Many have postulated that a specific microbial metabolism or the presence of microbes or/and their extracellular polymeric substances (EPS) can lead to the formation of dolomite. Although now there is the consensus that dolomite can be formed in the presence of microorganisms, the exact nature of the involvement of microbes in the dolomite nucleation remains a matter of debate. The focus is now in understanding how microbial mats determine the mineralogy of dolomite. Here we report the effect of the EPS extracted from phototrophic microbial mat isolated from a sabkha in Qatar dominated by cyanobacteria (Lyngbya aestuarii) in the formation of dolomite precursors at 25 °C and 40 °C. Both the temperature and the presence of EPS impact the size and morphology of minerals, promoting spherulitic and dumbbell growth in sulfate free solutions. The formation of proto-dolomite was enhanced by the abundance of carboxylated molecules in EPS which controlled the polymorphism of carbonates. Our study emphasizes the dual importance of organic matter and temperature in dolomite formation and their impact on mineral morphology and chemical composition in sabkhas.

中文翻译：

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光养微生物垫胞外聚合物对原白云石的有机矿化：晶体尺寸的控制及其对碳酸盐沉积系统的影响

许多人假设特定的微生物代谢或微生物或/及其细胞外聚合物 (EPS) 的存在会导致白云石的形成。尽管现在人们一致认为白云岩可以在微生物存在下形成，但微生物参与白云岩成核的确切性质仍然存在争议。现在的重点是了解微生物垫如何确定白云石的矿物学。在这里，我们报告了从以蓝藻（Lyngbya aestuarii）为主的卡塔尔 sabkha 中分离的光养微生物垫中提取的 EPS 在 25°C 和 40°C 下形成白云石前体的影响。温度和 EPS 的存在都会影响矿物质的大小和形态，促进无硫酸盐溶液中的球状和哑铃状生长。EPS中丰富的羧化分子控制了碳酸盐的多态性，从而促进了原白云石的形成。我们的研究强调了有机质和温度在白云岩形成中的双重重要性及其对矿区矿物形态和化学成分的影响。