δ-Endotoxin of Bacillus thuringiensis var. israelensis

Abstract

The alkaline-dissolved Bacillus thuringiensis israelensis (BTI) δ-endotoxin when introduced by injection was biologically active against a wide spectrum of host animals including insects from four orders and mice. The LD50 for dissolved BTI δ-endotoxin in mice was 1.31 PPM and in Trichoplusia ni (Lepidoptera: Noctuidae) 3.71 PPM. Neuromuscular effects like heart cessation, lost coordination, tremor, and paralysis were observed in test animals. Using the appearance of lactate dehydrogenase in insect hemolymph post-injection as a cytosolic marker, we found that dissolved BTI δ-endotoxin was cytotoxic. In vivo recordings of activity in the ventral nerve cord post-injection indicated that dissolved BTI δ-endotoxin at the T. ni LD50 elicited hyperexcitability and then nerve death as was also the case for the organophosphate, methamidophos. The cytotoxin phospholipase-A2 when injected at its LD50 elicited no neural response. BTI poisoning was also temperature dependent while BTI cytotoxicity was not. Proteins at 24, 27, 35, 49 and 68K daltons were resolved from the dissolved BTI δ-endotoxin. These were introduced in various combinations by injection and ingestion into mice and insects and compared to the alkaline-dissolved Bacillus thuringiensis kurstaki β-endotoxin.