苏云金芽胞杆菌HD-73菌株sigL基因突变体的特性分析

Characteristics of sigL mutant in Bacillus thuringiensis HD-73

摘要:

【目的】通过分析苏云金芽胞杆菌sigL基因突变体的特征，进一步明确sigL基因在苏云金芽胞杆菌中的功能。【方法】测定了苏云金芽胞杆菌HD-73菌株，sigL基因缺失突变菌株和互补菌株在不同营养成分的培养基中的生长曲线以及在不同氮源条件下的生长情况。分别将调控aco操纵子（编码3-羟基丁酮脱氢酶系统）的转录调节基因acoR和调控bkd操纵子（编码催化支链脂肪酸合成的酶系统）的转录调节基因bkdR的启动子与lacZ基因融合，并转入出发菌株和sigL突变体中，测定b-半乳糖苷酶的活性。【结果】sigL突变体不能利用精氨酸、脯氨酸、缬氨酸、异亮氨酸、谷氨酰胺、苯丙氨酸、蛋氨酸、色氨酸为唯一的氮源；b-半乳糖苷酶的活性分析表明：在sigL突变体中acoR基因和bkdR基因的启动子活性降低。序列比对分析表明：Bt中的AcoR和BkdR的蛋白结构域与依赖于sL的转录调节因子的保守序列相似。【结论】苏云金芽胞杆菌中sigL基因的缺失可能阻碍了某些重要碳、氮源参与的代谢途径。在Bt中AcoR和BkdR是依赖于sL的转录调节因子。

Abstract:

[Objective] The purpose of this study was to characterize sigL mutant in Bacillus thuringiensis (Bt) HD-73, and to determine the function of sigL gene of Bt. [Methods] We studied the growth speed of the sigL mutant and complementary strain in different nutrient medium with different amino acids as nitrogen source respectively. lacZ gene was fused with the promoter of the acoR gene and bkdR gene, and two recombined genes were expressed in sigL mutant strain and HD-73 wild strain sequentially. [Results] sigL mutant could not grow on arginine, proline, valine, isoleucine, glutamine, phenylalanine, methionine and tryptophane as the sole nitrogen source separately. Activity of β-galactosidase in sigL mu-tant strain was much lower than it in wild-type strain and sequence analysis showed that the domain of AcoR and BkdR are similar to the conserved domain of SigL-dependent transcriptional activator in Bt. [Conclusion] The deletion of sigL gene maybe blocked some important metabolic pathways. AcoR and BkdR are σL-dependent transcriptional activators in Bacillus thuringiensis strains, probably the operons which were regulated by AcoR and BkdR were also controlled by σL respectively.