Molecular Mechanisms of Marine Polysaccharide Depolymerization and Metabolism

据估计，海洋植物生物量[即微藻和大藻（海藻）]仅为陆地植物生物量的约1/200。事实上，光合作用过程中吸收的大部分碳都在陆地植物中。然而，海洋中光合作用固定碳的年周转率（每次总质量）与陆地大致相等，表明这是一个高度动态的过程，其标准化的再循环率是陆地的数百倍。在海洋和陆地环境中，这种碳主要以被称为多糖的糖链的形式锁定。陆生植物多糖的微生物降解，纤维素是主要的例子，已经被深入研究了50多年，因此对它的理解相对较好；海洋藻类多糖的情况并非如此。海藻中的多糖由一组复合糖组成，其化学性质与陆生植物不同。因此，推动这项研究计划的愿景是识别和定义使细菌能够代谢海洋多糖的独特代谢系统的大部分未经研究的分子特征。******确定光合作用固定碳如何在海洋中循环是理解全球碳循环的基本目标的基础。然而，在我们这个气候变化的世界里，可再生资源、碳中和足迹和替代燃料的承诺越来越有吸引力。海藻是一种极具吸引力的碳水化合物含量高的可再生资源。拟议的研究计划正在产生一个知识平台，可以用来设计将这种生物质转化为可发酵糖的策略，然后这些糖可以转化为生物燃料或其他有用的生物产品。此外，许多海洋多糖被用于食品、化妆品、农业和潜在的医学治疗。这项研究提供了一套新的工具来酶修饰这些聚合物，以潜在地控制它们在这些应用中的性能。最后，这项工作也为人类和动物肠道中细菌的代谢能力提供了新的见解，在那里它们帮助消化膳食中的海洋多糖。这个创新的研究项目是加拿大同类项目中唯一的一个，有可能改变一个具有显著广泛影响的领域。*****

Ocean plant biomass [i.e. microalgae and macroalgae (seaweed)] is estimated to be only ~1/200 that of terrestrial plant biomass. Indeed, most of the carbon incorporated by photosynthetic processes is in land plants. However, the annual turnover rate (total mass per time) of photosynthetically fixed carbon in the oceans is roughly equal to that on land, indicating a highly dynamic process with a normalized rate of recycling that is hundreds of times greater than on land. In both the marine and land environments this carbon is locked primarily in the form of sugar chains called polysaccharides. The microbial degradation of terrestrial plant polysaccharides, cellulose being the major example, has been intensely studied for over 50 years and it is therefore relatively well understood; the same is not true of marine algal polysaccharides. The polysaccharides present in seaweed comprise a group of complex sugars that are chemically different from those of terrestrial plants. The vision that drives this research program, therefore, is to identify and define the largely unexamined molecular features of the unique metabolic systems that enable bacteria to metabolize marine polysaccharides.******Determining how photosynthetically fixed carbon is recycled in our oceans is fundamental to the basic goal of understanding the global carbon cycle. However, in our world of climate change, the promises of renewable resources, carbon neutral footprints, and alternative fuel sources are increasingly attractive. Marine algae are an extremely appealing renewable resource with a high carbohydrate content. The proposed research program is generating a knowledge platform that can be leveraged to design strategies for the conversion of this biomass into fermentable sugars, which could then be converted into biofuels or other useful bioproducts. Additionally, many marine polysaccharides are used in foods, cosmetics, agriculture, and potential medical therapeutics. This research is providing a new set of tools to enzymatically modify these polymers to potentially control their properties in these applications. Finally, this work is also providing novel insights into the metabolic capabilities of the bacteria that inhabit human and animal guts where they aid digestion of dietary marine polysaccharides. This innovative research program, which is the only one of its kind in Canada, has the potential to transform a field that has a remarkably wide impact.*****