Collaborative Research: Functional and genomic analysis of polysymbiosis in the wood-boring bivalve Lyrodus pedicellatus

每天都有大量的木材和木本植物材料进入海洋，为各种海洋生物提供了赖以生存的资源。 然而，人们对海洋木材所支持的生物群落知之甚少。 在全球范围内，海洋木材最重要的消费者是钻木双壳类的家庭Teredinidae（船蛆，主要发现在150米以上）和Pholadidae（亚科Xylophagainae，主要发现在深海，150-8000米）。 这些蛤依赖于细胞内的内共生细菌（内吞菌）来帮助它们消耗大多数其他动物不能利用的底物（木质纤维素）。 钻木双壳类的共生体有两种功能：1）产生酶以促进木质纤维素消化（木营养）和2）固氮（固氮）以补充宿主的缺氮饮食。 本研究的目的是利用分子生物学、生物化学和微生物学技术，探讨船虫共生性木质营养的生理生态学。在这项研究中，有三个问题是最重要的：1）在宿主种内和宿主种之间的共生体种群中发生了什么遗传变异？2)共生体对木质纤维素消化和固氮的贡献是多少？（3）在寄主和共生体之间营养物质和酶的转移涉及哪些物理和生化机制？

Each day massive quantities of wood and woody plant materials enter the oceans, providing resources upon which a large variety of marine organisms depend. However, the biological communities supported by marine wood are only poorly understood. Globally, the most important consumers of marine wood are wood-boring bivalves of the family Teredinidae (shipworms, primarily found above 150 m) and Pholadidae (subfamily Xylophagainae, primarily found in the deep sea, 150-8000 m). These clams depend on intracellular endosymbiotic bacteria (endocytobionts) to help them consume a substrate (lignocellulose) that cannot be utilized by most other animals. Two functions have been proposed for symbionts of wood-boring bivalves; 1) production of enzymes to facilitate lignocellulose digestion (xylotrophy) and 2) nitrogen fixation (diazotrophy) to supplement the host.s nitrogen-deficient diet. The purpose of the proposed research is to explore the physiological ecology of symbiotic xylotrophy in shipworms using molecular, biochemical and microbiological techniques. Three questions are foremost in this investigation; 1) What genetic variation occurs in symbiont populations within and between host species? 2) What is the quantitative contribution of symbionts to lignocellulose digestion and nitrogen fixation? and 3) What physical and biochemical mechanisms are involved in transfer of nutrients and enzymes between host and symbiont compartments?