Enterobacter Strain IPPBiotE33 Displays a Synergistic Effect with Bacillus thuringiensis Bt185

The discovery and isolation of new non-Bt insecticidal bacteria and genes are significant for the development of new biopesticides against coleopteran pests. In this study, we evaluated the insecticidal activity of non-Bt insecticidal bacteria, PPBiotE33, IPPBiotC41, IPPBiotA42 and IPPBiotC43, isolated from the peanut rhizosphere. All these strains showed insecticidal activity against first- and third-instar larvae of , and . IPPBiotE33 showed the highest toxicity among the four strains and exhibited virulence against . The genome of IPPBiotE33 was sequenced, and a new protein, 03673, with growth inhibition effects on was obtained. In addition, IPPBiotE33 had a synergistic effect with Bt185 against in bioassays and back-inoculation experiments with peanut seedlings. IPPBiotE33 induced a decrease in hemocytes and an increase in phenol oxidase activity in hemolymph, known as the immunosuppressive effect, which mediated synergistic activity with Bt185. This study increased our knowledge of the new insecticidal strain IPPBiotE33 and shed new light on the research on new insecticidal coaction mechanisms and new blended pesticides.