Bacillus subtilis endospore‐mediated forsterite dissolution experiments were performed to assess the effects of cell surface reactivity on Mg isotope fractionation during chemical weathering. Endospores present a unique opportunity to study the isolated impact of cell surface reactivity because they exhibit extremely low metabolic activity. In abiotic control assays, ²⁴Mg was preferentially released into solution during forsterite dissolution, producing an isotopically light liquid phase (δ²⁶Mg = −0.39 ± 0.06 to −0.26 ± 0.09‰) relative to the initial mineral composition (δ²⁶Mg = −0.24 ± 0.03‰). The presence of endospores did not have an apparent effect on Mg isotope fractionation associated with the release of Mg from the solid into the aqueous phase. However, the endospore surfaces preferentially adsorbed ²⁴Mg from the dissolution products, which resulted in relatively heavy aqueous Mg isotope compositions. These aqueous Mg isotope compositions increased proportional to the fraction of dissolved Mg that was adsorbed, with the highest measured δ²⁶Mg (−0.08 ± 0.07‰) corresponding to the highest degree of adsorption (~76%). The Mg isotope composition of the adsorbed fraction was correspondingly light, at an average δ²⁶Mg of −0.49‰. Secondary mineral precipitation and Mg adsorption onto secondary minerals had a minimal effect on Mg isotopes at these experimental conditions. Results demonstrate the isolated effects of cell surface reactivity on Mg isotope fractionation separate from other common biological processes, such as metabolism and organic acid production. With further study, Mg isotopes could be used to elucidate the role of the biosphere on Mg cycling in the environment.

中文翻译：

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镁同位素分馏过程中微生物增强了镁橄榄石的溶解。

进行了枯草芽孢杆菌内生孢子介导的镁橄榄石溶出实验，以评估化学风化过程中细胞表面反应性对镁同位素分馏的影响。内生孢子为研究细胞表面反应性的孤立影响提供了独特的机会，因为它们表现出极低的代谢活性。在非生物控制实验，²⁴的Mg被优先镁橄榄石溶解期间释放到溶液中，产生的同位素轻液相（δ ²⁶的Mg = -0.39±0.06 -0.26至±0.09‰）相对于初始矿物组合物（δ ²⁶Mg ＝ -0.24±0.03‰）。内生孢子的存在对Mg同位素分馏没有明显影响，而Mg同位素分馏与Mg从固体释放到水相中有关。但是，内生孢子表面优先从溶解产物中吸附²⁴ Mg，这导致Mg同位素水溶液相对较重。这些水性镁同位素组合物增加正比于被吸附熔解Mg的分数，与δ测量的最高²⁶对应于吸附度最高（〜76％）的Mg（-0.08±0.07‰）。吸附的级分中的Mg同位素组成为相应的光，在平均δ ²⁶镁为-0.49‰。在这些实验条件下，次生矿物沉淀和Mg在次生矿物上的吸附对Mg同位素的影响最小。结果表明，细胞表面反应性对Mg同位素分级分离的作用与其他常见的生物过程（如代谢和有机酸产生）不同。通过进一步的研究，镁同位素可用于阐明生物圈在环境中镁循环中的作用。