Identification and Analysis of Toxins in Novel Bacillus thuringiensis Strain Bt S3076-1 against Spodoptera frugiperda and Helicoverpa armigera

Despite the successful application of toxins from Bacillus thuringiensis as biological control agents against pests, new toxins having higher toxicity and broad-spectrum activity to insects are identified more and more. To find new toxins, in this study, based on the whole genome sequence of novel Bacillus thuringiensis strain Bt S3076-1, ten predicted toxic genes were identified, including six cry genes, two tpp genes, one cyt gene and one vip gene, among which six were novel toxins. Subsequently, SDS-PAGE analysis showed that the major proteins at spore maturation stage were about 120 kDa, 70 kDa, 67 kDa, 60 kDa and 40 kDa, while approximately 70 kDa and 40 kDa active proteins after trypsin digestion with the LC50 of 149.64 µg/g and 441.47 µg/g against Spodoptera frugiperda and Helicoverpa armigera larvae, respectively. Furthermore, pathological observation results showed the peritrophic membrane of Spodoptera frugiperda and Helicoverpa armigera larvae was degraded. These findings will provide experimental reference for further research on insecticidal activity, toxicity spectrum as well as the synergism of these toxins in Bt S3076-1.