夏季长江口海水中自由生活和颗粒附着古菌群落的组装过程研究

THE ASSEMBLING OF FREE-LIVING AND PARTICLE-ATTACHED ARCHAEA COMMUNITIES IN THE CHANGJIANG RIVER ESTUARY IN SUMMER

长江口位于长江和东海的重要交互区域,是研究海洋微生物生态作用的典型环境,但当前对海水中不同生活方式的海洋古菌在长江口的分布和组装过程尚未见系统的研究。采集夏季长江口海水中不同生活方式的古菌样品,基于宏基因组技术分析其多样性、分布特征和环境驱动因素,利用中性模型和零模型方法对其群落组装机制进行评估。研究结果显示泉古菌门(Crenarchaeota)是长江口古菌群落中的优势菌群。在科分类水平上,不同生活方式古菌群落组成存在差异,Marine Group II在自由生活状态(FL)中更加丰富,而Bathyarchaeia在颗粒附着状态(PA)中拥有更高的相对丰度。自由生活和颗粒附着古菌之间的相似性很高,说明多数古菌具有自由生活和颗粒附着的双重生活方式。对两种生活方式下古菌群落都有显著影响的重要环境因子是温度、盐度和硅酸盐含量;亚硝酸盐显著影响自由生活的古菌群落,叶绿素a显著影响颗粒附着的古菌群落(P<0.05)。结合中性模型和零模型,发现长江口海水中古菌群落的组装由随机性过程主导,生态漂变(76%贡献度)是颗粒附着古菌群落的主要组装方式,而对自由生活的古菌群落,其组装受到扩散限制、均质扩散和生态漂变的影响。

The Changjiang(Yangtze)River estuary is a typical area for studying the ecological role of marine microorganisms.However,there is no systematic study on the distribution and assembling of marine archaea in different lifestyles in the estuary.In this study,samples of archaea with different lifestyles were collected from seawater of the estuary in summer.Metagenomic technology was used to sequence the archaea;and their diversity,distribution,and environmental drivers were analyzed.Neutral and null model methods were used to study the mechanism of community assembling.Results show that the Crenarchaeota was the dominant archaea in the estuary.At family level,compositions of archaeal communities varied with lifestyle state.For examples,Marine GroupⅡwas more abundant in free-living state,while Bathyarchaeia was richer in particle-attached state.Similarity between free-living and particle-attached archaea was high,indicating that most archaea could live in a dual life styles of free-living and particle-attachment.Temperature,salinity,and silicate content were key factors affecting remarkably the archaeal communities of both lifestyles.Nitrite affected significantly the free-living archaea community,and chlorophyll-a significantly affected the particle-attached archaea community.As revealed in the neutral model and zero model,assembling of the archaea community in the estuary was controlled by stochastic processes,and ecological drift(76%in contribution)was the main assembling way of particles adhesion.For the free-living life of archaea community,the assembling relied on the diffusion limit,homogeneous diffusion,and ecological drift.