Department of Food, Environmental and Nutritional Sciences (DeFENS), University of Milan, Via Celoria 2, 20133 Milan, Italy.
Department of Science and High Technology (DiSAT), University of Insubria, Via Valleggio 9, Como, Italy.
Sci Total Environ. 2017 Jan 1;575:1395-1406. doi: 10.1016/j.scitotenv.2016.09.218. Epub 2016 Oct 5.
Polychlorinated biphenyls (PCBs) are toxic chemicals, recalcitrant to degradation, bioaccumulative and persistent in the environment, causing adverse effects on ecosystems and human health. For this reason, the remediation of PCB-contaminated soils is a primary issue to be addressed. Phytoremediation represents a promising tool for in situ soil remediation, since the available physico-chemical technologies have strong environmental and economic impacts. Plants can extract and metabolize several xenobiotics present in the soil, but their ability to uptake and mineralize PCBs is limited due to the recalcitrance and low bioavailability of these molecules that in turn impedes an efficient remediation of PCB-contaminated soils. Besides plant degradation ability, rhizoremediation takes into account the capability of soil microbes to uptake, attack and degrade pollutants, so it can be seen as the most suitable strategy to clean-up PCB-contaminated soils. Microbes are in fact the key players of PCB degradation, performed under both aerobic and anaerobic conditions. In the rhizosphere, microbes and plants positively interact. Microorganisms can promote plant growth under stressed conditions typical of polluted soils. Moreover, in this specific niche, root exudates play a pivotal role by promoting the biphenyl catabolic pathway, responsible for microbial oxidative PCB metabolism, and by improving the overall PCB degradation performance. Besides rhizospheric microbial community, also the endophytic bacteria are involved in pollutant degradation and represent a reservoir of microbial resources to be exploited for bioremediation purposes. Here, focusing on plant-microbe beneficial interactions, we propose a review of the available results on PCB removal from soil obtained combining different plant and microbial species, mainly under simplified conditions like greenhouse experiments. Furthermore, we discuss the potentiality of "omics" approaches to identify PCB-degrading microbes, an aspect of paramount importance to design rhizoremediation strategies working efficiently under different environmental conditions, pointing out the urgency to expand research investigations to field scale.
多氯联苯（PCBs）是有毒化学物质，难以降解，在环境中具有生物蓄积性和持久性，对生态系统和人类健康造成不利影响。因此，修复 PCB 污染土壤是首要解决的问题。植物修复是一种很有前途的原位土壤修复工具，因为现有的物理化学技术对环境和经济有很大的影响。植物可以提取和代谢土壤中存在的几种异生物质，但由于这些分子的顽固性和低生物利用度，它们吸收和矿化 PCB 的能力有限，这反过来又阻碍了对 PCB 污染土壤的有效修复。除了植物降解能力外，根际修复还考虑了土壤微生物吸收、攻击和降解污染物的能力，因此可以将其视为清洁 PCB 污染土壤的最适宜策略。微生物实际上是 PCB 降解的关键参与者，可以在有氧和无氧条件下进行。在根际中，微生物和植物相互促进。微生物可以在典型的污染土壤受胁迫条件下促进植物生长。此外，在这个特定的小生境中，根分泌物通过促进联苯分解途径发挥关键作用，该途径负责微生物氧化 PCB 代谢，并提高整体 PCB 降解性能。除了根际微生物群落外，内生细菌也参与污染物的降解，是用于生物修复目的的微生物资源的储备库。在这里，我们重点关注植物-微生物的有益相互作用，综述了在温室实验等简化条件下，结合不同植物和微生物物种从土壤中去除 PCB 的现有结果。此外，我们还讨论了“组学”方法在识别 PCB 降解微生物方面的潜力，这对于设计在不同环境条件下有效工作的根际修复策略至关重要，指出需要将研究调查扩展到野外规模。
