Sánchez-Román Mónica, Chandra Viswasanthi, Mulder Sebastian, Areias Camila, Reijmer John, Vahrenkamp Volker
Geobiology Laboratory, Earth Sciences Department, Faculty of Science, Vrije Universiteit, Amsterdam, The Netherlands.
Ali I. Al-Naimi Petroleum Engineering Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Sci Rep. 2025 Jan 2;15(1):561. doi: 10.1038/s41598-024-84407-y.
Microbial impacts on early carbonate diagenesis, particularly the formation of Mg-carbonates at low temperatures, have long eluded scientists. Our breakthrough laboratory experiments with two species of halophilic aerobic bacteria and marine carbonate grains reveal that these bacteria created a distinctive protodolomite (disordered dolomite) rim around the grains. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) confirmed the protodolomite formation, while solid-state nuclear magnetic resonance (NMR) revealed bacterial interactions with carboxylated organic matter, such as extracellular polymeric substances (EPS). We observed a significant carbon isotope fractionation (average δC = 11.3‰) and notable changes in Mg/Ca ratios throughout the experiments. Initial medium δC was - 18‰, sterile sediments were at 2‰ (n = 12), bacterial-altered sediments were - 6.8‰ (n = 12), and final medium δC was - 4.7‰. These results highlight the role of bacteria in driving organic carbon sequestration into Mg-rich carbonates and demonstrate the utility of NMR as a tool for detecting microbial biosignatures. This has significant implications for understanding carbonate diagenesis (dissolution and reprecipitation), climate science, and extraterrestrial research.
微生物对早期碳酸盐成岩作用的影响，尤其是低温下镁碳酸盐的形成，长期以来一直困扰着科学家。我们用两种嗜盐需氧细菌和海洋碳酸盐颗粒进行的突破性实验室实验表明，这些细菌在颗粒周围形成了独特的原生白云石（无序白云石）边缘。扫描电子显微镜（SEM）和X射线衍射（XRD）证实了原生白云石的形成，而固态核磁共振（NMR）揭示了细菌与羧化有机物（如胞外聚合物（EPS））的相互作用。在整个实验过程中，我们观察到显著的碳同位素分馏（平均δC = 11.3‰）和Mg/Ca比值的显著变化。初始培养基δC为-18‰，无菌沉积物为2‰（n = 12），细菌改变的沉积物为-6.8‰（n = 12），最终培养基δC为-4.7‰。这些结果突出了细菌在推动有机碳固存到富含镁的碳酸盐中的作用，并证明了核磁共振作为检测微生物生物标志的工具的实用性。这对理解碳酸盐成岩作用（溶解和再沉淀）、气候科学和外星研究具有重要意义。
