在寡营养海洋环境中，多个异养细菌类群可以诱导表达磷脂酶PlcP基因将细胞膜磷脂替换为不含磷的脂类，以降低细胞对外界有机磷的需求来适应海洋极端环境，且PlcP具有多样性。但是，PlcP参与海洋细菌膜脂代谢的分子机制及其在海洋细菌膜脂等有机碳磷循环中的作用到目前为止还不清楚。本项目拟通过选取三大类群（α-变形菌纲、γ-变形菌纲和拟杆菌纲）代表性PlcP序列研究PlcP的降解机制及其在海洋碳磷循环中的作用。首先，研究PlcP的磷脂酶活性及酶学性质，揭示不同类群PlcP的催化特性。其次，通过结构、突变和生化分析，阐明不同类群PlcP降解磷脂底物的分子机制。最后，通过比较不同类群PlcP的催化特性及机制，结合来源菌的膜脂组分等生理特征并联系菌株在海洋环境中的生态分布情况，揭示磷脂酶PlcP在海洋细菌膜脂高分子量有机碳和有机磷循环中的作用。研究结果将为阐明海洋微生物驱动碳磷元素循环的机制提供重要依据。

In the oligotrophic marine environments, phylogenetically diverse heterotrophic bacteria can be induced to express the gene PlcP encoding-phospholipase to replace cellular phospholipids with membrane lipids devoid of P, which facilitate survival of bacteria in marine extreme conditions. Different bacteria can produce different types of PlcP. Until now, the molecular mechanism for PlcP involved in membrane lipid metabolism of marine microorganisms and the role of PlcP in marine carbon and phosphorus cycles is still unclear. This project intends to study representative members (PhPlcP, PsPlcP and DoPlcP) of three major groups of PlcP to illustrate the catalytic mechanisms of these PlcP proteins and their potential role in marine carbon and phosphorus cycles. The phospholipase activities of PhPlcP, PsPlcP and DoPlcP will be biochemically characterized. Structural analysis in combination with mutational and biochemical analysis will reveal the catalytic mechanisms of PhPlcP, PsPlcP and DoPlcP against phospholipids, respectively. To reveal the potential role of PlcP phospholipases in marine carbon and phosphorus cycles, the catalytic properties and catalytic mechanisms of PhPlcP, PsPlcP and DoPlcP will be compared, the membrane lipid composition of strains producing them will be analyzed, and the distribution and the abundace of PlcP homologs and bacterial strains producing them in marine environments will also be analyzed. Our results in this project will provide important basis for illustrating the mechanism for marine carbon and phosphorus cycles driven by marine microorganisms.