Abstract

Bacillus thuringiensis populations ranged between 4.23 x 10⁵, 6.52 x 10⁵ cfu/g soil and consist of 11 types of isolates with 3 polymorphic, 7 spherical and 1 bipyramidal type of crystals. Polymorphic crystal containing isolates were further characterized. B. thuringiensis isolates were circular, white, flat and undulate or entire. These were gram-positive. These tolerated 5% NaCl and failed to grow anaerobically. None of these were positive for indole production. All were sensitive to streptomycin, vancomycin, polymyxin B and norfloxacin but resistant to penicillin G and ampicillin/sulbactum. All of the isolates were crystal forming rods, width of rods was >0.9 um, catalase positive and sporangia were not swollen. All of the isolates hydrolyzed protein but only BTc 175 produced arginine dihydrolase, BTc 152 and BTc 175 produced urease.

Key words: Bacillus thuringiensis, soil, isolates, polymorphic crystal.