How do shipworms eat wood? A non-enzymatic, symbiont-mediated mechanism for the digestion of lignocellulose in teredinids

船蛆生活在海洋中，与蛤有关。它们是世界上少数几种能吃木头的动物。它们还通过回收木材中的碳在自然界中发挥重要作用。据估计，世界上2 - 5%的木本植物材料被船蛆吃掉。这个项目的目标是了解船蛆是如何吃木头的。洋地黄的复杂结构并不容易。科学家们知道，相对较大的酶本身不能分解木材，因为木材分子挤得太紧，酶无法进入。船蛆在它们的鳃中养殖细菌，最近发现这些细菌产生非常小的化合物，这些化合物可能会进入船蛆的肠道，在那里这些小化合物可以产生强大的氧自由基来消化木材。制造氧自由基被认为是将木材结构分解成更小碎片所需的第一步。然后，在第二步中，酶可以完全消化木材。以前，可以产生氧自由基的化合物只在某些类型的真菌中发现，这些真菌也会消化木材。科学家们认为，研究这种船蛆化学可能会开辟有关碳如何在我们的海洋中循环的新知识，也可能导致制造生物燃料和可再生材料的新发现。参与该项目的研究人员也坚信支持年轻的、代表性不足的女性科学家，并将在当地城镇为女孩提供教育机会。船蛆是世界海洋中木质纤维素的主要降解者;它们对木制结构（船只、码头和海防）造成数十亿美元的破坏，但它们也在碳循环中发挥重要作用。它们的共生群落相对简单，它们的消化系统独特的区室化，使船蛆共生成为陆地木营养生物的一个容易对付的对手（例如，真菌、白蚁）。该项目的目标是通过检查这些动物如何与其鳃内共生体相互作用，并具体确定共生体介导的化学降解机制是否在宿主肠道中活跃，来探索船蛆木材消化的未知机制。实现这一目标有三种方法。第一种方法是确定如何低分子量（LMW）的代谢产物从船蛆鳃共生体可能被激活在宿主肠道中产生的非酶系统的木质纤维素解构。这涉及绘制低分子量物质代谢物在鳃和消化系统中的位置。第二种方法将研究pH环境的肠道区室化，这可能促进共生体介导的铁还原、氧化还原循环以及与CMF反应相关的羟基自由基的产生。它还将评估的空间布局和划分的船蛆解剖，并确定和映射结构连接鳃内共生体与消化道。第三种方法将比较和分析在同位素标记的木材上生长的船蛆的消化产物和废物。了解木材消化的基础可能有助于发现候选催化/酶系统，并为生物基材料和生物燃料生产开发新的战略。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Shipworms live in the ocean and are related to clams. They are some of a very few animals in the world that can eat wood. They also play an important role in nature by recycling the carbon in wood. It is estimated that between 2 - 5% of the world’s woody plant material is eaten by shipworms. The goal of this project is to understand how shipworms eat wood. Digesting wood’s complex structure isn’t easy. Scientists know that relatively large enzymes alone cannot break down wood, because wood molecules are packed too tightly together for enzymes to enter. Shipworms farm bacteria in their gills, and these bacteria have recently been found to produce very small compounds that may move into the shipworm gut where the small compounds can make powerful oxygen radicals to digest the wood. Making the oxygen radicals is proposed as the first step needed to break open the wood structure into smaller pieces. Then, in a second step, enzymes can completely digest the wood. Previously, the compounds that can make the oxygen radicals were found only in some types of fungi that also digest wood. Scientists believe that studying this shipworm chemistry may open up new knowledge about how carbon is cycled in our oceans, and may also lead to new discoveries on ways to make biofuels and renewable materials. The researchers involved in this project also believe strongly in supporting young, underrepresented female scientists and will be running educational opportunities for girls in a local town.Shipworms are the principle degraders of lignocellulose across the world’s oceans; they cause billions of dollars of damage to wooden structures (boats, piers and sea-defenses), but they also play a major role in carbon-cycling. The relative simplicity of their symbiotic communities and the unique compartmentalization of their digestive system make shipworm symbiosis a tractable counterpoint to terrestrial xylotrophs (e.g., fungi, termites). The goal of this project is to explore the unknown mechanisms of wood digestion in shipworms by examining how these animals interact with their gill endosymbionts and determining specifically whether a symbiont-mediated chemical degradation mechanism is active in the host gut. There are three approaches to reach this goal. The first approach is to determine how low molecular-weight (LMW) metabolites from shipworm gill symbionts may be activated in the host gut to generate a non-enzymatic system for lignocellulose deconstruction. This involves mapping the location of LMW metabolites in the gill and digestive system. The second approach will examine gut compartmentalization for pH environments that may promote symbiont-mediated iron reduction, redox-cycling and the generation of hydroxyl radicals associated with CMF reactions. It will also assess the spatial arrangement and compartmentalization of shipworm anatomy, and identify and map structures linking the gill endosymbionts with the digestive tract. The third approach will compare and analyze the digestive products and waste material from shipworms grown on isotopically-labelled wood. Understanding the basis of wood digestion may allow discovery of candidate catalytic/enzymatic systems and development of new strategies for bio-based materials and biofuel production.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.