Dubey Anant Aishwarya, Toprak Pelina, Pring Allan, Rodriguez-Navarro Carlos, Mukherjee Abhijit, Dhami Navdeep K
School of Civil and Mechanical Engineering, Curtin University, Perth, Australia.
School of Physics, Chemistry and Earth Sciences, University of Adelaide, Adelaide, Australia.
Sci Rep. 2025 Aug 11;15(1):29368. doi: 10.1038/s41598-025-14083-z.
Bacterial mineralisation of calcium carbonates (CaCO) has become a focal point of interest in the scientific community owing to their versatile applications as biomaterials. However, despite extensive research, the knowledge on factors influencing biogenic CaCO polymorph (calcite, vaterite or aragonite) selection in nature remains obscure. Bacterial mineralisation happens in nature on diverse substrates by different pathways, often in the presence of organic matter such as biofilm and extracellular polymeric substances (EPS) secreted with the regular metabolic activities of microbes. This study examines the bacterial CaCO mineralisation process by two distinct pathways on different natural substrates with advanced analytical techniques, including Time of Flight- Secondary Ions Mass Spectrometry (ToF-SIMS). A high EPS-producing microbe (Bacillus subtilis, BS) was compared with the standard ureolytic strain (Sporosarcina pasteurii, SP). Natural geological minerals, including apatite, calcite and quartz, were selected as substrates. This study demonstrates that SP favours the precipitation of rhombohedral calcite crystals (2 to 40 μm in size), regardless of the mineral substrate. In contrast, the EPS-producing BS culture induced the formation of significantly larger vaterite structures (20 to 100 μm in size) in spheroid and hexagonal shapes. The mineralogy of precipitates was confirmed with Raman spectroscopy. ToF-SIMS enabled the spatial tracking of organic macromolecules and the adsorption of calcium ions on them. The functional groups of the EPS involved in these interactions were characterised by Fourier Transform Infrared Spectroscopy (FTIR). This study reveals that microbial activity dominates over substrate mineralogy in selecting the phase and shaping the morphology of biogenic CaCO, with EPS playing a crucial role in promoting the aggregation of small nanocrystals into large vaterite structures and their stabilisation.
由于碳酸钙（CaCO₃）作为生物材料具有多种用途，其细菌矿化已成为科学界关注的焦点。然而，尽管进行了广泛研究，但关于影响自然界中生物成因碳酸钙多晶型（方解石、球霰石或文石）选择的因素的认识仍然模糊不清。细菌矿化在自然界中通过不同途径在多种底物上发生，通常是在存在诸如生物膜和微生物正常代谢活动分泌的胞外聚合物（EPS）等有机物的情况下。本研究采用先进的分析技术，包括飞行时间二次离子质谱（ToF-SIMS），通过两种不同途径在不同天然底物上研究细菌碳酸钙矿化过程。将一种高产EPS的微生物（枯草芽孢杆菌，BS）与标准尿素分解菌株（巴氏芽孢八叠球菌，SP）进行比较。选择包括磷灰石、方解石和石英在内的天然地质矿物作为底物。本研究表明，无论矿物底物如何，SP都有利于菱面体方解石晶体（尺寸为2至40μm）的沉淀。相比之下，产生EPS的BS培养物诱导形成了尺寸明显更大的球状和六边形球霰石结构（尺寸为20至100μm）。用拉曼光谱确认了沉淀物的矿物学。ToF-SIMS能够对有机大分子进行空间追踪以及钙离子在其上的吸附情况。通过傅里叶变换红外光谱（FTIR）对参与这些相互作用的EPS的官能团进行了表征。本研究表明，在选择生物成因碳酸钙的晶相和塑造其形态方面，微生物活性比底物矿物学更为重要，EPS在促进小纳米晶体聚集成大的球霰石结构及其稳定化过程中起着关键作用。
