Vestimentiferan tubeworms that thrive in deep-sea chemosynthetic ecosystems rely on a single species of sulfide-oxidizing gammaproteobacterial endosymbionts housed in a specialized symbiotic organ called trophosome as their primary carbon source. While this simple symbiosis is remarkably productive, the host-symbiont molecular interactions remain unelucidated. Here, we applied an approach for deep-sea in situ single-cell fixation in a cold-seep tubeworm, Paraescarpia echinospica . Single-cell RNA sequencing analysis and further molecular characterizations of both the trophosome and endosymbiont indicate that the tubeworm maintains two distinct metabolic “microniches” in the trophosome by controlling the availability of chemosynthetic gases and metabolites, resulting in oxygenated and hypoxic conditions. The endosymbionts in the oxygenated niche actively conduct autotrophic carbon fixation and are digested for nutrients, while those in the hypoxic niche conduct anaerobic denitrification, which helps the host remove ammonia waste. Our study provides insights into the molecular interactions between animals and their symbiotic microbes.

中文翻译：

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单细胞RNA-seq揭示深海化学合成管虫独特的代谢“微生态位”和密切的宿主-共生相互作用


在深海化学合成生态系统中繁衍生息的Vestimentiferan管虫依靠一种单一的硫化物氧化γ变形菌内共生体作为其主要碳源，该内共生体位于一种称为营养体的特殊共生器官中。虽然这种简单的共生关系非常有效，但宿主与共生体的分子相互作用仍不清楚。在这里，我们应用了一种在冷泉管虫中进行深海原位单细胞固定的方法，刺果副果。单细胞 RNA 测序分析以及营养体和内共生体的进一步分子表征表明，管虫通过控制化学合成气体和代谢物的可用性，在营养体中维持两个不同的代谢“微生态位”，从而导致含氧和缺氧条件。含氧生态位中的内共生体积极进行自养碳固定并消化营养物质，而缺氧生态位中的内共生体则进行厌氧反硝化，帮助宿主去除氨废物。我们的研究提供了对动物与其共生微生物之间分子相互作用的见解。