Bradysia difformis is one of the most damaging pests in mushroom production in China. In this study, eight Bacillus thuringiensis strains were analyzed for insecticidal activity in B. difformis. The strain JW-1 showed the highest insecticidal activity against B. difformis larvae, but did not inhibit the mycelial growth of Pleurotus ostreatus and P. geesteranus. The 16S rRNA gene (1397 bp) and cyt2 gene (792 bp) were obtained from strain JW-1. The phylogenetic tree based on 16S rRNA gene and Cyt2 toxin showed that strain JW-1 was a member of B. thuringiensis and Cyt2 toxin belonged to Cyt2Ba toxin cluster. The Cyt2Ba toxin from strain JW-1 was overexpressed in E. coli as a fusion protein and the fusion protein (70 kDa) was purified by Ni-IDA affinity chromatography. The purified Cyt2Ba fusion protein was toxic to B. difformis larvae (LC50 was 2.25 ng/mL). The identification of Cyt2Ba from strain JW-1 and confirmation of the insecticidal activity of Cyt2Ba in B. difformis provided a new means of biological control of the important pest in mushroom production.

中文翻译：

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一株苏云金芽孢杆菌新菌株Cyt2Ba的鉴定及其对异形布拉迪菌的毒性

香菇是我国食用菌生产中危害最大的害虫之一。在这项研究中，分析了八株苏云金芽孢杆菌在 B. difformis 中的杀虫活性。菌株 JW-1 对 B. difformis 幼虫表现出最高的杀虫活性，但不抑制 Pleurotus ostreatus 和 P. geesteranus 的菌丝生长。16S rRNA 基因 (1397 bp) 和 cyt2 基因 (792 bp) 来自菌株 JW-1。基于16S rRNA基因和Cyt2毒素的系统发育树表明菌株JW-1属于苏云金芽孢杆菌，Cyt2毒素属于Cyt2Ba毒素簇。来自菌株 JW-1 的 Cyt2Ba 毒素在大肠杆菌中作为融合蛋白过表达，融合蛋白 (70 kDa) 通过 Ni-IDA 亲和层析纯化。纯化的 Cyt2Ba 融合蛋白对 B. difformis 幼虫有毒（LC50 为 2. 25 纳克/毫升）。菌株JW-1中Cyt2Ba的鉴定和Cyt2Ba对B. difformis的杀虫活性的确认为蘑菇生产中重要害虫的生物防治提供了新的手段。