渤海沉积环境中细菌汞还原酶基因merA 的多样性分析

摘要

细菌汞还原酶 MerA 对环境中的汞具有潜在的还原和解毒作用。本研究对2011－2012年采自渤海湾天津滨海新区大沽河排污河口、渤海湾近岸及莱州湾垦利养殖区的表层沉积物，进行了放线菌门、厚壁菌门、α－变形菌纲和β／γ－变形菌纲汞还原酶基因 merA 克隆文库的构建和序列测定，并对merA 基因序列编码的 MerA 蛋白序列进行分析。结果表明：渤海沉积环境中发育多样性丰富的MerA，排污河口和养殖区中厚壁菌门、α－变形菌纲和α／β／γ－变形菌纲的 MerA 多样性均高于渤海湾近岸的。3个区域具有不同的 MerA 组成特征，厚壁菌门中与 Bacillus sp．MB2021亲缘关系最近的 MerA 的总丰度在养殖区最高（24．3％），与 Paenisporosarcina sp．TG20亲缘关系最近的 MerA 的总丰度在排污河口最高（46．3％）。不同环境背景、外源 merA 基因输入、汞等重金属污染物的联合选择可能导致了渤海沉积环境中 MerA 多样性和组成的变化。%Mercuric reductase gene merA had a potential role in mercuric reduction and detoxification in environ-ment.During 2011-2012,surface sediments were collected from wastewater discharge of Dagu River in Tianjin Binhai New Area from Bohai Bay,near shore of Bohai Bay and Kenli aquaculture facility from Laizhou Bay.Clone libraries of merA from Actinomycete,Firmicutes,α-Proteobacteria andβ/γ-Proteobacteria were constructed and the sequences were determined.Deduced MerA protein sequences of merA gene were then analyzed.The results showed that Bohai Sea sedimentary environment contained high diversity of MerA,and MerA diversity within Fir-micutes,α-Proteobacteria andα/β/γ-Proteobacteria from wastewater discharge and aquaculture facility were higher than that in near shore of Bohai Bay.The MerA composition in different locations also differed,and within Firmi-cutes,the highest total abundance of MerAs that had the highest similarity with Bacillus sp.MB2021 was found in aquaculture facility(24.3%),while,the highest total abundance of MerAs that had the highest similarity with Paenisporosarcina sp.TG20 was found in wastewater discharge(46.3%).Different environment context,exoge-nous merA gene input,and co-selection caused by mercury and other heavy metal pollutants might together lead to the change of merA diversity,community composition in Bohai Sea sedimentary environment.