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冲绳海槽和马努斯海盆热液区沉积物微生物群落的结构与代谢研究
王海亮
学位类型博士
导师孙黎
2017-05-22
学位授予单位中国科学院大学
学位授予地点北京
学位专业海洋生物学
关键词冲绳海槽 马努斯海盆 沉积物 宏基因组 微生物多样性
摘要深海热液环境是地球上天然的极端环境之一,孕育着活跃的生态系统。深海热液环境被认为可能是地球上生命起源和早期进化的地点,吸引着来自不同领域的科学家们的目光。冲绳海槽和马努斯海盆是西太平洋中正在活动的典型的弧后盆地,科学家们在这两个地区的地质环境和热液地球化学性质方面已经有了深入的研究,但在热液区沉积物微生物生态系统方面的研究甚少。中国“科学号”海洋科学综合考察船对冲绳海槽中段的伊平屋北、伊平屋脊热液区和东马努斯海盆的Pacmanus、Desmos热液区进行了科学考察,采集了深海沉积物样品,为深海热液微生物生态系统的研究提供了宝贵的材料。本研究论文对“科学号”两次科考采集的八份沉积物样品进行了研究,分析了沉积物微生物群落的组成、代谢和运行的能量来源,试图揭示微生物深海热液环境的适应机制。
本论文的研究结果表明,伊平屋北、伊平屋脊、Pacmanus和Desmos热液区沉积物微生物群落具有很高的微生物多样性。在微生物组成方面,均以细菌为主,古菌的丰度明显低于细菌的丰度。变形菌是微生物群落中最具优势的菌群,尤其是α-和γ-变形菌纲。广古菌门是伊平屋北和伊平屋脊热液区微生物群落的主要古菌类群,是甲烷代谢的重要参与者;奇古菌门是Pacmanus和Desmos热液区微生物群落的主要古菌类群,参与氨氧化过程。化能自养微生物是群落的初级生产者,其重要成员包括氨氧化细菌、氨氧化古菌、亚硝酸盐氧化菌、硫氧化菌和产甲烷古菌等,它们利用多种碳固定途径同化CO2,制造有机物。
环境中的NH4+、NO2-、H2和还原性硫化物等是冲绳海槽和东马努斯海盆热液区沉积物微生物群落运行的能量来源,而甲烷仅是伊平屋热液区微生物潜在的能源物质。在伊平屋热液区沉积物微生物群落中发现了厌氧甲烷氧化古菌和细菌,它们分别可以通过硝酸盐还原耦联的反向产甲烷途径和“intra-aerobic denitrification”途径利用甲烷。在八个微生物群落中,硝化作用和反硝化作用是微生物群落的主要氮代谢过程,硫酸盐还原和硫化物反向硫酸盐还原的氧化过程是主要的硫代谢过程。NO3-和SO42-是微生物所利用的重要电子受体。
本论文针对伊平屋北和伊平屋脊热液区沉积物样品,分析了微生物群落形成和运行的机制。借鉴海洋沉积物早期成岩模型,结合本研究在微生物群落代谢方面的分析结果,我们认为:有机物降解产生的小分子物质促进了微生物群落的形成,甲烷代谢是微生物群落运行的一种驱动力,促进了碳、氮和硫元素在群落内的循环;在沉积物深度剖面上,微生物分层分布,以处理微生物对氧和营养盐的需求、底物抑制效应和微生物间的互利关系。
此外,我们还探究了深海微生物对沉积物环境的潜在适应机制。DNA修复系统是深海热液微生物的一种生存机制,微生物利用DNA修复系统修复极端环境对基因组造成的损伤,从而维持核酸结构的稳定。微生物还可改变细胞膜中心磷脂和磷脂酰甘油的比例,通过多种ABC转运系统、阳离子/H+反向转运系统和机械敏感性离子通道调控胞内多胺、Na+、K+以及渗透压调节剂 (如甜菜碱、脯氨酸和海藻糖) 的含量,从而维持细胞的渗透压和pH稳态。
本论文在伊平屋北、伊平屋脊、Pacmanus和Desmos热液区沉积物微生物生态系统的诸多研究发现均属首次。本研究的结果有助于我们理解深海微生物群落形成和运行的机制,揭示深海微生物的热液环境适应机制,加深我们对深海热液生态系统的认识。
其他摘要Deep-sea hydrothermal environment is one of natural extreme environments on Earth. However, it harbors active ecosystems. Submarine hydrothermal environments have been considered as a possible site for the origin and early evolution of life on Earth. Hydrothermal systems attract the attentions of scientists from different research fields. Okinawa Trough and Manus Basin, both located in the western Pacific Ocean, are two typical back-arc basins, which are active in different expansion phases. Although previous studies have provided insights into the geological settings and geochemistry of hydrothermal fluids in the two regions, little is known about the microbial ecosystems inhabiting the sediments from the hydrothermal fields. Hydrothermal field investigations were conducted by the scientific research vessel “KEXUE” in Iheya North and Iheya Ridge of mid-Okinawa Trough and in Pacmanus and Desmos of eastern Manus Basin. Deep-sea sediment samples were collected during the two cruises, which provide us precious materials for the research of submarine hydrothermal microbial ecosystems. Eight sediment samples were used in the current study, and taxonomic compositions, metabolic profiles and potential energy sources of microbial communities were analyzed, aiming to illustrate microbial adaptation strategies to deep-sea hydrothermal environments.
