الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Bacillus thuringiensis (Bt) which is widely used as a biological insecticide is highly sensitive to lysis by bacteriophages and consequently its commercial fermentation suffers mainly from bacteriophage infection which in-turn leads to great economic losses and make it less desirable in manufacturing process. This is a humble effort to make mutant(s) with increased resistance to bacteriophages This was achieved by applying UV mutational wave lengths of 254, 260, 280, and 315 nm to the Bt wild type strain. A resistant mutant (R) was obtained. It was found that the resistant mutant produces only spores and no crystals. Conjugation between Bt wild-type (S) and Bt mutant (R) was done to restore crystal production. A11 was the selected one of the resulted transconjugants. It was confirmed to be phage resistant by sensitivity assays and to be a crystal producer by both endospore stain and the most confirmatory evidence, PCR. A11 was found to be best fit of our concern