河口与热液区痕量金属与海洋细菌互作机制研究

Since trace metal clean sampling techniques were developed, the understanding of trace metals in the oceans have been revolutionized. Particularly, the iron hypothesis on the HNLC waters has been proposed in the 1970s, followed by a series of other key elements (e.g., Mo) which might also limit the growth of marine phytoplankton and bacteria. These studies demonstrate that trace metals play a key role in primary productivity in the ocean. Marine bacteria existed in the ocean widely, however there is still little information available regarding the involvement of trace metals in bacterial growth and metabolism relative to phytoplankton due to the fact that there is little natural waters specific for such studies. On the other hand, our previous investigation survey and bacterial cultures suggest that bacteria absorb, concentrate and speciate trace metals (including organic complexed fractions), which potentially impact phytoplankton and even the whole ecosystem. The project will choose two bacterially active sites with high levels of iron and molybdenum: the upper Pearl River estuary (low salinity anoxic estuarine zone, typical bacteria is Synochococcus) and shallow water hydrothermal vents near the Kueishan Island (Yellow and White smokers; typical bacteria is sulfur oxidizing bacteria). We will conduct field investigation along with manipulative laboratory cultures, and fully explore the interaction between trace metals (mainly including Fe and Mo) and bacteria, and the roles of these metals in the growth and N, S cycling of bacteria in these waters (Synochococcus and sulfur oxidizing bacteria). The project will enrich our understanding of the biogeochemistry of trace metals in the oceans, and facilitate new research topics in the fields of inorganic biology and paleoceanography.

铁钼等痕量金属钼构成生物酶活性中心，参与并影响海洋生物的碳氮硫代谢；细菌在海洋中广泛存在且丰度高，对海洋固碳、氮硫循环等过程发挥重要作用。然而，我们对海洋中铁钼与细菌的相互作用机制却缺乏认识。珠江口上游水域与龟山岛附近浅海热液都具有高钼铁特征，且分别以聚球菌与硫氧化菌为代表进行固碳、氮吸收或硫氧化，因而成为研究铁钼影响海洋细菌代谢的天然试验场。通过多年海洋观测与细菌培养研究，申请人提出关于铁钼与海洋细菌互作机制的科学新假设-海洋细菌是痕量金属的重要”富集器”与“加工厂”，即细菌吸收、储存，并转化金属形态(产生有机络合态)，从而影响海洋生态。基于此，本项目拟继续观测两大特色海区，并结合室内模拟，深入研究铁钼对典型细菌固碳及硫氧化等生态过程的作用，重点阐释细菌吸收、储存与转化痕量金属的过程与机制。本项目以痕量金属与海洋细菌互作的视角开展研究，有望为海洋痕量金属生物地球化学循环研究提供新思路。

为探讨痕量金属与细菌代谢的互作机制，本项目主要分为三个方面的工作，河口区调查；热液区调查，以及培养实验方面的室内培养研究。1）进行了全面的九龙江河口区的痕量金属调查，发现了主要的痕量金属分布规律，主要表现为：溶解态痕量金属随盐度增加逐渐被去除的趋势，而季节差异不大。与盐度的相关分析显示，溶解态痕量金属浓度变化受淡海水混合作用影响，同时也受海水稀释及颗粒物吸附沉降等影响。2）测定了水体的微型生物细胞体内的查生物代谢前体-蝶呤，主要用来指示细菌代谢过程。结果显示：生物蝶呤广泛存在于自然水体中，而生物蝶呤主要来源于水体中的微生物，不同种群的微生物体内生长所需的生物蝶呤也是大为不同的。通过对比叶绿素、AOU、盐度、温度等理化性质推测，自然水体中的生物蝶呤的含量可能受蓝藻类等微生物丰度影响。本研究也在台湾龟山岛热液区广泛发现了蝶呤，推测可能与细菌活动有关。.研究环非洲洋中脊深海热液与龟山岛浅海热液可培养异养微生物的多样性，分析发现两种热液环境中所分离的主要异养微生物群落组成类似，但浅海热液中所分离的异养微生物量更多且种类都更丰富。（2）通过16S rRNA高通量测序调查龟山岛热液系统中微生物的群落组成，发现沉积物与水体的微生物群落组成在统计学上存在明显差异，通过功能性宏基因组测序研究发现龟山岛热液系统存在硫氧化和碳固定的相关编码基因，以及有多种转运子，糖苷水解酶，肽酶的编码基因等。（3）对分别分离自龟山岛热液区的Maribacter sp. T28和南海近岸表层海水的Echinicola rosea JL3085这两株海洋拟杆菌进行基因组分析及多糖物质利用研究。.本项目调查了河口区与热液海域的金属与生物情况，通过分析细菌体内生源分子-蝶呤，发现了细菌代谢过程存在着明显的金属参与机制，对生物数据的深入分析，也找到了特殊细菌菌种及参与氮硫代谢过程的关键作用。

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