Istituto di Ricerca Sulle Acque (IRSA), CNR, Via Salaria km 29.300, 00015 Monterotondo Scalo, RM, Italy; Dipartimento di Science Ecologiche e Biologiche (DEB), Universita degli studi della Tuscia, Via San Camillo de Lellis, 01100 Viterbo, Italy; Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), CSIC, Avenida Reina Mercedes, 10, E-41012 Seville, Spain.
Departament de Microbiologia, Universitat de Barcelona, Avenida Diagonal 643, 08028 Barcelona, Spain; Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), CSIC, Avenida Reina Mercedes, 10, E-41012 Seville, Spain.
Sci Total Environ. 2020 May 15;717:137210. doi: 10.1016/j.scitotenv.2020.137210. Epub 2020 Feb 8.
The risks of pollution by polycyclic aromatic hydrocarbons (PAHs) may increase in bioremediated soils as a result of the formation of toxic byproducts and the mobilization of pollutants associated to suspended colloids. In this study, we used the motile and chemotactic bacterium Pseudomonas putida G7 as an experimental model for examining the potential role of bacterial motility in the cometabolism and biosorption of pyrene in a porous medium. For this purpose, we conducted batch and column transport experiments with C-labelled pyrene loaded on silicone O-rings, which acted as a passive dosing system. In the batch experiments, we observed concentrations of the C-pyrene equivalents well above the equilibrium concentration observed in abiotic controls. This mobilization was attributed to biosorption and cometabolism processes occurring in parallel. HPLC quantification revealed pyrene concentrations well below the C-based quantifications by liquid scintillation, indicating pyrene transformation into water-soluble polar metabolites. The results from transport experiments in sand columns revealed that cometabolic-active, motile cells were capable of accessing a distant source of sorbed pyrene. Using the same experimental system, we also determined that salicylate-mobilized cells, inhibited for pyrene cometabolism, but mobilized due to their tactic behavior, were able to sorb the compound and mobilize it by biosorption. Our results indicate that motile bacteria active in bioremediation may contribute, through cometabolism and biosorption, to the risk associated to pollutant mobilization in soils. This research could be the starting point for the development of more efficient, low-risk bioremediation strategies of poorly bioavailable contaminants in soils.
多环芳烃 (PAHs) 的污染风险可能会由于有毒副产物的形成和与悬浮胶体相关的污染物的迁移而在生物修复土壤中增加。在这项研究中，我们使用游动和趋化细菌假单胞菌 G7 作为实验模型，研究细菌运动性在多孔介质中芘的共代谢和生物吸附中的潜在作用。为此，我们进行了批次和柱传输实验，使用 C 标记的芘加载在硅橡胶 O 型圈上，作为被动给药系统。在批处理实验中，我们观察到 C-芘当量的浓度远高于在非生物对照中观察到的平衡浓度。这种迁移归因于同时发生的生物吸附和共代谢过程。HPLC 定量显示芘浓度远低于液体闪烁法的 C 基定量，表明芘转化为水溶性极性代谢物。砂柱传输实验的结果表明，共代谢活性的游动细胞能够进入吸附芘的遥远来源。使用相同的实验系统，我们还确定了被水杨酸动员但因趋化行为而被抑制共代谢的细胞能够吸附该化合物并通过生物吸附将其动员。我们的结果表明，在生物修复中活跃的游动细菌可能通过共代谢和生物吸附，对土壤中污染物迁移带来的风险做出贡献。这项研究可能为开发更有效、低风险的土壤中生物利用度差的污染物的生物修复策略提供起点。
