Potential energy sources for the deep continental biosphere in isolated anoxic brines
Potential energy sources for the deep continental biosphere in isolated anoxic brines
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DOI：
10.1016/j.epsl.2022.117720
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发表时间：
2022-10
影响因子：
5.3
通讯作者：
William S. Dowd;C. Schuler;C. Santelli;B. Toner;C. Sheik;K. Pehr;J. Mcdermott
中科院分区：
文献类型：
--
作者：
William S. Dowd;C. Schuler;C. Santelli;B. Toner;C. Sheik;K. Pehr;J. Mcdermott
在前寒武纪地盾的孤立裂缝网络中，长期的水和岩石相互作用产生了含盐缺氧流体，这些流体在大陆地下深处承载着现存的微生物群落。在这些环境中没有光和氧气（O2）。因此，栖息在这些系统中的化能营养生物依靠厌氧反应获得能量。可行的电子供体包括短链烷烃，如甲烷（CH 4）和C2+烷烃，而替代的电子受体包括硫酸盐（SO 2− 4），硝酸盐（NO− 3）和三价铁（Fe 3+）。在这里，我们限制了新太古代基岩中微生物的潜在能源，位于美国明尼苏达州Soudan地下矿山州立公园（地表以下713.5米）的第27层西漂移。模拟了11个反应的吉布斯自由能（ΔG），并表示为单位质量流体的有效化学势能（J/kg流体）。在本研究中，涉及CH 4被SO2 − 4氧化的代谢反应将产生最高的反应势能（− 111 J/kg流体）。二甲胺分解产甲烷的自由能（DMA;∑（CH 3）2NH（aq））是放能的，但单位质量流体的有效能量接近于零，这表明在苏丹，DMA可以快速循环产生生物CH 4.我们研究了所有可能的途径，其中CH 4和其他短链烷烃可能形成。常规的δ 13 C CH 4值和C1/C2+丰度比支持CH 4的生物和非生物混合起源。双取代的“成团”CH 4同位素13 CH 3D值与84-89° C的地层温度一致，超过了目前11.5-12.1° C的环境条件这些估计的形成温度太低，甲烷4形成单独通过有机物的热降解。此外，低或检测不到的H2排除了积极的非自然发生的CH 4从CO2还原。更有可能的是，大量CH 4池反映了Δ 13 CH 3D值在11.5-12.1° C平衡的微生物CH 4和在> 100° C温度下形成的产热CH 4的混合物了解这些电子供体的起源和循环有助于从根本上了解微生物活动如何在长时间尺度上促进，维持或抑制这些孤立系统的可居住性。
In isolated fracture networks in the Precambrian Shield, long-term water and rock interactions produce saline anoxic fluids that host extant microbial communities deep within the continental subsurface. Light and oxygen (O 2) are absent in these environments. Thus, chemotrophic organisms inhabiting these systems rely on anaerobic reactions for energy. Viable electron donors include short-chain alkanes, such as methane (CH 4) and C 2+ alkanes, while alternative electron acceptors include sulfate (SO 2− 4), nitrate (NO− 3), and ferric iron (Fe 3+). Here, we constrain the potential sources of energy for microorganisms in Neoarchean bedrock on the 27th level west drift of the Soudan Underground Mine State Park, MN, USA (713.5 meters below the surface). The Gibbs Free Energy (ΔG) of 11 reactions are modeled and expressed as available chemical potential energy per mass fluid (J/kg fluid). Metabolic reactions involving CH 4 oxidation by SO 2− 4 would yield the highest potential energy of reactions modeled in this study (− 111 J/kg fluid). The free energy for methanogenesis via the breakdown of dimethylamine (DMA;∑(CH 3) 2 NH (aq)) is exergonic but with near-zero available energy per mass fluid, suggesting that DMA may be cycled quickly to produce biological CH 4 at Soudan. We examine all the possible pathways by which CH 4 and other short-chain alkanes may be formed. Conventional δ 13 C CH4 values and C 1/C 2+ abundance ratios support a mixed biological and non-biological origin of CH 4. Doubly substituted ‘clumped’CH 4 isotope 13 CH 3 D values are consistent with formation temperatures of 84-89° C that exceed current environmental conditions of 11.5-12.1° C. These estimated formation temperatures are too low for CH 4 to be formed solely through thermogenic degradation of organic matter. Further, low or undetectable H 2 rules out active abiogenesis of CH 4 from CO 2 reduction. It is more likely that the bulk CH 4 pool reflects a mixture of microbial CH 4 with Δ 13 CH 3 D values equilibrated at 11.5-12.1° C and thermogenic CH 4 formed at temperatures> 100° C. Understanding the origin and cycling of these electron donors contributes to a fundamental understanding of how microbial activity may promote, maintain, or suppress the habitability of these isolated systems over long timescales.