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，为大量海洋生物提供赖以生存的资源。然而，对海洋木材支持的生物群落了解甚少。在全球范围内，海洋木材最重要的消费者是Teredinidae科的蛀木双壳类（船虫，主要发现于150米以上）和Pholadidae （Xylophagainae亚科，主要发现于150-8000米的深海）。这些蛤蜊依靠细胞内共生细菌（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）。对钻孔双壳类共生体提出了两种功能；1)产生促进木质纤维素消化的酶（xylotrophy）和2)固氮（重氮trophy）来补充宿主。氮缺乏饮食。本研究旨在利用分子生物学、生物化学和微生物学等技术，探讨船虫共生木质素的生理生态学。在这项调查中，有三个问题是最重要的；1)寄主物种内部和寄主物种之间的共生体种群发生了哪些遗传变异？2)共生体对木质纤维素消化和固氮的定量贡献是什么？3)寄主和共生体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?