Ammonium‐oxidizing chemoautotrophic members of Thaumarchaea are proposed to be the key players in the assimilation of bicarbonate in the dark (ABD). However, this process may also involve heterotrophic metabolic pathways, such as fixation of carbon dioxide (CO₂) via various anaplerotic reactions. We collected samples from the depth of 4900 m at the Matapan‐Vavilov Deep (MVD) station (Hellenic Trench, Eastern Mediterranean) and used the multiphasic approach to study the ABD mediators in this deep‐sea ecosystem. At this depth, our analysis indicated the occurrence of actively CO₂‐fixing heterotrophic microbial assemblages dominated by Gammaproteobacteria with virtually no Thaumarchaea present. [¹⁴C]‐bicarbonate incorporation experiments combined with shotgun [¹⁴C]‐proteomic analysis identified a series of proteins of gammaproteobacterial origin. More than quarter of them were closely related with Alteromonas macleodii ‘deep ecotype’ AltDE, the predominant organism in the microbial community of MVD. The present study demonstrated that in the aphotic/hadal zone of the Mediterranean Sea, the assimilation of bicarbonate is associated with both chemolithoauto‐ and heterotrophic ABD. In some deep‐sea areas, the latter may predominantly contribute to the de novo synthesis of organic carbon which points at the important and yet underestimated role heterotrophic bacterial populations can play the in global carbon cycle/sink in the ocean interior.

中文翻译：

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异养碳酸氢盐的同化作用是希腊海沟海底区（地中海最深处）从头合成有机碳的主要过程。

氨氧化的自养会员牛逼haumarchaea提出要在碳酸氢盐的黑暗（ABD）同化的关键球员。但是，该过程也可能涉及异养代谢途径，例如通过各种过氧化物反应固定二氧化碳（CO ₂）。我们在Matapan-Vavilov Deep（MVD）站（地中海东部的希腊海沟）采集了4900 m深度的样本，并使用多相方法研究了该深海生态系统中的ABD介体。在这个深度，我们的分析表明，积极地发生CO ₂ -定影由主导异养微生物组合ģ ammaproteobacteria几乎没有Ť haumarchaea当下。[ ¹⁴ C]-碳酸氢盐掺入实验与shot弹枪[ ¹⁴ C]-蛋白质组学分析相结合，鉴定出了一系列源自丙型细菌的蛋白质。其中有超过四分之一与MVD微生物群落中的主要有机体-苹果异形菌“深生态型” AltDE密切相关。本研究表明，在地中海的无水/哈德地区，碳酸氢盐的同化与化石自养和异养ABD都有关系。在某些深海地区，后者可能主要是造成了新生 有机碳的合成指出了异养细菌种群的重要但被低估的作用，可以在海洋内部的全球碳循环/汇中发挥作用。