All major insecticidal genes of Bacillus thuringiensis var. israelensis (Bti) are controlled by the sporulation-specific sigma factor Sigma E (sigE), while sigE is negatively regulated by Sigma K (sigK). Therefore, knocking out sigK plays an important role in regulating the expression of insecticidal genes in Bti. A sigK deletion mutant of B. thuringiensis var. israelensis strain Bt-59, Bt59(ΔsigK), was constructed by homologous recombination and characterized. The sigK deletion resulted in no mature spores and delayed mother cell lysis from T25 to T60, while the genetically complemented strain, Bt59(HFsigK), had mother cell lysis at T25. Compared to Bt-59, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that the expression of Cry4Aa2/4Ba1 and Cyt1Aa1 proteins in Bt59(ΔsigK) increased approximately 1.67 and 1.21 times, respectively. However, there was no significant change in Cry11Aa1 protein expression between the two strains. Bioassay results showed that the sigK deletion mutation slightly reduced the insecticidal activity of Bt-59 against Culex pipiens pallens and did not obviously affect activity against Aedes albopictus.

中文翻译：

---

苏云金芽孢杆菌 sigK 缺失突变体的特征。以色列 Bt-59 菌株

苏云金芽孢杆菌变种的所有主要杀虫基因。israelensis (Bti) 受孢子形成特异性西格玛因子 Sigma E (sigE) 控制，而 sigE 受西格玛 K (sigK) 负调控。因此，敲除sigK对调控Bti杀虫基因的表达具有重要作用。苏云金芽孢杆菌变种的 sigK 缺失突变体。israelensis 菌株 Bt-59，Bt59(ΔsigK)，通过同源重组构建并表征。sigK 缺失导致没有成熟的孢子和母细胞裂解从 T25 延迟到 T60，而遗传互补菌株 Bt59(HFsigK) 在 T25 具有母细胞裂解。与Bt-59相比，十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）分析表明Bt59（ΔsigK）中Cry4Aa2/4Ba1和Cyt1Aa1蛋白的表达增加了约1。分别为 67 倍和 1.21 倍。然而，两种菌株之间的 Cry11Aa1 蛋白表达没有显着变化。生物测定结果表明，sigK缺失突变略微降低了Bt-59对淡色库蚊的杀虫活性，对白纹伊蚊的活性没有明显影响。