Identification of thecrygene inBacillus thuringiensisstrain WZ-9 and its toxicity againstHenosepilachna vigintioctomaculata

Abstract

AbstractBacillus thuringiensisstrain WZ-9, isolated from soil in Hebei province, China, was effective againstHenosepilachna vigintioctomaculatalarvae. The strain presented bipyramidal crystals with a protein band of 130 kDa in SDS–PAGE. The pH changes of the culture media showed important fluctuations during the 24 h growth cycle. The pH varied less in log and stationary phases than it did in the exponential phase. Bioassay results showed that the WZ-9 strain was only harmful to larvae ofH. vigintioctomaculataand not to either adults ofH. vigintioctomaculataor other several lepidopteran and coleopteran insects. LC50to second-instar larvae ofH. vigintioctomaculatawas 2.95×107cells/ml after 72 h. Genotypic investigations showed that this strain possessed thecry7gene. Sequence analysis demonstrated that the encoding gene contained an open reading frame (ORF) of 3414 bp and encoded 1138 amino acid residues. The deduced amino acid sequence was 99.65% identical to that of the reported Cry7Ab2 sequences. This gene was designated by the Bt δ-endotoxin nomenclature committee as Cry7Ab3 with accession number BI 1015188 in the GenBank database.