Metabolic control of dissolved organic matter dynamics

尽管溶解有机物质(DOM)是海水中最大的有机碳库，在海洋中的物质循环中发挥着关键作用，但人们对DOM在海水中动态变化的控制机制知之甚少。在本项目中，我们重点研究了DOM与海洋环境中微生物之间的相互作用，并对影响DOM细菌降解的因素进行了评价。新开发的方法使我们能够跟踪天然海水中蛋白质和其他生物聚合物的微生物呼吸(降解)。结果表明，与磷脂等其他生物聚合物相关的蛋白质比自由溶解的蛋白质更不容易降解。这些结果与最近发现的细菌膜蛋白和细胞壁物质大量积累在海洋中的发现一致，表明HMW-DOM的空间保护是DOM在海水中积累的重要机制。我们的数据对于理解DOM周转和模拟海洋中的DOM动态具有重要的意义。

Although dissolved organic matter (DOM) represents the largest reservoir of organic carbon in seawater and plays critical roles in material cycling within the oceans, little is known about mechanisms by which DOM dynamics is controlled in seawater. In this project, we focused on interactions between DOM and microbes in marine environments and evaluated the factors that affect bacterial degradation of DOM.A novel approach was developed to determine the degradation rate constant of dissolved proteins (an important component of DOM) by using radiolabeled bacterial proteins and peptidoglycan. The newly developed method allowed us to follow microbial respiration (degradation) of proteins and other biopolymers in natural seawater. Results demonstrated that the proteins associated with other biopolymers such as phospholipid are much less easily degradable than the proteins freely dissolved. These results are consistent with recent findings that bacterial membrane proteins and cell wall material largely accumulate in oceanic waters and suggest that the steric protection of HMW-DOM is an important mechanism by which DOM accumulates in seawater. Our data have important implications for understanding DOM turnover and modeling DOM dynamics in the oceans.