LUCA latest: most current study (Introduction)

by David Turell , Monday, July 15, 2024, 21:29 (129 days ago) @ David Turell

Puts LUCA at 4.2 billion years ago:

https://www.science.org/content/article/our-last-common-ancestor-lived-4-2-billion-year...

"The last ancestor shared by all living organisms was a microbe that lived 4.2 billion years ago, had a fairly large genome encoding some 2600 proteins, enjoyed a diet of hydrogen gas and carbon dioxide, and harbored a rudimentary immune system for fighting off viral invaders. That’s the conclusion of a new study that compared the genomes of a diverse range of 700 modern microbes and looked for commonalities to identify which features arose first. Although the analysis doesn’t reveal how life got its start, it suggests a complex cellular organism somewhat similar to modern microbes evolved only a few hundred million years after Earth’s formation.

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"Moody and his colleagues have gone a step further. They focused on five sets of “paralog,” or duplicated, genes that were found in multiple bacteria and archaea, suggesting the doubling happened prior to LUCA’s split into those descendants. Tracking whether a mutation is in both copies of those genes or just one makes it easier to pin down the timing of their duplication and thus the ages of common ancestors, Moody says.

"In so doing, their analysis suggested LUCA lived some 4.2 billion years ago. “It’s maybe a little bit earlier than other estimates, but not much,” says Rika Anderson, an evolutionary microbiologist at Carleton College who was not involved with the work.

"To probe LUCA’s lifestyle like Martin did, Moody’s group tracked 57 “marker” genes across 350 bacteria and 350 archaea species to construct a tree of life. That’s an advance over Martin’s team, which tracked genes shared by at least two orders of bacteria and two orders of archaea, Moody says. His team then separately tracked the evolutionary patterns of individual genes and gene families of all the available genes in those bacteria and archaea cataloged in a commonly used genomic database. By comparing the evolutionary histories of individual genes with those of the species, they could better determine what genes were duplicated, lost, or underwent horizontal gene transfer. From that, they deduced what was present in LUCA.

“'It’s a more robust approach,” Anderson says. But Martin counters that despite this effort “they get exactly the same result, 8 years later.”

"Indeed, the U.K. team’s analysis suggested LUCA fueled itself on a diet of carbon dioxide (CO2) and H2, as Martin has found. But they also found evidence LUCA had a gene that could have protected it from ultraviolet light, which suggests the microbe might have lived in surface waters, where it could have captured CO2 and H2 from the atmosphere, rather than at deep-sea vents. Still, like Martin, they spotted the signature of an enzyme called reverse gyrase that is commonly found in thermophiles, which they acknowledge means LUCA could also have thrived around those vents.

"Moody also found something new: that LUCA likely had 19 CRISPR-Cas9 genes, an apparatus modern bacteria rely on to chop up the genetic material of viral invaders (and the inspiration for the versatile genome editor now used in many fields). “LUCA had this early immune system as a way of avoiding viruses,” Moody says.

"That thrills Kaçar, as it hints at a thriving ecosystem of microbes and pathogens that far back. Anderson is equally enthused, noting that CRISPR-Cas9 systems are “kind of sophisticated.” That means in only a few hundred million years, early life managed to evolve complex microbes whose interactions quickly settled into the scaffolding of a simple ecosystem—a feat that modern studies trying to depict the long-lost LUCA can’t yet explain."

Comment: only 300.000 years after Earth formation, and complex life appeared. Much too quick for random mutations doing the job. More evidence for design.