Non-toxic isolates of Bacillus thuringiensis producing parasporal inclusions with unusual protein components

Two strains of Bacillus thuringiensis isolated in Japan, designated 84‐F‐58‐20 and 84–F–58–35, produced unique parasporal inclusions (PI) non‐toxic to four insect species of three orders. Microscopic observation showed that the PI were rhombic but flat in shape. Intact PI of these isolates contained the major protein of 60 kD and several minor proteins. Upon dissolution of these PI with alkali (pH 10.2) con‐taining silkworm (Bombyx mori) larval gut juice, the 60 kD major protein was degraded and several proteins with lower molecular masses were detected in the supernatant fluid. Of these, the 27 kD protein was predominant.