Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes, Université Paul Verlaine Metz, CNRS UMR7146, IUT Thionville-Yutz, Impasse Alfred Kastler, 57970 Yutz, France.
Sci Total Environ. 2011 Sep 15;409(20):4489-95. doi: 10.1016/j.scitotenv.2011.06.049. Epub 2011 Jul 22.
Phytoremediation is considered as a promising and cost-effective method to enhance bioremediation of polluted soils. Exudation of plant root secondary metabolites similar to organic pollutants may induce the expression of microbial degradative enzymes and favour cometabolism of xenobiotics. We investigated the contribution of Miscanthus x giganteus root exudates in the biostimulation of PAH-degradation. This perennial grass was chosen because of its capability to grow on polluted soils and its high biomass production for non-food purposes. First, the impact of cometabolism phenomena was evaluated on the selective enrichment of pyrene-degrading bacterial consortia. The identification of each isolated strains following incubation with pyrene only, "pyrene+phenanthrene", "pyrene+salycilate" or "pyrene+diesel fuel" showed a varying bacterial diversity and pyrene-degrading ability, depending on the co-substrate used. Then, a microplate assay was designed, based on the simultaneous measurement of bacterial consortia growth and degradation activity, in the presence of PAH and total root exudates. Results showed that i) the addition of root exudates was efficient for promoting bacterial growth, ii) but a selective enrichment of PAH-degraders compared to aliphatic ones could be clearly demonstrated, thereby conducing to an enhanced PAH catabolism. The identification of plant secondary metabolites showed the presence of a broad range of flavonoid-derived compounds that could play a role in cometabolic processes. Microplate assays with the two major molecules, quercetin and rutin, suggested a partial involvement of these compounds in biostimulation processes. Further investigations with the other identified secondary metabolites (apigenin, isovitexin, catechin, gallic and caffeic acid) should provide more information on the exudate-PAH cometabolic degradation phenomenon.
植物修复被认为是一种有前途且具有成本效益的方法，可增强受污染土壤的生物修复。植物根系次生代谢物的分泌类似于有机污染物，可能诱导微生物降解酶的表达，并有利于外来化合物的共代谢。我们研究了芒草根系分泌物对多环芳烃（PAH）降解的生物刺激作用。选择这种多年生草是因为它能够在污染土壤上生长，并且能够用于非食品目的生产大量生物量。首先，评估了共代谢现象对菲降解细菌群落选择性富集的影响。在仅用菲、“菲+菲”、“菲+水杨酸”或“菲+柴油”孵育后，对每种分离菌株进行鉴定，结果表明，根据共底物的使用，细菌多样性和菲降解能力存在差异。然后，设计了一种微板测定法，该方法基于 PAH 和总根系分泌物存在时细菌群落生长和降解活性的同时测量。结果表明：i）添加根系分泌物可有效促进细菌生长；ii）但可以清楚地证明，与脂肪族化合物相比，对 PAH 降解物的选择性富集更为明显，从而增强了 PAH 分解代谢。植物次生代谢物的鉴定表明存在广泛的类黄酮衍生化合物，这些化合物可能在共代谢过程中发挥作用。使用两种主要分子槲皮素和芦丁进行微板测定表明，这些化合物部分参与了生物刺激过程。对其他鉴定出的次生代谢物（芹菜素、异荭草苷、儿茶素、没食子酸和咖啡酸）进行进一步研究，应能提供更多有关分泌物-PAH 共代谢降解现象的信息。
