Abstract Free-living and mycorrhizal fungi are able to enhance the weathering of rock and other solid substrates. Deciphering the exact mechanisms of these natural processes requires their experimental simulation. Moreover, by performing these simulations with genetically amenable rock-weathering fungi, one can knock-out certain fungal traits and consequently identify their weathering-relevant function. Here, the effect of the rock-inhabiting fungus, Knufia petricola A95, on the dissolution kinetics of an Fe-bearing olivine (Mg1.86Fe0.19SiO4) is investigated at 25 °C and pH 6 using reproducible batch and mixed flow experiments. The availability of a melanin-deficient mutant (ΔKppks) of K. petricola A95, which produces more extracellular polymeric substances (EPS) than the wild type (WT), enables the comparative study of the role of melanin and EPS in olivine dissolution. In abiotic dissolution experiments, the olivine dissolution rate decreased considerably over time at pH 6 but not at pH 3.5. This inhibition of abiotic olivine dissolution at pH 6 was most likely caused by the in-situ oxidation of ferrous Fe and/or the precipitation of ferric hydroxides at the olivine surface. In corresponding biotic experiments at pH 6, both the wild type K. petricola and its melanin-deficient mutant ΔKppks solubilised and bound significant amounts of Fe released by olivine dissolution. Fe oxidation and precipitation were thus prevented and olivine dissolution proceeded faster than in the abiotic experiments. By sequestering Fe directly at the olivine surface, the attached wild type K. petricola cells were particularly efficient at preventing the oxidation of Fe at the mineral surface: the slowdown of olivine dissolution almost completely disappeared. The attachment capacity of these wild type cells is most likely mediated by wild type-specific EPS. Our presented experimental systems allow the oxidation of mineral-released Fe and include a rock-inhabiting fungus, thus simulating chemical, physical and biological conditions that set dissolution rates in a way that is relevant to natural ecosystems.

中文翻译：

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岩栖真菌 K. petricola A95 如何通过附着增强橄榄石的溶解

摘要 自由生活和菌根真菌能够增强岩石和其他固体基质的风化作用。破译这些自然过程的确切机制需要他们的实验模拟。此外，通过对遗传上适合岩石风化的真菌进行这些模拟，人们可以敲除某些真菌性状，从而确定它们的风化相关功能。在这里，在 25 °C 和 pH 6 条件下，使用可重现的批次和混合流实验研究了岩石栖息真菌 Knufia petricola A95 对含铁橄榄石 (Mg1.86Fe0.19SiO4) 溶解动力学的影响。K. petricola A95 的黑色素缺陷突变体 (ΔKppks) 的可用性，它比野生型 (WT) 产生更多的细胞外聚合物 (EPS)，能够比较研究黑色素和 EPS 在橄榄石溶解中的作用。在非生物溶解实验中，橄榄石的溶解速率在 pH 6 时随时间显着降低，但在 pH 3.5 时则不然。这种在 pH 6 下对非生物橄榄石溶解的抑制很可能是由亚铁的原位氧化和/或氢氧化铁在橄榄石表面的沉淀引起的。在 pH 6 的相应生物实验中，野生型岩蔷薇及其缺乏黑色素的突变体 ΔKppks 溶解并结合了橄榄石溶解释放的大量 Fe。因此，Fe 氧化和沉淀被阻止，橄榄石溶解进行得比非生物实验更快。通过直接在橄榄石表面隔离 Fe，附着的野生型 K. petricola 细胞在防止矿物表面 Fe 氧化方面特别有效：橄榄石溶解的减缓几乎完全消失。这些野生型细胞的附着能力很可能是由野生型特​​异性 EPS 介导的。我们提出的实验系统允许矿物释放的铁氧化，并包括一种栖息在岩石中的真菌，从而模拟化学、物理和生物条件，以与自然生态系统相关的方式设置溶解速率。