School of Environment, Beijing Normal University, State Key Laboratory of Water Environment Simulation, Beijing 100875, China.
School of Environment, Beijing Normal University, State Key Laboratory of Water Environment Simulation, Beijing 100875, China.
Chemosphere. 2015 Jun;128:236-44. doi: 10.1016/j.chemosphere.2015.02.011. Epub 2015 Feb 25.
The degrading genes of hydrophobic organic compounds (HOCs) serve as indicators of in situ HOC degradation potential, and the existing forms and bioavailability of HOCs might influence the distribution of HOC-degrading genes in natural waters. However, little research has been conducted to study the relationship between them. In the present study, nahAc and nidA genes, which act as biomarkers for naphthalene- and pyrene-degrading bacteria, were selected as model genotypes to investigate the response of polycyclic aromatic hydrocarbon (PAH)-degrading genes to PAH bioavailability in the overlying water, suspended sediment (SPS), and deposited sediment of the Yangtze River. The freely dissolved concentration, typically used to reflect HOC bioavailability, and total dissolved, as well as sorbed concentrations of PAHs were determined. Phylogenetic analysis showed that all the PAH-ring hydroxylating dioxygenase gene sequences of Gram-negative bacteria (PAH-RHD[GN]) were closely related to nahAc, nagAc, nidA, and uncultured PAH-RHD genes. The PAH-RHD[GN] gene diversity as well as nahAc and nidA gene copy numbers decreased in the following order: deposited sediment>SPS>overlying water. The nahAc and nidA gene abundance was not significantly correlated with environmental parameters but was significantly correlated with the bioavailable existing forms of naphthalene and pyrene in the three phases. The nahAc gene copy numbers in the overlying water and deposited sediment were positively correlated with freely dissolved naphthalene concentrations in the overlying and pore water phases, respectively, and so were nidA gene copy numbers. This study suggests that the distribution and abundance of HOC-degrading bacterial population depend on the HOC bioavailability in aquatic environments.
疏水性有机化合物（HOCs）的降解基因可作为原位 HOC 降解潜力的指示物，而 HOCs 的现有形态和生物可利用性可能影响天然水中 HOC 降解基因的分布。然而，目前关于它们之间的关系研究甚少。本研究选择萘和芘降解菌的 nahAc 和 nidA 基因作为模式基因型，以研究多环芳烃（PAH）降解基因对长江水体、悬浮颗粒物（SPS）和底泥中 PAH 生物可利用性的响应。测定了自由溶解浓度（通常用于反映 HOC 生物可利用性）以及总溶解浓度和 PAHs 的吸附浓度。系统发育分析表明，所有革兰氏阴性菌的多环芳烃环羟化双加氧酶基因序列（PAH-RHD[GN]）均与 nahAc、nagAc、nidA 和未培养的 PAH-RHD 基因密切相关。PAH-RHD[GN]基因多样性以及 nahAc 和 nidA 基因拷贝数按以下顺序降低：底泥>SPS>水体。 nahAc 和 nidA 基因丰度与环境参数无显著相关性，但与三种相中萘和芘的生物可利用现有形态显著相关。水体和底泥中 nahAc 基因拷贝数与上覆水和孔隙水中自由溶解萘浓度呈正相关，nidA 基因拷贝数也是如此。本研究表明，HOC 降解菌种群的分布和丰度取决于水生态环境中 HOC 的生物可利用性。
