RESUMEN
In this study, mutant forms of Bacillus thuringiensis spp. israelensis [H14] were produced. These mutants were identified when the cells were cultured on chloramphenicol plates and stained with crystal violet. Protoplasts of the mutants were isolated by enzymatic digestion [lysozyme] of the cell walls at the presence of an osmotic stabilizer. The protoplasts were induced to fuse to each other in the presence of PEG 6000. The frequency of regeneration and recombination was 80% and 2 10-4, respectively. In order to survey the effect of protoplast fusion on production of toxin, anti-serum against pure toxin was raised in rabbit and was used in single radial immunodiffusion. The comparison of -endotoxin concentration between B. thuringiensis fusion and the wild type strains showed that B. thuringiensis fusion has 1.48 time more toxin than wild type