粗犷的电子垃圾拆解活动导致大量的持久性有机污染物，如：多氯联苯（PCBs）和多溴联苯醚（PBDEs）释放到土壤中，对生态环境与人体健康构成了严重威胁。微生物降解是土壤中PCBs消减的重要途径。但在实际应用中，PCBs的微生物修复却受到了极大限制，究其原因主要有：一、通过分离培养获得的微生物菌种有限，应用时可选项不多；二、电子垃圾拆解区土壤中同时含有高浓度的多种重金属，这对微生物的金属抗性提出了更高要求；三、对原位环境下功能微生物及其降解机制缺乏认识，难以制定有效的调控手段；四、实际环境中的功能微生物与其功能基因无法联系起来，限制了对高效的功能基因异源表达宿主的挖掘，阻碍了功能基因的资源化利用。

近期，中国科学院广州地球化学研究所博士后江龙飞和合作导师罗春玲，利用DNA稳定性同位素探针技术（DNA-SIP），不经分离培养，对清远电子垃圾污染土壤中的PCBs降解微生物进行了原位研究。鉴定得到了包括Ralstonia，Cupriavidus和DA101在内的21种功能微生物，并首次报道了不可培养细菌DA101具有降解PCBs的能力。研究获得了1个13.8 kb的PCBs降解操纵子，通过解析操纵子结构，揭示了PCBs的降解机制（图1）和该操纵子的水平转移能力。基于四核苷酸指纹特征分析，成功地将功能基因与功能微生物联系了起来，证明了操纵子来自于Ralstonia（图2）。该研究在鉴定功能微生物的同时，揭示了PCBs微生物降解机制，并为功能基因起源分析提供了新途径。该研究成果不仅深化了PCBs污染土壤微生物修复的理论基础，为功能微生物的探查和功能基因的资源化利用亦提供了新思路。

该研究得到国家自然科学基金、广州市科技计划项目的资助，相关成果已发表于Environmental Science & Technology。(来源：中国科学院广州地球化学研究所）

Biphenyl-Metabolizing Microbial Community and a Functional Operon Revealed in E-Waste-Contaminated Soil

Abstract  Primitive electronic waste (e-waste) recycling activities release massive amounts of persistent organic pollutants (POPs) and heavy metals into surrounding soils, posing a major threat to the ecosystem and human health. Microbes capable of metabolizing POPs play important roles in POPs remediation in soils, but their phylotypes and functions remain unclear. Polychlorinated biphenyls (PCBs), one of the main pollutants in e-waste contaminated soils, have drawn increasing attention due to their high persistence, toxicity, and bioaccumulation. In the present study, we employed the culture-independent method of DNA stable-isotope probing to identify active biphenyl and PCB degraders in e-waste-contaminated soil. A total of 19 rare operational taxonomic units and three dominant bacterial genera (Ralstonia, Cupriavidus, and uncultured bacterium DA101) were enriched in the 13C heavy DNA fraction, confirming their functions in PCBs metabolism. Additionally, a 13.8 kb bph operon was amplified, containing a bphA gene labeled by 13C that was concentrated in the heavy DNA fraction. The tetranucleotide signature characteristics of the bph operon suggest that it originated from Ralstonia. The bph operon may be shared by horizontal gene transfer because it contains a transposon gene and is found in various bacterial species. This study gives us a deeper understanding of PCB-degrading mechanisms and provides a potential resource for the bioremediation of PCBs-contaminated soils.

原文链接：https://pubs.acs.org/doi/pdf/10.1021/acs.est.7b06647