三沙永乐龙洞内沉积物细菌种群特征

三沙永乐龙洞是世界已知最深的海洋蓝洞，洞内存在有别于一般海洋环境的生物群落和物质循环。本文采用高通量测序技术获得三沙永乐龙洞内沉积物中的细菌种群组成特征，以期为揭示细菌在蓝洞内物质循环中的作用提供基础数据。2017年3月在三沙永乐龙洞内约150 m深处斜坡相距10 m（152 m和162 m深处）和洞底300 m三个深度收集沉积物样品，采用Illumina MiSeq测序技术，比较研究三个不同深度沉积物中的细菌种群特征。测序共获得121690条优质序列，分类分析共检测出53个门、301个属和546种细菌。152 m、162 m和300 m深度沉积物中的细菌种群Shannon多样性指数分别为5.66、5.72和5.55。三个深度沉积物细菌种群在组成及其相对丰度上都存在明显差异，同时物种组成上又存在一定相似性和重叠情况，如Chloroflexi（绿弯菌门）和Proteobacteria（变形菌门）在三个深度沉积物中都为优势门，但其相对丰度不同，Chloroflexi的相对丰度分别为44.73%（152 m）、18.42%（162 m）和4.98%（300 m），Proteobacteria的相对丰度分别为13.29%（152 m）、23.00%（162 m）和44.88%（300 m）。分类分析还发现了很多参与硫素循环的菌类，如绿硫细菌、脱硫酸盐还原菌、脱硫酸盐菌、脱硫球菌、硫微螺菌等，它们在不同深度沉积物中的相对丰度存在明显差异，表明在龙洞沉积物中硫素循环非常活跃，同时在不同深度沉积物中细菌参与的硫素循环步骤明显不同。

Bacterial population characteristics of sediment from Sansha Yongle Blue Hole,China

Sansha Yongle Blue Hole is the deepest marine blue hole for the known ones in the world.Microorganisms play critical roles in this special ecosystem of the marine blue hole.In order to reveal the bacterial role in material cycle of the blue hole, the bacterial community characteristics in sediment from Sansha Yongle Blue Hole was detected using high-throughput barcoded pyrosequencing of 16S rRNA gene.There was a ledge with sediment in about 150 m depth, so the sediment samples were collected from the ledge (152 m and 162 m depth with 10 m distance) and the bottom of the blue hole (about 300 m depth).The bacterial population at three different depth was compared by analyzing sequencing data from Illumina Miseq.A total of 121 690 high-quality partial 16S rDNA sequences were obtained by Miseq sequencing analysis.Those sequences were assigned to 53 phyla, 301 genera and 546 species.The Shannon index at 152 m, 162 m and 300 m were 5.66, 5.72 and 5.55, respectively.Both the dominants and their relative abundance varied significantly at different depth, while some dominants were resemble and overlap.For example, both Chloroflexi and Proteobacteria were dominant phyla among the three samples, but their relative abundance varied significantly:the relative abundance of Chloroflexi was 44.73% at 152 m, 18.42% at 162 m and 4.98% at 300 m, while Proteobacteria was 13.29% at 152 m, 23.00% at 162 m and 44.88% at 300 m.Some bacteria participating in the sulfur cycle were found, such as Chlorobi, Desulfobacteraceae, Desulfatiglans, Desulfococcus, Thiomicrospira and so on, indicating that the sulfur cycle was very active in this marine blue hole.Otherwise the relative abundance of those bacteria was different clearly at the different depth, suggesting the step participating in sulfur cycle varied obviously.