Abstract: The protein components of the delta-endotoxin crystals from Bacillus thuringiensis HD-I (toxic to Lepidoptera), 3370-1 (nontoxic) and Tm13-14 (toxic to Lepidoptera, Diptera, and Coleoptera) were compared under the different lysated condition by SDS-PAGE. The results showed that Tm13-14 crystal contains two major peptides with MW 138 Kd, 132 Kd and a minor peptides of 65 Kd. The components of Tm13-14 crystal protein or its proteinase resistant peptides (PRPs) by gut juice of the three insect species tested are different from those of strain HD-1 and 3370-1. The toxic PRPs of Tm13-14, resulted from dissolving crystal by gut juice of three insect species, were purified by two steps, first by sephadex G-100 and thenby DEAE-52 chromatography. The results of bioassay and SDS-PAGE analysis suggested that the toxic PRPs to the larvae of Bornbyx mori were 68.5 and 59 Kd, to the larvae of Spodoptera litura were 71 Kd, 65 Kd and 59.6 Kd, to the larvae of Epilachna niponica were 69kD and 65 Kd. The LC50 values of intact crystal, the first purified toxic PRPs and 2nd purified toxic PRPs of Tm13-14 to the second instar larvae of E. niponica were 9.4, 4.1 and 3.2μg/ml respectively.

Key words: Becillus thuringiensis Tm13-14, parasporal crystal, toxic polyptide