Casar Caitlin P, Kruger Brittany R, Osburn Magdalena R
Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL, United States.
Division of Hydrologic Sciences, Desert Research Institute, Las Vegas, NV, United States.
Front Microbiol. 2021 Apr 9;12:658988. doi: 10.3389/fmicb.2021.658988. eCollection 2021.
The continental deep subsurface is likely the largest reservoir of biofilm-based microbial biomass on Earth, but the role of mineral selectivity in regulating its distribution and diversity is unclear. Minerals can produce hotspots for intraterrestrial life by locally enhancing biofilm biomass. Metabolic transformations of minerals by subsurface biofilms may occur widely with the potential to significantly impact subsurface biogeochemical cycles. However, the degree of impact depends upon the amount of biofilm biomass and its relationship to host rock mineralogy, estimates that are currently loosely constrained to non-existent. Here, we use cultivation of biofilms on native rocks and coupled microscopy/spectroscopy to constrain mineral selectivity by biofilms in a deep continental subsurface setting: the Deep Mine Microbial Observatory (DeMMO). Through hotspot analysis and spatial modeling approaches we find that mineral distributions, particularly those putatively metabolized by microbes, indeed drive biofilm distribution at DeMMO, and that bioleaching of pyrite may be a volumetrically important process influencing fluid geochemistry at this site when considered at the kilometer scale. Given the ubiquity of iron-bearing minerals at this site and globally, and the amount of biomass they can support, we posit that rock-hosted biofilms likely contribute significantly to subsurface biogeochemical cycles. As more data becomes available, future efforts to estimate biomass in the continental subsurface should incorporate host rock mineralogy.
大陆深部地下很可能是地球上基于生物膜的微生物生物量的最大储存库，但矿物选择性在调节其分布和多样性方面的作用尚不清楚。矿物可以通过局部增加生物膜生物量为地球内部生命创造热点。地下生物膜对矿物的代谢转化可能广泛发生，有可能显著影响地下生物地球化学循环。然而，影响程度取决于生物膜生物量的数量及其与宿主岩石矿物学的关系，目前这些估计在很大程度上受到限制甚至不存在。在这里，我们利用在天然岩石上培养生物膜以及结合显微镜/光谱学方法，来确定在一个大陆深部地下环境——深部矿井微生物观测站（DeMMO）中生物膜对矿物的选择性。通过热点分析和空间建模方法，我们发现矿物分布，特别是那些可能被微生物代谢的矿物分布，确实驱动了DeMMO处的生物膜分布，并且从千米尺度考虑，黄铁矿的生物浸出可能是一个在体积上对该地点流体地球化学有重要影响的过程。鉴于该地点以及全球范围内含铁矿物的普遍存在，以及它们所能支持的生物量数量，我们认为岩石承载的生物膜可能对地下生物地球化学循环有重大贡献。随着更多数据的获得，未来估计大陆深部地下生物量的工作应纳入宿主岩石矿物学。
