将高毒性的Cr(VI)还原成低毒的Cr(III), 是处理含Cr(VI)废水常用的方法之一。以高效还原Cr(VI)的苏云金芽胞杆菌(Bacillus thuringiensis, 简称Bt)407为研究对象, 将转座子随机突变载体pIC333转化Bt 407, 构建容量为1 500株的随机突变体库, 从中筛选出Cr(VI)还原能力极显著差异(P< 0.01)的突变株14株。通过扩增并测定转座子插入位点的侧翼序列, 确定Bt 407-Cr244突变株的转座子插入位点为细胞色素氧化酶亚单位Ⅰ。Bt 407及其14株突变株的生长曲线十分相近, 表明突变株Cr(VI)还原能力发生改变不是由菌株繁殖能力提高引起的。在培养24 h后, Bt 407-Cr149和Bt 407-Cr285培养液中的总络浓度比Bt 407极显著降低(P<0.01), 说明这2株突变株在解毒Cr(VI)过程中除了还原作用, 可能还具有生物吸附, 而其余12株突变子主要通过还原Cr(VI)起作用。

Reduction of Cr(VI) to Cr(III) was a potential useful process for remediation of Cr(VI)-affected environments. Bacillus thuringiensis (Bt) 407, which can efficiently reduce Cr(VI), was transformed with a transposon vector pIC333 and a library of 1 500 random insertion mutants was generated. 14 mutants, which Cr(VI)-reducing capacity were remarkably different (P<0.01) from that of Bt 407, were obtained. The flanking sequence of transposon insertion in Bt 407-Cr244 was sequenced to be cytochrome oxidase subunit I (COI) gene. The growth curves of Bt 407 and its 14 mutants were similar, indicating that the change of Cr(VI) reduction capacities of the mutants was not due to the strain populations. The fact that the total Cr of Bt 407 mutants Bt 407-Cr152 and Bt 407-Cr285 were remarkably different (P<0.01) from that of Bt 407 suggested that Bt 407 and its 12 mutants removed Cr(VI) by reduction, but Bt 407-Cr152 and Bt 407-Cr 285 might have additional biosorption abilities.