城市河流沉积物中氮素与好氧甲烷氧化菌群落特征响应关系

由于人类活动的影响大量未经处理的废污水汇入城市河流,高浓度的污染物影响了河流中微生物对生物地球化学物质迁移和转化的介导作用.本文选取典型的城市河流——北运河作为研究区域,分析了北运河沉积物中氮素形态以及含量的空间和季节差异性,并结合克隆文库分子生物学的方法,探讨了氮素形态和含量的差异对好氧甲烷氧化菌(aerobic methane-oxidizing microorganisms,MOB)群落特征的影响.结果表明:北运河沉积物中铵态氮(NH_4~+-N)为氮素的主要存在形态,存在显著的空间差异,其含量在下游显著高于上游,但季节差异不显著.NH_4~+-N含量的空间差异对MOB的群落结构和群落分布有显著影响,对群落多样性影响不显著.NH_4~+-N含量的空间分布特征与MOB的群落聚类特征一致,NH_4~+-N对MOB群落分布的影响显著高于其他形态的氮素,其含量越高,则与MOB群落分布的响应关系越紧密.北运河中NH_4~+-N的来源影响了沉积物中MOB的主要来源,MOB高同源性菌群的来源与NH_4~+-N等主要污染物的来源一致.沉积物中MOB物种之间联系的紧密程度依赖于氮素的主要存在形态及其含量水平.NH_4~+-N含量较高的下游沉积物中微生物彼此之间关系及集聚程度更强,受外界环境变化的干扰程度更强,受人类活动引起环境变化的敏感程度更高.城市河流中氮素的形态和含量差异对甲烷的氧化过程有显著影响.探究城市河流沉积物中高含量的NH_4~+-N对甲烷产生及消耗的影响过程是控制河流温室气体排放的关键.

The response relationship between nitrogen and aerobic methanotrophs in sediment of urban river, Beijing, China

Stream ecosystems are the main receivers of nutrient and organic carbon exported from terrestrial ecosystems. Stream ecosystems are profoundly influenced by the land used in the surrounding area. Anthropogenic activities increase the amount of nutrient and organic carbon in both stream and benthic biofilms, which are closely related to differences in the aerobic methane-oxidizing microorganisms (MOB) bacteria microbial communities. We studied MOB bacteria microbial communities in the North Canal, Beijing, China. The results showed that the main form of nitrogen was ammonium nitrogen (NH₄⁺-N) in the North Canal. There are not any significant differences of the NH₄⁺-N between summer and winter, whereas there are significant differences between midstream and downstream. Results of heatmap analysis were closely related to the difference of the NH₄⁺-N in spatial. Phylogenetic analysis indicated that most of the cloned pmoA sequences in the North Canal were similar to those sequences from activated sludge and wastewater. The effect of nitrogen on MOB bacteria in the North Canal mainly depends on the main form of nitrogen and the source of pollutants. Moreover, MOB bacteria in downstream of the North Canal, had a more closer and modular microbial network than midstream, where bacteria communities with tightly connected species had proven to be more vulnerable and sensitive to various disturbances.