闽江河口区淡水和半咸水潮汐沼泽湿地土壤产甲烷菌多样性

为认识盐度对河口潮汐沼泽湿地土壤产甲烷菌的影响,应用PCR-RFLP技术及测序分析对闽江河口区淡水-半咸水盐度梯度上分布的4个短叶茳芏潮汐沼泽湿地土壤产甲烷菌群落结构进行研究。闽江河口区短叶茳芏潮汐沼泽湿地土壤产甲烷菌群落结构受盐度影响明显,位于下洋洲和塔礁洲的短叶茳芏潮汐淡水沼泽湿地土壤产甲烷菌的香农-威纳多样性指数值分别为2.81和2.65,位于蝙蝠洲和鳝鱼滩的短叶茳芏潮汐半咸水沼泽湿地土壤产甲烷菌香农-威纳多样性指数值分别仅为2.33和2.27。系统发育分析表明:短叶茳芏沼泽湿地土壤产甲烷菌类群主要有甲烷杆菌目(Methanobacteriales),包括Methanobacterium、Methanobrevibacter和Methanobacteriaceae;甲烷微菌目(Methanomicrobiales),主要有Methanoregula,以及甲烷八叠球菌目(Methanosarcinales),主要有Methanosarcina和Methanococcoides。闽江河口区短叶茳芏潮汐淡水沼泽湿地土壤主要的优势产甲烷菌有Methanoregula、Methanosarcina和Methanobacterium,而短叶茳芏潮汐半咸水沼泽湿地土壤主要的优势产甲烷菌则转化为仅以Methanoregula为主。

Diversity of methanogen communities in tidal freshwater and brackish marsh soil in the Min River estuary

Methane is one of the main greenhouse gases and plays an important role in global climate change. Wetlands are the main source of global methane emission. Microbial communities inhabiting anoxic habitats such as freshwater wetlands and marine sediment are important for biological carbon cycling. Methanogenesis is the final step of degradation of organic substrates and mediated by methanogenic archaea. Rising sea levels and excessive water withdrawals upstream are making previously freshwater wetlands saline. Plant community responses to change in the freshwater-saline gradient have been well studied in the estuarine wetlands; however, microbial community structure response to salinity gradient remains relatively unexplored, including the methanogens in tidal marsh soil along salinity gradient in subtropical estuary are poorly characterized.It is essential to investigate the influence of salinity on the community structure of methanogen in tidal marshes. With the development of molecular biological techniques, molecular methods independent of culture techniques has vastly improved the potential to describe microbial diversity.Methyl-coenzyme M reductase is a critical enzyme in methanogenesis and the mcrA gene is a favorable functional gene and widely used to detect methanogens in soils of wetlands.Here, we determined the diversity of methanogen communities using molecular technique targeting the mcrA gene and restriction fragment length polymorphism (RFLP) from the soil of the tidal freshwater and brackish Cyperus malaccensis marshes in the Min River estuary, southeast China. The community structure of methanogen in the tidal C. malaccensis marshes changed with salinity. Values of Shannon-Weiner index of methanogen from the soil of tidal freshwater C. malaccensis marshes are 2.81 and 2.65 in the Xiayangzhou and Tajiaozhou wetlands, and 2.33 and 2.27 in the soil of tidal brackish C. malaccensis marshes in the Bianfuzhou and Shanyutan wetlands. The diversity of methanogen communities from the tidal C. malaccensis marshes decreased with increasing salinity in the Min River estuary. Phylogenetic analysis revealed that the communities of methanogens in the C. malaccensis marshes were mainly divided into three groups which were Methanomicrobiales, Methanosarcinales and Methanobacteriales. The freshwater C. malaccensis marshes were mainly dominated by Methanoregula,Methanosarcina and Methanobacterium.However, the brackish C. malaccensis marshes only dominated by Methanoregula. We conclude that methanogen diversity in estuarine tidal marshes is shaped by salinity conditions, suggesting an influence of impending sea level rise.