海洋细菌驱动重要有机氮氧化三甲胺（TMAO）生物地球化学循环的生化过程与分子机制

氧化三甲胺（TMAO）是海洋有机氮循环的重要载体物质。玫瑰杆菌（Roseobacter）是海洋中代谢TMAO的重要细菌类群，能够代谢TMAO产生易挥发性的甲基胺类物质，这些物质可以进入大气层并参与云的形成，从而对全球气候产生影响。目前海洋细菌吸收代谢TMAO的分子机制还不清楚。本项目综合运用微生物生理学、生物化学、结构生物学、酶学等技术，开展如下研究：首先，解析Roseobacter中TMAO转运系统的结构，揭示其转运TMAO的分子机制；其次，解析TMAO胞内代谢通路中关键酶的结构，揭示海洋细菌胞内代谢TMAO的分子机制；最后，通过测定TMAO代谢过程中各种酶的动力学参数，以及各个酶在TMAO等底物诱导情况下的转录表达水平，结合遗传学证据，阐明海洋细菌代谢TMAO的调控机制。研究结果将揭示海洋Roseobacter驱动TMAO生物地球化学循环的生化过程及分子机制，具有重要的理论意义。

TMAO（Trimethylamine N-oxide）is an important participant in global nitrogen cycle. Marine Roseobacter clade is an important bacterial group that metabolizes TMAO into volatile methylated amines. When released into the atmosphere through air-sea flux, these methylated amines can participate in forming cloud condensation nuclei that may influence the global weather and climate. However, the molecular mechanisms of many enzymes involved in TMAO metabolism are still unclarified. In this program, we will (1) solve the structure of TMAO transporter from Roseobacter and study the transport mechanism of TMAO, (2) solve the structures of key enzymes involved in TMAO metabolism pathway and reveal the molecular mechanism of intracellular TMAO metabolism in Roseobacter, and (3) determine the kinetic parameters of the key enzymes and the expression level of these enzymes under TMAO induction and reveal the regulation mechanism of TMAO metabolism with genetic evidence. The results of this program will uncover the biochemical progress and molecular mechanism of TMAO biogeochemical cycling driven by Roseobacter, which have important theoretical significance.