Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, United Kingdom.
Department of Engineering Science, University of Oxford, Parks Road, Oxford, OX1 3PJ, United Kingdom.
Water Res. 2019 Apr 15;153:295-303. doi: 10.1016/j.watres.2019.01.009. Epub 2019 Jan 21.
Bioremediation is a sustainable and cost-effective means of contaminant detoxification. Although Cr(VI) is toxic at high concentrations, various microbes can utilise it as an electron accepter in the bioremediation process, and reduce it to the less toxic form Cr(III). During remediation, it is important to monitor the level of toxicity and effectiveness of Cr(VI) reduction in order to optimize the conditions. This study employed a whole-cell bioreporter Acinetobacter baylyi ADPWH-recA to access the degree of toxicity of different species of Cr over a range of initial concentrations. It also investigated whether Cr isotope fractionation factors were impacted by different levels of Cr toxicity (related to its concentration) and Cr(VI) reduction rates by Cr resistant bacteria Pseudomonas fluorescens LB 300. The results show that, of both CrO and CrO, the whole-cell bioreporter was efficient in indicating the level of genotoxicity of Cr(VI) at low concentrations and cytotoxicity at high concentrations via variations of bioluminescence. High concentrations (> 100 mg/L) of Cr(III) could also strongly induce the luminescence in the bioreporter, indicating DNA damage at such abundance. Pseudomonas fluorescens LB 300 was found to be effective in reducing Cr(VI) even when the concentration was high (40 mg/L); however, complete Cr(VI) reduction was only observed at low concentrations (< 5 mg/L), since the toxicity of high concentrations of Cr(VI) impacted the effectiveness of reduction by the bacteria. During reduction, the C53r/C52r ratio of remaining Cr(VI) increased from its initial value, and the calculated fractionation factor by bacterial Cr(VI) reduction (ε) was -3.1±0.3‰. The fractionation factor was independent of the initial Cr(VI) concentration. Therefore, a single Cr isotope fractionation factor can be effectively applied in indicating the extent of bioremediation processing of Cr(VI) over a wide range of concentrations. This significantly simplified monitoring of Cr(VI) depletion in bioremediation, since variations of ε normally indicate a change in the reduction mechanism and therefore would complicate the elucidation of processes driving the remediation.
生物修复是一种可持续且具有成本效益的污染物解毒方法。虽然高浓度的 Cr(VI) 具有毒性，但各种微生物可以将其用作生物修复过程中的电子受体，并将其还原为毒性较低的 Cr(III) 形式。在修复过程中，监测 Cr(VI) 的毒性水平和还原效果非常重要，以便优化条件。本研究采用全细胞生物报告菌 Acinetobacter baylyi ADPWH-recA 来评估不同种类的 Cr 在一系列初始浓度下的毒性程度。还研究了 Cr 抗性细菌荧光假单胞菌 LB 300 对不同水平的 Cr 毒性（与其浓度有关）和 Cr(VI) 还原率是否会影响 Cr 同位素分馏因子。结果表明，对于 CrO 和 CrO，全细胞生物报告菌通过生物发光的变化，在低浓度下有效指示 Cr(VI) 的遗传毒性水平，在高浓度下指示细胞毒性。高浓度 (>100mg/L) 的 Cr(III) 也能强烈诱导生物报告菌发光，表明如此高浓度下的 DNA 损伤。荧光假单胞菌 LB 300 即使在高浓度（40mg/L）时也能有效还原 Cr(VI)；然而，只有在低浓度（<5mg/L）时才观察到完全还原 Cr(VI)，因为高浓度 Cr(VI) 的毒性会影响细菌还原的效果。在还原过程中，剩余 Cr(VI) 的 C53r/C52r 比值从初始值增加，并且通过细菌 Cr(VI) 还原计算的分馏因子（ε）为-3.1±0.3‰。分馏因子与初始 Cr(VI) 浓度无关。因此，单一的 Cr 同位素分馏因子可有效应用于指示 Cr(VI) 在较宽浓度范围内的生物修复处理程度。这极大地简化了 Cr(VI) 耗尽的生物修复监测，因为 ε 的变化通常表明还原机制发生了变化，因此会使阐明驱动修复的过程复杂化。
