Occurrence of iBacillus/ii /iithuringensis/i Bacteriophages in the Egyptian Arid Soil

摘要

In this study, two phages specific for Bacillus thuringiensis were isolated from arid soils. The phages were designated as Bt1 and Bt2. They were propagated by the liquid enrichment method and purified by the polyethylene glycol and dextran sulfate followed by high speed centrifugation, the morphology of purified particles was determined using transmission electron microscopy. Electron micrograph indicated that Bt1 phage has isometric particle, its head diameter is about 140 x165 nm and contractile tail type, about 117 nm length, while the particle of phage Bt2 has long contractile tail with 206 nm length and its head is isometric with diameter of about 140 x 124 nm, phages appeared to be a member of the Myoviridae family based on their structure and particle morphology. The isolated phages have narrow host range, which they able to infect Bacillus thuringiensis, Bacillus subtilis and Bacillus lechiniformis, Bt1 and Bt2 viral genomes were digested by EcoRI. The genome size was estimated to be ～4.06 kbp for Bt1 phage and ～6.43kbp for Bt2 phage. To our knowledge, this is the first report on the isolation of a bacteriophage specific for Bacillus thuringiensis from arid soil in Egypt.