The acid mine drainage ( AMD) environment is considered as a modern analog to environments in the early Earth. The metal-laden, low-pH water of the AMD is similar to certain aqueous environment thought to have existed in Archean and early Proterozoic oceans in areas of active volcanism. Despite the low pH, high metal content, and nutrient-deprived nature of the environment, both prokaryotes and eukaryotes thrive in AMD. Of interest is the acidophilic, photosynthetic microeukaryote Euglena mutabilis. This review provides a comprehensive overview of the biochemistry, physiology, and biogeochemical signatures constructed by Euglenids in AMD and their broad implications in understanding biochemical evolution and paleoenvironmental conditions on the primitive Earth. The formation of biofilms and the conservation of compartmentalized aerobic and anaerobic biosynthetic pathways of wax esters and sterols in mitochondria may have allowed euglenids to survive and diversify on early Earth. The Fe-rich stromatolites, lipids and their carbon isotopic ratios, which are linked to the acidic environment and the unique physiology and biochemistry of the acidophiles are biosignatures that can be used for elucidating the plausible linkage between eukaryotic evolution, oxygenation of the early atmosphere, formation of BIF, and environmental evolution of the early Earth.%现代酸性矿山废水(AMD)环境被认为是地球早期环境的理想对应物.AMD的水环境具有金属含量高、pH低的特点,这与太古代-早元古代时期海洋的某些环境条件十分类似.然而,尽管AMD的环境条件恶劣,但仍然栖息着非常丰富的原核和真核微生物,在这其中那些嗜酸的、营光合作用的真核微生物类群(特别是Euglena mutabilis)更是引起众多科学家极大的研究兴趣.本文全面概述了在AMD环境中发现的真核微生物Euglenids种群的生物化学、生理学和生物地球化学特征,以及这些特征对于理解生命演化和早期地球环境条件等方面的指示性作用.Euglenids的细胞具备区域化功能,因而具备需氧和厌氧的蜡酯和甾醇的双生物合成途径,同时它们还可以形成生物膜,所有这些均使得Euglenids能够在早期地球极端恶劣的环境条件下生存并持续演化.在AMD酸性环境中发育的富铁叠层石、嗜酸微生物的脂类化合物及其碳同位素比值以及它们独特的生理和生化特征可用于阐述真核生物的演化、地球早期大气中氧气的产生、条带状富铁建造的形成以及地球早期的环境演化等.
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