الفهرس 
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Abstract
The present study started with the isolation of seventy one local
bacterial strains on NA medium from dead snails and evaluation of their ability to produce molluscicidal toxins using bioassays against
Biomphalaria alaxandrina snails. Out of these strains, there were only three highly toxic strains (25, 30 and 45) caused 100% mortality after both exposure and recovery periods (4 days). Other highly toxic isolated strains had approximately the same toxicity as standard B. thuringiensis strain - 977 (caused 80% mortality for snails after 4 days). The remaining strains had low or no toxicity against snails. - Phenotypic characterization, specific primer polymerase chair reaction (PCR) and restriction fragment length polymorphism (R.FLP analysis for 16S rRNA gene have been used for characterization and identification of some toxic isolates. isolated strain 66 was selected foi sequencing of its 16S rRNA gene, analyzing its toxin protein by SDS-PA(E and for biochemical identification.