Bacillus thuringiensis BT-1, BT-2가 생산하는 δ-endotoxin의 특성 규명

Abstract

Bacillus thuringiensis is a well-known species of entomophathogenic bacteria that is widely used as a biopesticide against many insect pests. It produces parasporal crystals (δ-endotoxin) and endospores during sporulation. In this report, the δ-endotoxin produced by Bacillus thuringiensis BT-1 and BT-2 were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), SDS-PAGE, and solubilization activity by alkaline solution. BT-1, BT-2 were cultured in the GBY medium, and the δ-endotoxin of them was purified with discontinuous sucrose density gradient centrifugation. Their δ-endotoxin was observed by SEM and TEM. Morphologically, the δ-endotoxin of BT-1 was a square and flat type, whose size was 1.73 ㎛ × 0.7 ㎛, and the δ-endotoxin of the BT-2 was spherical form whose size was 1.1 ㎛ × 0.9 ㎛ determined by SEM and TEM. The δ-endotoxin of the BT-1 was composed of 28 kDa and 21 kDa, however, it of the BT-2 was composed of 50 kDa, 35 kDa, and 22 kDa bands determined by SDS-PAGE. The purified crystals of BT-1 and BT-2 were dissolved gradually in alkaline solution as time goes by, and it was perfectly dissolved after 3 hours. It is supposed that the δ-endotoxin of crystal was converted to a state of activation in the course of time in the intestines of insect.