Comprehensive Genomic Insights and Insecticidal Evaluation of Bacillus thuringiensis Strain T419 against Lepidopteran...

Controlling agricultural insect pests primarily depends on chemical insecticides, which pose environmental and health risks. This study comprehensively characterizes Bacillus thuringiensis (Bt) strain T419 and explores its potential as an eco-friendly biopesticide. Morphological analysis revealed diverse crystal structures including bipyramidal, spherical, and cuboidal shapes, indicative of broad insecticidal activity. SDS-PAGE confirmed the presence of key proteins corresponding to Cry1 (~ 130 kDa), Cry2 (~ 65 kDa), and Vip3 (~ 88 kDa), known for their efficacy against lepidopteran pests. PCR screening confirmed the presence of genes encoding these insecticidal proteins, such as cry1, cry1Ac, cry1Ab, cry2, cry2Aa, cry2Ab, and vip3A. Whole genome sequencing yielded a 6.4 Mb draft genome with 6,962 protein-coding sequences, including 2,327 hypothetical proteins, suggesting significant potential for novel gene discovery. Notably, 14 plasmids were identified which likely harboring key insecticidal genes. Bioassays demonstrated T419's effectiveness against economically important lepidopteran pests such as Spodoptera frugiperda (LC₅₀ value of 2.821 µg/mL), Spodoptera litura (LC₅₀ value of 1.569 µg/mL), and Plutella xylostella (LC₅₀ value of 0.363 µg/mL). Genome annotation revealed Bt genome T419 possesses many insecticidal toxin proteins such as Cry1Aa18, Cry1Ab11, Cry1Ab14, Spp1Aa1, Mpp46Ab1, Cry1Ac5, Cry1Ia42, Cry2Aa9, Cry2Ab41, and Vip3Aa86. In addition, it also possesses various virulence factors, including InhA metalloproteases, phospholipase C, sphingomyelinase, and chitinase, elucidating T419's sophisticated pathogenic mechanisms. These findings suggest that the Bt strain T419 is a promising candidate for developing new biopesticide formulations, offering a potent combination of broad-spectrum insecticidal activity and genetic diversity.