Limited taxonomic classification is possible for Archaean microbial mats and this is a fundamental limitation in constraining early ecosystems. Applying Fourier transform infrared spectroscopy (FTIR), a powerful tool for identifying vibrational motions attributable to specific functional groups, we characterized fossilized biopolymers in 3.5–3.3 Ga microbial mats from the Barberton greenstone belt (South Africa). Microbial mats from four Palaeoarchaean horizons exhibit significant differences in taxonomically informative aliphatic contents, despite high aromaticity. This reflects precursor biological heterogeneity since all horizons show equally exceptional preservation and underwent similar grades of metamorphism. Low methylene to end‐methyl (CH₂/CH₃) absorbance ratios in mats from the 3.472 Ga Middle Marker horizon signify short, highly branched n‐alkanes interpreted as isoprenoid chains forming archaeal membranes. Mats from the 3.45 Ga Hooggenoeg Chert H5c, 3.334 Ga Footbridge Chert, and 3.33 Ga Josefsdal Chert exhibit higher CH₂/CH₃ ratios suggesting mostly longer, unbranched fatty acids from bacterial lipid precursors. Absorbance ratios of end‐methyl to methylene (CH₃/CH₂) in Hooggenoeg, Josefsdal and Footbridge mats yield a range of values (0.20–0.80) suggesting mixed bacterial and archaeal architect communities based on comparison with modern examples. Higher (0.78–1.25) CH₃/CH₂ ratios in the Middle Marker mats identify Archaea. This exceptional preservation reflects early, rapid silicification preventing the alteration of biogeochemical signals inherited from biomass. Since silicification commenced during the lifetime of the microbial mat, FTIR signals estimate the affinities of the architect community and may be used in the reconstruction of Archaean ecosystems. Together, these results show that Bacteria and Archaea flourished together in Earth's earliest ecosystems.

中文翻译：

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细菌和古细菌的多样化群落在古古细菌（3.5-3.3 Ga）微生物垫中蓬勃发展

对于古生菌垫来说，有限的分类学分类是可能的，这是限制早期生态系统的基本限制。应用傅立叶变换红外光谱法（FTIR），一种用于识别归因于特定官能团的振动运动的有力工具，我们对来自Barberton绿岩带（南非）的3.5–3.3 Ga微生物垫中的化石生物聚合物进行了表征。尽管芳香性很高，但来自四个古生界的微生物垫在分类学信息丰富的脂肪含量上却表现出显着差异。这反映了前体的生物异质性，因为所有视野都表现出同样出色的保存能力，并且经历了相似等级的变质作用。低亚甲基至末端甲基（CH ₂ / CH ₃）从3.472 Ga中间标记水平开始的垫中的吸光度比表示短而高度分支的正构烷烃，被解释为形成古细菌膜的类异戊二烯链。来自3.45 Ga Hooggenoeg Chert H5c，3.334 Ga行人天桥Chert和3.33 Ga Josefsdal Chert的垫子具有较高的CH ₂ / CH ₃比，表明来自细菌脂质前体的更长的直链脂肪酸。Hooggenoeg，Josefsdal和Footbridge席子中的末端甲基与亚甲基（CH ₃ / CH ₂）的吸光度比值范围为（0.20–0.80），这表明与现代实例相比，细菌和古细菌建筑群混杂。更高（0.78–1.25）CH ₃ / CH ₂中标记垫上的比率表示古细菌。这种特殊的保存反映了早期，快速的硅化作用，防止了从生物质继承的生物地球化学信号的改变。由于硅化作用是在微生物垫的生命周期内开始的，因此FTIR信号估计了建筑师社区的亲和力，可用于重建古生生态系统。这些结果共同表明，细菌和古细菌在地球最早的生态系统中共同繁荣。