南海北部陆坡神狐海域HS-PC500岩心微生物多样性

Microbial diversity in sediments of core HS-PC 500 from Shenhu Area,northern South China Sea

【目的】本文研究南海北部陆坡神狐HS-PC500重力活塞岩心沉积物中微生物多样性。【方法】使用吖啶橙染色法计数沉积物中微生物丰度;提取沉积物微生物总DNA,使用特异性引物扩增古菌及细菌16SrRNA基因序列;对克隆文库进行系统发育分析。【结果】系统发育分析显示表层PC500-1(0-5 cm belowsea floor,bsf)古菌以C3为主要类群,占该层总序列的25.6%;中层PC500-6(350-355 cm bsf)和底层PC500-11(790-795 cm bsf)古菌以Marine Benthic Group(MBG)-B为主要类群,分别占该层总序列的48.1%和38.9%。另有部分克隆序列属于MBG-A、Miscellaneous Crenarchaeotic Group(MCG)、Thermoprotei、NGC、Halobacteriales、MBG-E、South African Gold Mine Euryarchaeotic Group(SAGMEG)。表层细菌以变形菌(Proteobacteria)为主要类群,占该层文库的38.3%。中层和底层细菌以绿弯菌(Choloflexi)和JS1为主要类群,分别占该层文库的28.1%、29.2%和39%、24.7%。另有部分克隆序列属于硝化螺旋菌(Nitrospirae)、放线菌(Actinobacteria)、酸杆菌(Acidobacteria)、OP8、螺旋体菌(Spirochaetes)、TM6、脱铁杆菌(Deferribacteres)、浮霉菌(Plantomycete)。【结论】结果显示,HS-PC500岩心微生物丰度与甲烷浓度变化相吻合;微生物丰度较低可能与较低的总有机碳量有关;微生物多样性较高,并且随深度的增加群落结构变化明显;岩心中有关硫酸盐还原的微生物类群占优势,说明微生物的硫代谢在该海区沉积物的物质循环过程中占有重要地位。

[Objective] We studied the microbial diversity in the sediments of different depth in a gravity piston core HS-PC500 from Shenhu Area,the northern of South China Sea.[Methods] Total DNA was extracted from the sedimental materials;the archaeal and bacterial 16S rRNA gene sequences were amplified.The clone libraries were used to analyze the microbial systematic development.[Results] Group C3 was the predominant archaeal group in the top layer（0-5 cm bsf） sediments,and the Marine Benthic Group（MBG）-B group became predominant with depth,reaching 38.9% and 62.5% in the middle（350-355 cm bsf） and bottom（790-795 cm bsf） sediments.Some belonged to MBG-A,Miscellaneous Crenarchaeotic Group（MCG）,Thermoprotei,Novel Group Crenarchaeota（NGC）,Halobacteriales,MBG-E,South African Gold Mine Euryarchaeotic Group（SAGMEG）.Proteobacteria was the dominant bacterial group in the top of the core,but became minor deeper within the sediments.As depth increased,Chloroflexi and candidate division JS1 became the predominant groups and reached up to 28.1%,29.2% and 39%,24.7%.Other sequences respectively belonged to Nitrospirae,Actinobacteria,Acidobacteria,candidate division OP8,Spirochaetes,candidate division TM6,Deferribacteres and Plantomycete.[Conclusion] Down-core variation in microbial abundance in sediments of HS-PC500 was consistent with the changes of methane concentration in the same core;the lower microbial abundance might be probably due to lower total organic carbon（TOC） in sediments;However,microbial diversity was relatively high and community structure varied apparently with depth;the community was dominated by clusters that was dominated in sulfate reduction condition,suggesting that microbial metabolization played very important role in the material cycle of marine sediments.