الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Bacillus thuringiensis is highly sensitive to lysis by bacteriophages especially during commercial fermentation process which leads to great economic losses. In pursuit to improve the local industrial strain of Bt and make it resistant to bacteriophages several mutants were selected either directly or through conjugation between Bt wild-type and phage resistant mutants. Trans-conjugant strain (phage resistant and crystal producer) was thoroughly examined at bactriological and molecular levels in comparison to the wild type and mutant Bt strains. These included: endospore staining, analysis of protein banding patterns of vegetative and sporulated cells, phage sensitivity assay, phage adsorption and blocking phage adsorption at Bt cell surface by cell lystae of sonicated Bt fractions, as seen and photographed by electron microscope. Moreover, the genetic stability of the mutant strain and the trans- conjugant strain were confirmed by continual transfer for at least 20 generations and re-examine their properties. The localization of the gene encodes for the phage receptor in the three Bt strains was confirmed by curing experiment that proved its stable inheritance in the three strains. Moreover, the cell lystaes of these two strains were not able to protect the wild-type strain from being infected by the phage, suggesting no role for internal enzymes such as those of restriction and modification in preventing phage infection of the Bt strain cells. PCR technology was confirmed three Bt strains gave positive PCR product for the gene encoding for the phage receptor, only the Bt mutant strain 1 did not give a typical PCR product characteristic of the gene encodes for the ICP. The logic of the data led to the cloning and sequencing of the gene encodes for the phage receptor molecule from the wild-type strain 3 which were successfully done using the two specific DNA primers: P6 and P7. Analysis of the nucleotide sequence of the cloned gene (710 nucleotides = 231 amino acids). The amino acids sequence was analyzed for specific motifs using the PROSITE patterns (frequent match producers) postprocessing software which resulted in the presence of 3 possible site for protein phosphorylation, six site for myritylation and one site for protein kinase C phosphorylation. These sites for posttranscription modification of this protein are necessary to carryout its function in the cell. Also, the DAS server was used to predict the transmembrane regions of the current amino acid sequence which indicates the presence of two cutoffs on the plots: a ”strict” one at 2.2 DAS score, and a ”loose” one at 1.7. This confirms the cloned actually gene encodes for the phage receptor on the surface of the wild-type Bt strain and its involvement in the infection of the Bt cell.