Effects of Protoplast Fusion on d-endotoxin Production in Bacillus thuringiensis Spp. (H14)

In this study, mutant forms of Bacillus thuringiensis spp. israelensis (H14) were produced. Thesemutants were identified when the cells were cultured on chloramphenicol plates and stained withcrystal violet. Protoplasts of the mutants were isolated by enzymatic digestion (lysozyme) of the cellwalls at the presence of an osmotic stabilizer. The protoplasts were induced to fuse to each other in thepresence 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-serumagainst pure toxin was raised in rabbit and was used in single radial immunodiffusion. Thecomparison of δ-endotoxin concentration between B. thuringiensis fusion and the wild type strainsshowed that B. thuringiensis fusion has 1.48 time more toxin than wild type.