviride families. The phages exhibit different lytic activity against some
genera of Enterobacteriaceae. Phages kept infectivity at temperatures 5–75°C with optimum
temperature at 35°C. About 30 to 50 % of phage particles survived after treatment at 55ᴼC and
phages were deactivated after 85°C. The three phages survived through pH range of 4 to 12
with ability to tolerant sodium chloride conc. up to 10M. The optimum multiplicity of infection
(MOI) was (0.1) for all phages. In in Vitro activity assay in liquid culture, the three phages
achieved a peak reduction against their respective host compared to phage-free control. The
stability of phages at high temperature and wide range of pH, also the high lytic activity results
obtained against their host make them suitable for phage biocontrol application of fire blight
like disease in further study.