Aquatic Ecology and Water Quality Management Group, Wageningen University, P.O. Box 47, 6700 AA, Wageningen, the Netherlands; State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China.
State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China; SCNU Environmental Research Institute, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Environmental Theoretical Chemistry, South China Normal University, Guangzhou, 510006, China.
Aquat Toxicol. 2019 Jul;212:11-19. doi: 10.1016/j.aquatox.2019.04.015. Epub 2019 Apr 18.
Triclosan (TCS, 5-chloro-2-(2,4-dichlorophenoxy) phenol) is a broad-spectrum antimicrobial compound. Owing to its wide use, TCS has been frequently detected in river systems, especially in the (sub-)tropics. However, little information on its interaction with river biofilm in the (sub)tropics is currently available. In the present study, subtropical river biofilms were chronically exposed to TCS for 14 d at concentrations of 0.1-100 μg/L in artificial river water, which was followed by a 7 d recovery period. The results show that 100 μg/L TCS inhibited the growth of river biofilms and the no-observed-effect concentration (NOEC) of TCS on river biofilms was 10 μg/L. The affected biofilms did not completely recover within the 7 d of recovery period due to the adsorbed TCS which was not removed together with dissolved TCS. Exposure to TCS caused significant changes in prokaryotic species composition of river biofilms but no significant effects on eukaryotic species composition. In particular, the relative abundance of several TCS-tolerant bacterial species (e.g., Pseudoxanthomonas mexicana, Sphingopyxis alaskensis and Sphingomonas wittichii) in river biofilms increased following exposure to 10 and 100 μg/L TCS. River biofilm efficiently removed TCS from the liquid phase and the pH values of the aquatic system significantly affected the removal efficiency of TCS (from 36% at pH 6.5 to 60% at pH 8.5). No degradation products were detected in the liquid phase after 5 days of exposure, possibly due to strong adsorption of the hydrophobic degradation products to river biofilms and through biodegradation by bacteria utilizing TCS and its degradation products as source of carbon and energy for growth, such as Methyloversalitis universalis and Methylobacterium aquaticum.
三氯生（TCS，5-氯-2-（2,4-二氯苯氧基）苯酚）是一种广谱抗菌化合物。由于其广泛的用途，TCS 经常在河流系统中被检测到，特别是在（亚热带）热带地区。然而，目前关于其与（亚热带）热带河流生物膜相互作用的信息很少。在本研究中，采用人工河水，将亚热带河流生物膜在 0.1-100μg/L 的 TCS 浓度下慢性暴露 14 天，随后进行 7 天的恢复期。结果表明，100μg/L 的 TCS 抑制了河流生物膜的生长，TCS 对河流生物膜的无观察效应浓度（NOEC）为 10μg/L。由于与溶解的 TCS 一起未去除被吸附的 TCS，受影响的生物膜在 7 天的恢复期内并未完全恢复。TCS 的暴露导致河流生物膜中原核物种组成发生显著变化，但对真核物种组成没有显著影响。特别是，在暴露于 10 和 100μg/L TCS 后，几种 TCS 耐受细菌物种（如 Pseudoxanthomonas mexicana、Sphingopyxis alaskensis 和 Sphingomonas wittichii）在河流生物膜中的相对丰度增加。河流生物膜从液相中有效地去除了 TCS，并且水系统的 pH 值显著影响了 TCS 的去除效率（从 pH 6.5 时的 36%到 pH 8.5 时的 60%）。在暴露 5 天后，液相中未检测到降解产物，这可能是由于疏水性降解产物强烈吸附在河流生物膜上，以及通过细菌利用 TCS 及其降解产物作为生长的碳源和能源进行生物降解所致，如 Methyloversalitis universalis 和 Methylobacterium aquaticum。
