Genomic exploration of Bacillus thuringiensis strain T381: Revealing its genetic potential against lepidopteran pests

Bacillus thuringiensis (Bt) is a Gram-positive, spore-forming bacterium widely recognized for its entomopathogenic properties and used as a biopesticide due to its potent activity against insect and nematode pests. This study characterizes a native Bt isolate, T381, that exhibits strong insecticidal activity against lepidopteran pests. Scanning Electron Microscopy revealed the formation of bipyramidal, cuboidal, and spherical parasporal crystals, while SDS-PAGE profiling of the spore-crystal complex identified three major protein bands (∼135, ∼88, and ∼65 kDa) corresponding to Cry1, Vip3, and Cry2 toxins. PCR amplification confirmed the presence of cry and vip gene combinations. Toxicological assessment using probit analysis determined LC₅₀ values of 1.703, 14.500, 1.270, and 0.597 μg/mL against Spodoptera litura, S. frugiperda, Helicoverpa armigera, and Plutella xylostella, respectively. The draft genome of isolate T381 comprises 244 scaffolds totaling 6,424,996 base pairs, with an N50 of 93,189 bp. BLAST-based analysis identified 13 plasmids, and genome annotation revealed 6637 protein-coding genes, 57 tRNA genes, 5 rRNA genes, and 5 non-coding RNA genes. Eleven insecticidal toxins, such as Cry1Ac5(a), Cry1Aa18, Cry1Ac5(b), Cry1Aa6, Cry1Ia42, Cry2Aa9, Cry2Ab41, Vip3Aa86, Mpp46Ab1, Vpb4Ca1, and Spp1Aa1 were detected. Additional toxin-related genes such as Zwa5A, Zwa5B, Zwa6, ChitinaseC, InhA1, InhA2, Enhancin, and Bmp1 were also identified, highlighting the isolate's potential for broad-spectrum pest control.