Deep-sea Bathymodiolus mussels and their chemoautotrophic symbionts are well-studied representatives of mutualistic host-microbe associations. However, how host-symbiont interactions vary on the molecular level between related host and symbiont species remains unclear. Therefore, we compared the host and symbiont metaproteomes of Pacific B. thermophilus, hosting a thiotrophic symbiont, and Atlantic B. azoricus, containing two symbionts, a thiotroph and a methanotroph. We identified common strategies of metabolic support between hosts and symbionts, such as the oxidation of sulfide by the host, which provides a thiosulfate reservoir for the thiotrophic symbionts, and a cycling mechanism that could supply the host with symbiont-derived amino acids. However, expression levels of these processes differed substantially between both symbioses. Backed up by genomic comparisons, our results furthermore revealed an exceptionally large repertoire of attachment-related proteins in the B. thermophilus symbiont. These findings imply that host-microbe interactions can be quite variable, even between closely related systems.

中文翻译：

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相关共生贻贝物种的比较蛋白质组学揭示了宿主-共生体相互作用的高度可变性。

深海深海贻贝及其化学自养共生体是共生宿主-微生物协会的充分研究代表。然而，宿主 - 共生体相互作用如何在相关宿主和共生体物种之间的分子水平上变化仍不清楚。因此，我们比较了 Pacific B. thermophilus 的宿主和共生元蛋白质组，其中包含一个硫营养共生体，以及大西洋 B. azoricus，包含两个共生体，一个硫氧化菌和一个甲烷氧化菌。我们确定了宿主和共生体之间代谢支持的常见策略，例如宿主对硫化物的氧化，这为硫营养共生体提供了硫代硫酸盐储库，以及可以为宿主提供共生体衍生氨基酸的循环机制。然而，这些过程的表达水平在两种共生体之间存在显着差异。在基因组比较的支持下，我们的结果进一步揭示了嗜热芽孢杆菌共生体中异常大量的附着相关蛋白。这些发现意味着宿主-微生物的相互作用可能非常多变，即使在密切相关的系统之间也是如此。