夏季珠江口冲淡水对氨氧化古菌的空间演替及分布规律的影响

Community structures and activities of ammonia oxidizing archaea influenced by runoff input of Pearl River Estuary during summer

氮在海洋生物地球化学循环中起着重要的作用,通常能限制海洋生物的生产力.硝化反应是氮循环的核心环节,且氨氧化反应是硝化作用的限速步骤,再加上氨氧化古菌(Ammonia Oxidizing Archaea,AOA)是氨氧化反应的主力军,因此海洋氨氧化古菌成了研究热点.通过对夏季珠江口的不同深度水体进行研究,以氨氧化古菌的功能基因氨单加氧酶(amoA)作为分子标记,运用454高通量测序技术和定量PCR在DNA和cDNA水平上来分析氨氧化古菌的群落结构组成、多样性和基因丰度分布特征.结果表明,夏季珠江口的淡水来源站位(A2B)有着最高的氨氧化古菌群落多样性,但丰度最低;自由生活型的氨氧化古菌丰度是附着生活型的10~1000倍,这可能是氨氧化古菌的主要生存策略;盐度是影响夏季珠江口氨氧化古菌群落结构组成的主要环境因子,而其amoA基因丰度与环境因子之间没有显著性差异;表层和底层AOA群落之间的差异较自由生活的与附着的群落之间更为明显.研究表明在cDNA水平上对功能微生物类群进行探究的必要性,有助于增进水体氨氧化古菌群落响应环境变迁的认识.

Nitrification is the core part of the nitrogen cycle and ammonia oxidation is the rate-limiting step of nitrification,therefore,ammonia oxidizing archaea(AOA)as the main force of ammonia oxidation reaction has become a research hotspot.With AOA amoA gene as the molecular marker,this study uses 454 pyrosequencing and quantitative PCR with seawater collected from the Pearl River Estuary during summer with runoff input to investigate the community structures and activities of free-living and attached AOA communities at both DNA and cDNA levels.In summer,the station of mainly freshwater source(A2B)in the Pearl River Estuary had the highest AOA community diversity but the lowest amoA gene abundances.The abundance of free-living AOA was 10-1000 times higher than those attached ones.Salinity was the main environmental factor affecting the community structures of AOA,however,there was no significant relationship between the environmental factors and the AOA amoA gene abundance.Distinct AOA community structures existed between the surface and bottom,and was more obvious than the difference between free-living and attached fractions.This study highlighted the necessity of studying functional groups at the cDNA levels,and provided insight into the influence of environmental variation on the population shifts of AOA in the aquatic ecosystems.