Genome sequence analysis and insecticidal characterization of <em>Bacillus thuringiensis</em> Bt-UNVM_94, a strain showing dual insecticidal activity against lepidopteran and coleopteran pests.

Abstract

Bacillus thuringiensis (Bt) is a gram-positive and spore-forming bacterium that synthesizes a wide diversity of proteins with insecticidal activity and which has demonstrated its potential and safety as a biocontrol agent for more than four decades. However, several susceptible insect species have been reported for evolving resistance, which demands screening for strains exhibiting novel insecticidal properties. In this work, we performed the genome sequence analysis and insecticidal characterization of a Bt strain designated Bt-UNVM_94, isolated from Argentina. Its genomic sequence harbours one coding sequence showing homology to the crystal protein Cry7Ga1 plus two others showing similarity to Mpp2Aa3 (ETX/Mtx2) protein and a putative mosquitocidal protein (NPP1). Cry7A and Cry7B are known to be distinctively active against some coleopteran and lepidopteran larvae, respectively. Spore-crystal mixtures used for SDS-PAGE analysis showed a band corresponding to the predicted size of Cry7Ga-like protein (128 kDa). Bioassays performed also with spore-crystal mixtures exhibited dual toxicity with 50% and 91% mortality against Cydia pomonella (Lepidoptera: Tortricidae) and Anthonomus grandis (Coleoptera: Curculionidae), respectively, representing that we believe the first insecticidal activity report for a Cry7Ga-like protein. Screenings of novel Bt strains may provide proteins with novel insecticidal properties that can be used to suppress insect resistance to the most used Bt-crops in agriculture.