The results showed that there were high microbial diversities in the microbial communities inhabiting the sediments of Iheya North, Iheya Ridge, Pacmanus and Desmos hydrothermal fields. All the microbial communities were dominated by bacteria and, to a lesser extent, archaea. Proteobacteria, especially Alpha- and Gammaproteobacteria, were the dominant bacterial populations in these microbial communities. Euryarchaeota was the dominant archaeal population in the microbial communities from Iheya North and Iheya Ridge, which was an important participant in methane metabolism; Thaumarchaeota, involved in ammonia oxidization, was the predominant archaeal population in the microbial communities from Pacmanus and Desmos. Chemolithoautotrophic microorganisms were primary producers in all the microbial communities. The important members of the autotrophs included ammonia-oxidizing bacteria and archaea, nitrite oxidizer, sulfur oxidizer and methanogens, which can assimilate CO2 via various carbon fixation pathways thereby producing organic matters.
Ammonia, nitrite, hydrogen and reduced sulfur compounds as important energy sources fueled the microbial communities in the sediment habitats of mid-Okinawa Trough and eastern Manus Basin. Methane was a potential energy source for microorganisms inhabiting Iheya hydrothermal fields; anaerobic methane-oxidizing archaea and bacteria, likely oxidizing methane through reverse methanogenesis coupled to nitrate reduction and “intra-aerobic denitrification” respectively, were found in the communities. In the eight microbial communities, nitrification and denitrification were primary nitrogen metabolic processes, and sulfate reduction and sulfur-oxidizing reverse sulfate reduction were primary sulfur metabolic processes. Nitrate and sulfate as important electron acceptors were utilized by microorganisms.
In this study, taking samples of Iheya North and Iheya Ridge hydrothermal fields as an example, we tried to illustrate how the microbial communities constructed and operated in deep-sea sediments. An assumption was made on the basis of metabolic profiles of the microbial communities as revealed by metagenomics in this study and a reference model of early diagenetic process in marine sediments. We think that small molecules which originated from the decomposition of organic matters promoted the formation of microbial communities and that methane metabolism as a power drove the carbon, nitrogen and sulfur cycling and the ecosystem operation. The microorganisms in the microbial communities were predicted to distribute in different sediment layers to deal with the needs for oxygen and nutrients, substrate inhibition, and microbial consortium.
This study contributed to shed light on microbial adaptation strategies to deep-sea sedimental environments. DNA repair system represented a survival mechanism for submarine microorganisms, which could cope with the damaging effects on the genomes caused by the harsh environments, thereby maintaining microbial primary structures of nucleic acids. In addition, there were other microbial adaptation strategies to regulate osmoadaptation and pH homeostasis, such as changing the contents of cardiolipin and phosphatidylglycerol in membrane lipids, controlling the concentrations of polyamines, Na+, K+ and osmoprotectants (e.g., glycine betaine, proline, trehalose) via various ABC-transporting systems, cation:proton antiporters and mechanosensitive channels.
Many findings in this study are for the first time among the relevant researches about microbial ecosystems in the sediment habitats surrounding Iheya North, Iheya Ridge, Pacmanus and Desmos hydrothermal fields. The results of this study facilitate our understanding the formation and operation of submarine microbial communities, unveil the adaptation mechanisms of deep-sea microorganisms, and add insights into the recognition of deep-sea hydrothermal ecosystems.
学科领域微生物学
语种中文
文献类型学位论文
条目标识符http://ir.qdio.ac.cn/handle/337002/136624
专题实验海洋生物学重点实验室
作者单位中国科学院海洋研究所
推荐引用方式
GB/T 7714
王海亮. 冲绳海槽和马努斯海盆热液区沉积物微生物群落的结构与代谢研究[D]. 北京. 中国科学院大学,2017.
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