University of Düsseldorf Study Finds Two Independent Origins of Life
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An international research team led by biologists at the University of Düsseldorf has found evidence that free-living cells emerged twice independently as bacteria and archaea diverged over 4 billion years ago. Their analysis, published in Science Advances, reveals that the last universal common ancestor (LUCA) possessed enzymes for only about half of the 420 metabolic reactions essential for life, with the rest catalyzed by metals in ancient hydrothermal vents.
The Enzyme Divide Between Bacteria and Archaea
The team compared genomes, protein structures and chemical reactions across bacteria and archaea, tracing the origin of enzymes. They found that LUCA — the last universal common ancestor — already had enzymes for about half of the 420 universally conserved metabolic reactions. The enzymes for the remaining half arose later and independently in the two lineages, indicating that free-living bacterial and archaeal cells evolved separately, according to the study in Science Advances. This divergence means that key metabolic pathways were completed only after bacteria and archaea split from LUCA and emerged from hydrothermal vents.
Metals as Proto-Enzymes in Early Life
The missing enzymes were likely replaced by metals such as iron, nickel and molybdenum present in hydrothermal vent environments, the researchers say. Co-author and inorganic chemist Harun Tüysüz notes that metals naturally occurring in these vents can substitute for a surprisingly large number of enzymes. Lead author Natalia Mrnjavac adds that pioneer bacteria and archaea made their first attempts at life outside the vents, using these metal catalysts. The findings imply that life's earliest metabolism was half-enzymatic and half-geochemical, with the transition to full enzymatic control occurring after the two lineages separated.
What's Next
The research group now plans to test experimentally which specific metals could have catalyzed the ancestral reactions. The findings may also guide the search for life on other planets, though it remains unclear how the first cells eventually replaced metal catalysts with enzymes entirely.
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University of Düsseldorf Study Finds Two Independent Origins of Life
