Despite years of progress, the origin of life remains one of science’s most enduring mysteries.
“The most important feature of biology, living things are made up of cells, through which you pass genetic information DNA“They use protein enzymes to power their metabolism, and all of that emerged through specific processes in a very early evolutionary history,” says Aaron Goldman, assistant professor of biology at Oberlin College. “Understanding how these basic biological systems first formed will not only give us insight into how life works at a fundamental level, but what life actually is in the first place and how we can search for it beyond Earth.”
The question of how life first emerged is usually studied through laboratory experiments that simulate the environments of early Earth and look for chemistry that could create the same kinds of biomolecules and metabolic reactions we see in living things today. This is known as a “bottom-up” approach because it works with materials that would otherwise be on Earth for prebiotics.
While these so-called “prebiotic chemistry” experiments have successfully demonstrated how to live may have Growing up, they can’t tell us what life is actually like an act arise. Meanwhile, other research is using techniques from evolutionary biology to reconstruct what early life forms might have looked like based on data from life today. This is known as the “top-down” approach and can tell us about the history of life on Earth.
However, top-down research can only look back as there were genes still preserved in organisms today, and thus not all the way to the origin of life. Despite their limitations, top-down and bottom-up research aim at the common goal of discovering the origins of life, and ideally, their answers should converge on a common set of conditions.
A new article published by Goldman, Lori Barge (Research Scientist in Astrobiology at the NASAjet propulsion plant (Jet Propulsion Laboratory)) and colleagues, to fill this methodological gap. The authors argue that combining bottom-up laboratory research on plausible paths toward the origin of life with top-down evolutionary reconstructions of early life forms can be used to discover how life really originated on the early Earth.
In their paper, the authors describe a phenomenon fundamental to life today that can be studied by combining both bottom-up and top-down research: electron transport chains.
Electron transport chains are a type of metabolic system used by organisms across the tree of life, from bacteria to humans, to produce usable forms of chemical energy. The many different types of electron transport chains are specific to each form of life and the energy metabolism they use: for example, our mitochondria contain an electron transport chain associated with heterotrophic (food-consuming) energy metabolism; Whereas, plants have a completely different electron transport chain attached to them Photosynthesis (Generate energy from sunlight).
And throughout the microbial world, organisms use a wide range of electron transport chains associated with a variety of different energy metabolic processes. But, despite these differences, the authors describe evidence from top-down research that this type of metabolic strategy was used by very early forms of life and provide several models for ancestral electron transport chains that can be traced back to very early evolutionary history.
They also surveyed current, bottom-up evidence that even before life as we know it emerged, electron transport chain-like chemistry could have been facilitated by minerals and waters of the early Earth’s oceans. Inspired by these observations, the authors outline future research strategies that combine top-down and bottom-up research on the earliest history of electron transport chains in order to gain a better understanding of ancient energy metabolism and the origin of life more broadly.
This study is the culmination of five years of previous work by this multidisciplinary, interdisciplinary team led by Barge at JPL, which was funded by the NASA-NSF Ideas Lab for the Origins of Life to study how metabolic interactions arose in geological environments on early Earth. . The team’s previous work has looked, for example, at specific electron transport chain interactions driven by metals (led by Jessica Weber, a research scientist at JPL); how ancient enzymes may have Prebiotic chemistries are included in their active sites (led by Goldman); And Microbial metabolism in highly energy-limited environments (Led by Doug LaRue, of the University of Southern California).
“The emergence of metabolism is a multidisciplinary question and so we need a multidisciplinary team to study this,” Barge says. “Our work has used techniques from chemistry, geology, biology, and computational modeling, to combine these top-down and bottom-up approaches, and this type of collaboration will be important for future studies of prebiotic metabolic pathways.”
Reference: “Electron Transport Chains as a Window to the Early Stages of Evolution” by Aaron D. Proceedings of the National Academy of Sciences.
The study was funded by the National Aeronautics and Space Administration.
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