青藏高原北部湖泊表层沉积物参与卡尔文循环的固碳基因多样性及其影响因素

Gene Diversity Involved in Kalvin Pathway of Carbon Fixation and Its Response to Environmental Variables in Surface Sediments of the Northern Qinghai-Tibetan Plateau Lakes

研究青藏高原北部湖泊表层沉积物参与卡尔文循环固碳基因多样性及其对盐度的响应.采用构建克隆文库、聚合酶链式反应、rbcL基因系统发育分析等方法,研究青藏高原6个典型湖泊(洱海、青海湖、托素湖、尕海、小柴旦湖、茶卡盐湖)表层沉积物微生物rbcL基因多样性,揭示不同湖泊中固碳微生物种群构成,同时初步分析各个湖泊中固碳微生物种群组成与环境参数的关系.结果显示:所有表层沉积物样品中固碳微生物共分3个门,即:变形菌门(Proteobacteria)、蓝藻门(Cyanobacteria)和绿藻门(Chlorophyta),分属于以下8个纲:Acidithiobacillia、α-Proteobacteria、β-Proteobacteria、γ-Proteobacteria、Chroococcidiopsidales、Oscillatoriophycideae、Synechococcales和Chlorophyceae.其具体分布情况有较大差异,从整体上分为3大类:在淡水湖泊(洱海)中,Synechococcales纲是主要固碳菌群,相对丰度为71.32%;在咸水湖泊(青海湖、托素湖)中,β-Proteobacteria纲、Synechococcale纲和Oscillatoriophycideae纲是主要固碳菌群,相对丰度分别是36.20%、23.47%和22.02%;在超盐湖泊(尕海、小柴旦湖、茶卡盐湖)中,Acidithiobacillia纲和Chlorophyceae纲是主要固碳菌群,相对丰度分别是53.33%和30.40%. Mantel检验结果显示,固碳微生物群落分布与盐度、溶解有机碳(DOC)、总磷、总氮、溶解无机碳(DIC)、pH及叶绿素a浓度存在显著的相关关系(P <0.05).ABT进一步分析显示,总磷对微生物群落的影响强度最大,相对影响强度百分比是20.04%.其次是盐度,相对影响强度百分比是16.81%.变形菌门(主要为Acidithiobacillia)和Synechococcale纲是青藏高原北部表层沉积物主要固碳微生物.不同盐度环境中的固碳微生物群落组成差异较大,盐度相似的环境中固碳微生物群落组成相似.因此,盐度和总磷是影响湖泊固碳微生物群落分布的主要因素.

To study the gene diversity involved in the Kalvin pathway of carbon fixation and its response to environmental variables in the lake surface sediments on the northern Qinghai-Tibetan plateau. In this study, we collected surface sediments from six typical lakes（Erhai Lake, Qinghai Lake, Tuosu Lake, Gahai Lake, Xiaochaidan Lake, Chaka Lake） on the Qinghai-Tibetan plateau. The carbon-fixing bacteria diversity in the collected samples was investigated by using the rbcL gene-based phylogenetic analysis. Correlation analysis was performed between the rbcL gene diversity and environmental parameters of the studied lakes. The phylogenetic analyses show that the rbcL gene population in the studied samples are classified into three phyla, i.e. Proteobacteria, Cyanobacteria, and Chlorophyta, and into eight classes, i.e. Acidithiobacillia, α-Proteobacteria,β-Proteobacteria, γ-Proteobacteria, Chroococcidiopsidales, Oscillatoriophycideae, Synechococcales, and Chlorophyceae. In the freshwater lakes（Erhai Lake）, the Synechococcales-related clones are dominant（the relative abundance is 71.32%）; In the saline lakes（Qinghai Lake, Tuosu Lake）,β-Proteobacteria, Synechococcale, and Oscillatoriophycideae are dominant classes（the relative abundances are 36.20%, 23.47%, and 22.02%,respectively）; In the hypersaline lakes（Gahai Lake, Xiaochaidan Lake, Chaka Lake）, Acidithiobacillia and Chlorophyceae are dominant classes（the relative abundances are 53.33% and 30.40%, respectively）. The rbcL gene population composition show significant（p 0.05） correlations with salinity, dissolved organic carbon（DOC）, TP, TN, dissolved inorganic carbon（DIC）, pH and chlorophyll-a. Aggregated boosted tree（ABT）analyses show that TP and salinity are the two factors contributing the most（accounting for 20.04% and 16.81% of the microbial variation） to shaping carbon fixing microbial communities in the studied lakes. The majority of the rbcL gene population is affiliated with the Proteobacteria（mainly Acidithiobacillia） and Synechococcale in the studied lake surface sediments. The rbcL gene population composition varies significantly among the studied lakes of different salinities, and the lacustrine habitats with similar salinities possess similar rbcL gene population. In summary,TP and salinity is an important factor affecting the distribution of carbon-fixing bacterial population.