大洋表层海水中富营养细菌与寡营养细菌共存与互作机制：以Pseudoalteromonas属和Brachybacterium属菌株为例

大洋表层海水大多为寡营养环境，但依然生存着大量微生物，包括高丰度自养蓝藻和异养寡营养细菌、低丰度富营养细菌、低等浮游动物及病毒，其中富营养细菌与异养寡营养细菌共存与相互作用，在驱动高分子量（HMW）有机质的生物地球化学循环过程中发挥重要作用。但至今，有关大洋富营养细菌和寡营养细菌共存和相互作用的过程与机制尚未被阐明。本项目首先建立富营养细菌和寡营养细菌相互作用与共存的实验室研究体系，发现和验证大洋富营养细菌和寡营养细菌共存和相互作用现象及其特征。此后进一步揭示大洋富营养细菌和寡营养细菌相互作用驱动HMW有机氮循环的过程及其机制。最后系统阐明大洋富营养细菌和寡营养细菌对不同浓度有机氮生态位的适应及其机制，最终揭示大洋寡营养海水中富营养菌和寡营养菌的共存机制。该研究将为全面阐述大洋微生物群落驱动高分子量有机质生物地球化学循环过程与机制提供重要依据，具有重要理论意义。

Oceanic surface seawater mostly represents oligotrophic environment, where there still exists a large number of microorganisms, including autotrophic cyanobacteria and heterotrophic oligotrophic bacteria with high abundance, copiotrophic bacteria with low abundance, zooplanktons and viruses. Among them, copiotrophic bacteria coexist and interact with heterotrophic oligotrophic bacteria, which play important roles in driving the biogeochemical cycle of the high molecular weight (HMW) organic matter. But up to now, the process and mechanism of coexistence and interaction between oceanic copiotrophic bacteria and oceanic oligotrophic bacteria have not been elucidated. This project will firstly establish a laboratory research system for the interaction and coexistence of copiotrophic bacteria and oligotrophic bacteria to discover and verify the phenomena and characteristics of the coexistence and interaction of oceanic copiotrophic bacteria and oceanic oligotrophic bacteria. Thereafter, the process and mechanism of interaction between oceanic copiotrophic bacteria and oceanic oligotrophic bacteria to drive the HMW organic nitrogen cycling will be further revealed. Finally, the adaptation of oceanic copiotrophic bacteria and oceanic oligotrophic bacteria to niches of different concentrations of organic nitrogen and its mechanism will be systematically elucidated and the coexistence mechanism of copiotrophic bacteria and oligotrophic bacteria in oceanic oligotrophic seawater will be revealed. This study will provide important basis for comprehensively elaborating the process and mechanism of oceanic microbial communities to drive the biogeochemical cycling of the HMW organic matter and has important theoretical significance.