九龙江河口区微生物多样性及群落结构的时空分布

Phylogenetic diversity and spatiotemporal patterns of the bacterial community in Jiulong River estuary

河口区由于其独特的地理环境和理化条件,拥有丰富的微生物资源,在生物地球化学循环中起着重要作用.然而,由于人类活动带来的河口区环境因素改变,引起的微生物群落结构的时空变化目前还知之甚少.本研究选取九龙江河口区7个近年来遭受较为严重人类活动干扰的采样点,分别在丰水期和枯水期采集表层水体,采用流动注射法测定了水体的三氮、电导率、pH值和溶解性磷酸盐等环境参数,采用海水和淡水培养基,基于纯培养技术分析了可培养细菌的总数和分布特征,并通过构建16S rRNA基因克隆文库的方法研究细菌的多样性和群落结构变化.研究表明,变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes)是各克隆文库中最优势的类群.在河口下游海水区,变形菌门微生物与放线菌门微生物的比例约为2∶1~3∶1,而在河口上游淡水区,变形菌门和放线菌门的比例约为1∶1.在河口下游海水区,α变形菌纲(Alphaproteobacteria)为变形菌门中的优势类群,而在河口上游淡水区,β变形菌纲(Betaproteobacteria)为优势类群.厚壁菌门(Firmicutes)是克隆文库中丰度占第四的类群,说明水体可能遭受畜牧养殖粪便污染.本研究表明,九龙江河口区微生物群落结构受水体盐度、温度、水文情况等时空因子及人类活动造成的营养物浓度上升、动物粪便污染等共同影响,呈现出独特的时空分布特点.

Estuary ecosystems are important water sources with microorganisms as key components playing crucial roles in global biogeochemical cycles. However, the spatiotemporal variation in the distribution and abundance of microbes as well as the response to anthropogenic environmental changes are still poorly understood. In this study, seven sampling sites were selected in Jiulong River estuary, which has experienced intensive human perturbation in recent years. The changes in the diversity and structure of microbial community were analyzed while the environ-mental factors were determined both in rainy and dry seasons. The results of 16S rRNA gene clone libraries indica-ted that Proteobacteria, Actinobacteria and Bacteroidetes were the most predominant groups. Both in rainy and dry seasons, the ratio of Proteobacteria to Actinobacteria was about 2： 1 ？3： 1 in the upper reaches while about 1： 1 in the lower reaches. At the level of class, Betaproteobacteria dominated the phylum of Proteobacteriain in the upper reaches but Alphaproteobacteria were the majority in the lower reaches. Firmicutes were the fourth abundant group in dry season, implying the contaminated water bodies by fecal pollution. Our study demonstrated that the microbial community in Jiulong River estuary was sensitive to human-caused environmental changes and displayed a distinct spatiotemporal pattern driven by salinity, nutrients, temperature, river flow and contamination such as animal feces.