Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University, 410083 Changsha, China; Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, 410083 Changsha, China.
Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University, 410083 Changsha, China.
Ecotoxicol Environ Saf. 2018 Oct 30;162:139-146. doi: 10.1016/j.ecoenv.2018.06.090. Epub 2018 Jul 11.
Here, Pannonibacter phragmitetus BB was investigated at genomic, genetic and protein levels to explore molecular mechanisms of chromium biotransformation, respectively. The results of Miseq sequencing uncovered that a high-qualified bacterial genome draft was achieved with 5.07 Mb in length. Three novel genes involved in chromate reduce and transport, named nitR, chrA1 and chrA2, were identified by alignment, annotation and phylogenetic tree analyses, which encode a chromate reductase (NitR) and two chromate transporters (ChrA1 and ChrA2). Reverse transcription real-time polymerase chain reaction (RT-qPCR) analyses showed that the relative quantitative transcription of the three genes as the maximum reduction rate of Cr(VI) were significantly up-regulated with the increasing initial Cr(VI) concentrations. However, at the maximum cell growth points nitR was in a low transcription level, while the transcription of chrA1 and chrA2 were hold at a relatively high level and decreased with the increasing initial Cr(VI) concentrations. The ex-situ chromate reducing activity of NitR was revealed a V of 34.46 µmol/min/mg enzyme and K of 14.55 µmol/L, suggesting feasibility of the reaction with Cr(VI) as substrate. The multiple alignment demonstrates that NitR is potentially a nicotinamide adenine dinucleotide phosphate (NADPH) dependent flavin mononucleotide (FMN) reductase of Class I chromate reductases. Our results will prompt a large-scaled bioremediation on the contaminated soils and water by Pannonibacter phragmitetus BB, taking advantage of uncovering its molecular mechanisms of chromium biotransformation.
在这里，分别从基因组、遗传和蛋白质水平研究了 Pannonibacter phragmitetus BB，以探索铬生物转化的分子机制。Miseq 测序的结果揭示了一个高质量的细菌基因组草案，长度为 5.07Mb。通过比对、注释和系统发育树分析，鉴定了三个参与铬酸盐还原和转运的新基因，分别命名为 nitR、chrA1 和 chrA2，它们分别编码一个铬酸盐还原酶（NitR）和两个铬酸盐转运蛋白（ChrA1 和 ChrA2）。反转录实时聚合酶链反应（RT-qPCR）分析表明，随着 Cr(VI)初始浓度的增加，这三个基因的相对定量转录与 Cr(VI)的最大还原率呈显著上调。然而，在最大细胞生长点，nitR 的转录水平较低，而 chrA1 和 chrA2 的转录水平则保持在相对较高的水平，并随着 Cr(VI)初始浓度的增加而降低。NitR 的体外铬还原活性表明 V 为 34.46µmol/min/mg 酶，K 为 14.55µmol/L，表明以 Cr(VI)为底物的反应具有可行性。多重比对表明，NitR 可能是 I 类铬酸盐还原酶中依赖烟酰胺腺嘌呤二核苷酸磷酸（NADPH）的黄素单核苷酸（FMN）还原酶。我们的研究结果将促进利用 Pannonibacter phragmitetus BB 对受污染的土壤和水进行大规模生物修复，利用其揭示的铬生物转化的分子机制。
