印度洋热液区赤杆菌水体垂直分布特征及其碳代谢特点研究

Aerobic anoxygenic photosynthetic heterotrophic bacteria (AAPB) play an important and unique role in global carbon cycle. Erythrobacter is an important group of AAPB and is widely distributed in marine environment. Ecology research about Erythrobacter was mainly focused on the upper water in the past years, but recently it was found that some members of Erythrobacter did not have function of photosynthesis and the highest abundance of Erythrobacter appeared at the depth of more than 200 m in the ocean. So we hypothesized that: (1) Erythrobacter can be divided into two functional groups: photosynthetic and non-photosynthetic groups. The true light layer is dominated by photosynthetic group, but non-photosynthetic group for the depth of 200 m or deeper. (2) Erythrobacter in the hydrothermal environment of the deep ocean of may have unique carbon metabolism characteristics. On the above two scientific hypothesizes, our subject focuses on the area of the hydrothermal environment of Indian Ocean and aims at : (1) exploring the characteristics of vertical distribution of Erythrobacter and its correlation with the environment, which will done by metagenomic data and genetic diversity research, combined with environmental factors. (2) isolating some representative photosynthetic Erythrobacter bacteria, clarifying their physiological characteristics, and further recognizing its carbon cycle pathway in the special hydrothermal environment of the deep ocean. Implementation of our project will help us have a comprehensive cognition of Erythrobacter in the role of the ocean carbon cycle, and will have important value for us to comprehensively understand its role in the process of global ocean carbon cycle and energy metabolism.

好氧不产氧光合异养细菌（AAPB）在全球碳循环中具有重要且独特作用。赤杆菌是AAPB的一个重要类群，广泛分布于海洋环境。过去主要针对上层水体赤杆菌开展生态学研究，然而近期研究发现，一些赤杆菌不具备光合作用能力，大洋赤杆菌丰度最高值往往出现在200m以深。我们假设：①赤杆菌分为光合和非光合两大功能类群，真光层以光合赤杆菌为主，以深通常以非光合赤杆菌为主；②深海热液生境中栖息的赤杆菌可能具有独特的碳代谢特点。针对上述科学假设，课题拟重点围绕印度洋热液区开展研究，通过宏基因组数据挖掘和基因多样性研究，并结合环境因子，探知赤杆菌分布特征及其与环境相关性；另一方面，分离赤杆菌代表株，阐明其生理学特征，认识深海热液特殊生境中的赤杆菌碳循环途径。课题实施将有助于加深对赤杆菌在大洋碳循环中作用的综合认知，对于全面认识其在全球海洋碳循环和能量代谢过程中的作用具有重要价值。

好氧不产氧光合细菌（Aerobic Anoxygenic Phototrophic Bacteria）是一类在有氧条件下具有光合作用功能的专性异养细菌，其生理生态特征独特，进化年代久远，在水生生态系统中广泛分布，在海洋碳循环中具有重要作用。赤杆菌被视为一类重要的AAPB，然而近期研究表明：部分赤杆菌不具备光合作用能力；深海热液口具有光辐射，为赤杆菌为代表的光合类群提供栖息环境。基于此，课题组提出2个科学假说：1）赤杆菌分为光合和非光合两大功能类群，光合类群主要存在于海洋真光层；2）深海热液环境中的赤杆菌光合类群可能具有独特的碳代谢特点。课题主要进展如下：1）基于基因组系统发育分析发现，光合类群处于一个稳定分支，将其归类为一个属，该属光合基因簇保守；2）16S rRNA基因扩增子分析显示，赤杆菌在真光层的平均丰度为0.88%，光合类群占比为68%，真光层以深的平均丰度为1.62%，光合类群占比为40%，结果表明，赤杆菌光合类群主要存在于海洋真光层；3）宏基因组分析发现，表层海水中光合基因的丰度（0.29-0.76%）显著高于沉积物（0.01-0.22%），深海沉积环境中存在光合基因，但丰度低；4）构建基于细菌叶绿素a和类胡萝卜素拉曼光谱检测方法，获得了具有光合类群特征峰的单细胞，分别属于赤杆菌光合类群及Sphingomonas属，基因注释显示，它们均含有光合基因及较多编码代谢氨基酸和无机离子的独有基因；5）设计了以柠檬酸钠和丙酮酸钠为碳源的改良培养基，赤杆菌可培养率可提高至4%，分离培养1株具有光合能力的菌株T40-3，该菌株具有光合基因簇，多相分类鉴定显示该菌株代表了红杆菌科的一个新属。.项目执行期间，发表或接收SCI期刊论文6篇，参编英文专著1章节，授权国家发明专利1件；项目主持人入选省部级人才项目，项目成员2人次晋升高级职称，2人次获得硕士学位。