Methane production pathways and methanogenic archaeal community structures in sediment of Wuxijiang River.

内容摘要

Rivers are hotspots of global methane (CH4) emissions. We collected sediments from the upstream, midstream, and downstream reaches of the Wuxijiang River. Combined with anaerobic slurry incubation experiments and molecular biological techniques, we examined the spatial distribution of methanogenic pathways, as well as the abundance and community composition of methanogenic archaea. Results showed that hydrogenotrophic pathway (with H2 and CO2 as substrates) predominated across all reaches. The potential of this pathway reached its maximum in the middle reach. Quantitative PCR showed that mcrA gene abundance in the middle reach (1.44×108 copies·g-1) was significantly higher than that in the upper (9.18×107 copies·g-1) and lower reaches (1.01×108 copies·g-1). High-throughput sequencing indicated that the diversity of methanogenic archaea was significantly higher in the upper reach than in the middle and lower reaches, with community structure varying significantly among reaches. The methanogenic community in the upper and middle reaches was dominated by Methanoregula, Methanobacterium and Methanosarcina, whereas that in the lower reach was dominated by Methanoregula and Methanolinea. The relative abundance of Methanoregula showed an increasing trend from upstream (36.2%) to midstream (54.9%) and downstream (61.0%). Correlation analyses indicated that sediment organic carbon contents, NH4+-N contents, and pH were significantly associated with the spatial heterogeneity of methanogenic pathways and methanogenic archaeal community composition. Collectively, the midstream reach represented a potential hotspot of CH4 production in the Wuxijiang River, and these findings would provide new insights into the spatial heterogeneity of methane emissions in mountainous river system. 河流是全球甲烷(CH4)排放的热点区域之一。本研究以乌溪江上、中、下游河段沉积物为研究对象,通过室内厌氧泥浆培养试验及分子生物学技术,分析其产甲烷途径、产甲烷古菌丰度和群落组成的空间分布特征。结果表明:氢营养型(以H2和CO2为底物)是不同河段的优势产甲烷途径,且该途径的潜势在中游河段达到峰值,显著高于其他河段。定量PCR结果发现,中游河段的产甲烷古菌mcrA基因丰度(1.44×108 copies·g-1)显著高于上游(9.18×107 copies·g-1)和下游(1.01×108 copies·g-1)。高通量测序结果显示,上游河段产甲烷古菌多样性显著高于中游和下游,且不同河段产甲烷古菌的群落结构存在显著差异,上、中游河段群落组成以甲烷规则菌属、甲烷杆菌属和甲烷八叠球菌属为主,下游河段以甲烷规则菌属和甲烷绳菌属为主。其中,甲烷规则菌属的相对丰度由上游(36.2%)、中游(54.9%)至下游(61.0%)逐渐增加。相关性分析表明,沉积物有机碳、NH4+-N含量及pH是与产甲烷途径和产甲烷古菌群落组成空间异质性显著相关的关键环境因子。综上,中游河段是乌溪江CH4产生的潜在热点区域,研究结果有助于深入理解高山河流CH4排放的空间异质性特征。.