"Given that genomes are usually well adapted to their environment, knowing LUCA's genome could lend insight into the environmental conditions in which LUCA lived," McInerney said.
For the new study, scientists analyzed the evolutionary relationship of 6.1 million protein-coding genes in 1,847 bacterial and 134 archaeal genomes, aiming to get insight into the biology of LUCA.
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Madeline Weiss, with Heinrich Heine University in Dusseldorf, Germany, and colleagues found that out of 286,514 protein clusters, 355 gene families date back to LUCA, the organism from which both bacteria and archaea emerged.
Extrapolating from that analysis, the scientists infer that LUCA did not need oxygen to grow, that it thrived at relatively high temperatures and that it used carbon dioxide, nitrogen and hydrogen to sustain its metabolic pathways. LUCA was also dependent on metals such as iron, and other elements like selenium, the scientists found.
The presence of a thermophile-specific gene in LUCA buttress the idea that life began at hydrothermal vents, a theory that propels the search for life in ocean-bearing, outer moons of Saturn and Jupiter.
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LUCA's closest relatives alive today are clostridia, a group of anaerobic bacterium that includes pathogens which cause tetanus and botulism, and methanogens, Weiss and colleagues wrote.
"When we look at the inferred metabolism of LUCA, we are looking at the dominant and most successful kind of metabolism on the planet before the Bacteria and Archaea diverged," McInerney said. "This new study provides us with a very intriguing insight into life 4 billion years ago."
Still unknown is whether the 355 gene families identified in the study were in the same cell at the same time, or what other genes were present, he added.