中文摘要：

测定苏云金芽胞杆菌（Bacillus thuringiensis,简称Bt）407及其突变株407ΔplcR、407ΔinhA2、407ΔmpbE、407ΔsigmaE和407ΔsigmaK对数生长期与稳定期的拐点时间t0,测定不同时间点发酵液上清中的总铬（Cr）和Cr（Ⅵ）的浓度,并分析Bt 407基因组的抗性相关基因,进而初步构建Bt解毒Cr（Ⅵ）模式图.结果表明,plcR、inhA2、mpbE、sigmaK负调控Bt 407解毒Cr（Ⅵ）的能力并主要影响Cr（Ⅵ）还原过程,sigmaE不影响对Cr（Ⅵ）的解毒过程.利用Bt 407基因组序列分析得到与Cr（Ⅵ）抗性相关基因NADPH偶氮还原酶基因azoR、外排蛋白基因efx和chrA.推测Bt 407对Cr（Ⅵ）抗性机制可能为：azoR编码NADPH偶氮还原酶将细胞内Cr（Ⅵ）还原为Cr（Ⅲ）,Cr（Ⅲ）再通过ChrA或与azoR共表达的外排蛋白Efx从细胞质中排出,这一还原过程直接/间接受到plcR、inhA2、mpbE、sigmaK等调控基因的负调控.因此,Bt 407对Cr（Ⅵ）的解毒机制是由azoR、efx、chrA等主效基因与plcR、inhA2、mpbE、sigmaK等调控基因共同作用的复杂网络.

英文摘要：

This study aimed to investigate the effects of insecticidal regulatory genes on Cr（Ⅵ） detoxification of Bacillus thuringiensis 407. The growth curve of Bt 407 and its mutants（407 ΔplcR, 407 ΔinhA2, 407 ΔmpbE, 407 ΔsigmaE and 407 ΔsigmaK） were applied to determine the t0（time of the strain enter into the stationary phase）. The Cr（VI） and total Cr concentrations at t-3（3 h before t0）, t-2（2 h before t0）, t-1（1 h before t0）, t0, t1（1 h after t0）, t2（2 h after t0）, t3（3 h after t0） and t4（4 h after t0） were also detected. The genomic sequence of Bt 407 was analyzed for the existence of Cr（Ⅵ） resistant genes. And the model chart of Bt 407 Cr（Ⅵ） detoxification was primarily constructed. The results showed that PlcR, InhA2, MpbE and SigmaK negatively regulated the detoxification of Cr（Ⅵ） by reducation, while SigmaE had no effects on the process. Cr（Ⅵ） resistant genes azoR, efx and chrA were obtained by genomic analysis of Bt 407. The mechanisms of Cr（Ⅵ） detoxification by Bt 407 was proposed as follows： AzoR reduces Cr（Ⅵ） to Cr（Ⅲ）, which is negatively regulated by PlcR, InhA2, MpbE and SigmaK. The efflux of chromium was conferred by antiporters Efx and ChrA. These results suggested that the resistance of Bt 407 to Cr（Ⅵ） is a complicated network regulated by azoR, efx, chrA, plcR, inhA2, mpbE and sigmaK genes.