ISOLATION AND CHARACTERIZATION OF MUTANTS OF BACILLUS-THURINGIENSIS VAR ISRAELENSIS

Several mutants of Bacillus thuringiensis var. israelensis HD-500 (Bti ) were obtained after treatment with N-methyl-n'-nitro-N-nitrosoguanid ine. On the basis of the production (+) or absence (-) of spore (Spo) and crystal (Cry) the strains were grouped into three categories: Spo + Cry +, Spo + Cry - and Spo - Cry + .NGI-22, a Spo + Cry - mutant lac ked all crystal proteins. Both NGI-23 and NGI-23-1 were Spo - Cry + . NGI-23-1, however, produced multiple crystals per cell. These mutants could prove useful not only for analysing sporulation and crystal form ation as well as the linkage between the two genetic processes but als o for improving the potential of Bti as a microbial insecticide.