Anoxic marine zones (AMZs), also known as ‘oxygen‐deficient zones’, contribute to the loss of fixed nitrogen from the ocean by anaerobic microbial processes. While these microbial processes associated with the nitrogen cycle have been extensively studied, those linked to the carbon cycle in AMZs have received much less attention, particularly the autotrophic carbon fixation — a crucial component of the carbon cycle. Using metagenomic and metatranscriptomic data from major AMZs, we report an explicit partitioning of the marker genes associated with different autotrophic carbon fixation pathways along the redox gradient (from oxic to anoxic conditions) present in the water column of AMZs. Sequences related to the Calvin‐Benson‐Bassham cycle were found along the entire gradient, while those related to the reductive Acetyl‐CoA pathway were restricted to suboxic and anoxic waters. Sequences putatively associated with the 3‐hydroxypropionate/4‐hydroxybutyrate cycle dominated in the upper and lower oxyclines. Genes related to the reductive tricarboxylic acid cycle were represented from dysoxic to anoxic waters. The taxonomic affiliation of the sequences is consistent with the presence of microorganisms involved in crucial steps of biogeochemical cycles in AMZs, such as the gamma‐proteobacteria sulfur oxidisers, the anammox bacteria Candidatus Scalindua and the thaumarcheota ammonia oxidisers of the Marine Group I.

中文翻译：

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在缺氧的海洋水中沿着氧化还原梯度的自养碳固定途径。

缺氧海洋区（AMZs），也称为“缺氧区”，通过厌氧微生物过程导致海洋中固定氮的损失。尽管已经广泛研究了与氮循环相关的这些微生物过程，但与AMZ中碳循环有关的微生物过程受到的关注却少得多，尤其是自养碳固定-碳循环的关键组成部分。使用来自主要AMZ的宏基因组学和元转录组学数据，我们报告了与AMZs水柱中存在的氧化还原梯度（从有氧到无氧条件）不同的自养碳固定途径相关的标记基因的明确划分。沿着整个梯度发现了与Calvin-Benson-Bassham循环有关的序列，而与还原性乙酰辅酶A途径有关的那些仅限于低氧和缺氧水域。推定的与3-羟基丙酸酯/ 4-羟基丁酸酯循环相关的序列在上部和下部羟丙基中占主导地位。从还原性缺氧到缺氧性水代表了与还原性三羧酸循环有关的基因。序列的分类学隶属关系与AMZs中生物地球化学循环关键步骤中涉及的微生物的存在相一致，例如γ-变形杆菌硫氧化剂，厌氧氨氧化菌海洋集团I的假丝酵母（Candidatus Scalindua）和thaumarcheota氨氧化剂。