Early Life Traces & Evolution-Astrobiology, UR Astrobiology, University of Liège, Liège, Belgium.
Commission for the Geological Map of the World, Paris, France.
Nat Commun. 2022 Jan 10;13(1):146. doi: 10.1038/s41467-021-27810-7.
The acquisition of photosynthesis is a fundamental step in the evolution of eukaryotes. However, few phototrophic organisms are unambiguously recognized in the Precambrian record. The in situ detection of metabolic byproducts in individual microfossils is the key for the direct identification of their metabolisms. Here, we report a new integrative methodology using synchrotron-based X-ray fluorescence and absorption. We evidence bound nickel-geoporphyrins moieties in low-grade metamorphic rocks, preserved in situ within cells of a ~1 Gyr-old multicellular eukaryote, Arctacellularia tetragonala. We identify these moieties as chlorophyll derivatives, indicating that A. tetragonala was a phototrophic eukaryote, one of the first unambiguous algae. This new approach, applicable to overmature rocks, creates a strong new proxy to understand the evolution of phototrophy and diversification of early ecosystems.
光合作用的获得是真核生物进化的一个基本步骤。然而，在前寒武纪记录中，很少有明确的光养生物被识别。在单个微生物化石中直接检测代谢副产物是直接鉴定其代谢途径的关键。在这里，我们报告了一种新的综合方法，使用同步加速器基于 X 射线荧光和吸收。我们在约 10 亿年前的多细胞真核生物 Arctacellularia tetragonala 的细胞内原位保存的低变质岩石中发现了结合的镍-地质卟啉部分。我们将这些部分鉴定为叶绿素衍生物，表明 A. tetragonala 是一种光合真核生物，是最早的明确藻类之一。这种新方法适用于过度成熟的岩石，为理解光合作用的进化和早期生态系统的多样化创造了一个强有力的新指标。
