Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA; NASA Center for Early Life and Evolution, University of Wisconsin-Madison, Madison, WI 53706, USA.
School of Oceanography, University of Washington, Seattle, WA 98195, USA.
Cell Rep. 2022 Apr 26;39(4):110726. doi: 10.1016/j.celrep.2022.110726.
The earliest geochemical indicators of microbes-and the enzymes that powered them-extend back ∼3.8 Ga on Earth. Paleobiologists often attempt to understand these indicators by assuming that the behaviors of extant microbes and enzymes are uniform with those of their predecessors. This consistency in behavior seems at odds with our understanding of the inherent variability of living systems. Here, we examine whether a uniformitarian assumption for an enzyme thought to generate carbon isotope indicators of biological activity, RuBisCO, can be corroborated by independently studying the history of changes recorded within RuBisCO's genetic sequences. We resurrected a Precambrian-age RuBisCO by engineering its ancient DNA inside a cyanobacterium genome and measured the engineered organism's fitness and carbon-isotope-discrimination profile. Results indicate that Precambrian uniformitarian assumptions may be warranted but with important caveats. Experimental studies illuminating early innovations are crucial to explore the molecular foundations of life's earliest traces.
最早的微生物地球化学指标——以及为其提供动力的酶——可以追溯到地球 38 亿年前。古生物学家通常试图通过假设现存微生物和酶的行为与它们的祖先一致来理解这些指标。这种行为的一致性似乎与我们对生命系统固有可变性的理解相矛盾。在这里，我们通过独立研究记录在 RuBisCO 遗传序列中的变化历史，来检验一种认为能够产生生物活性碳同位素指标的酶 RuBisCO 的均变论假设是否可以得到证实。我们通过在蓝藻基因组中设计其古老 DNA 来复活一种前寒武纪时代的 RuBisCO，并测量了工程生物体的适应性和碳同位素分辨特征。结果表明，前寒武纪的均变论假设可能是合理的，但有重要的警告。阐明早期创新的实验研究对于探索生命最早痕迹的分子基础至关重要。
