Heterotrophic CO₂ fixation is a significant yet underappreciated CO₂ flux in environmental carbon cycling. In contrast to photosynthesis and chemolithoautotrophy – the main recognized autotrophic CO₂ fixation pathways – the importance of heterotrophic CO₂ fixation remains enigmatic. All heterotrophs – from microorganisms to humans – take up CO₂ and incorporate it into their biomass. Depending on the availability and quality of growth substrates, and drivers such as the CO₂ partial pressure, heterotrophic CO₂ fixation contributes at least 1 %–5 % and in the case of methanotrophs up to 50 % of the carbon biomass. Assuming a standing stock of global heterotrophic biomass of 47–85 Pg C, we roughly estimate that up to 5 Pg C might be derived from heterotrophic CO₂ fixation, and up to 12 Pg C yr⁻¹ originating from heterotrophic CO₂ fixation is funneled into the global annual heterotrophic production of 34–245 Pg C yr⁻¹. These first estimates on the importance of heterotrophic fixation of inorganic carbon indicate that this pathway should be incorporated in present and future carbon cycling budgets.

中文翻译：

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综述与综合：无机碳的异养固定——环境碳循环中显着但不可见的通量

异养 CO ₂固定是环境碳循环中重要但未被充分认识的 CO ₂通量。与光合作用和化学自养（主要公认的自养 CO ₂ 固定途径）相反，异养 CO ₂固定的重要性仍然是个谜。所有异养生物——从微生物到人类——都会吸收 CO ₂并将其融入其生物质中。取决于生长底物的可用性和质量，以及 CO ₂分压、异养 CO ₂等驱动因素固定贡献至少 1%–5%，在甲烷氧化菌的情况下，高达 50% 的碳生物量。假设全球异养生物量的常备库存为 47-85 Pg C，我们粗略估计高达 5 Pg C 可能来自异养 CO ₂固定，而高达 12 Pg C yr ^-1来自异养 CO ₂固定是漏斗进入全球年异养产量 34-245 Pg C yr ^-1。这些对无机碳异养固定重要性的初步估计表明，该途径应纳入当前和未来的碳循环预算。