Researchers Trace 12,907 LECA Protein Families to Multiple Bacterial Donors and 4.5% Virus-Mediated Transfers
Updated
Updated · Nature.com · Jun 10
Researchers Trace 12,907 LECA Protein Families to Multiple Bacterial Donors and 4.5% Virus-Mediated Transfers
2 articles · Updated · Nature.com · Jun 10
Summary
A revised reconstruction of the last eukaryotic common ancestor found multiple waves of horizontal gene transfer from bacteria, with some acquisitions likely predating mitochondrial endosymbiosis.
Across an average 12,907 protein families in the relaxed LECA set, the strongest noncanonical donor signals came from Myxococcota at 3.92% and Planctomycetota at 2.24%, alongside Alphaproteobacteria and Asgard archaea.
About 4.5% of LECA phylogenies showed viral sister groups, and 74% of those pointed to Nucleocytoviricota, suggesting giant-virus relatives helped shuttle prokaryotic genes into early eukaryotes.
The reconstructed LECA remained a complex, likely aerobic heterotroph with mitochondria, endocytosis and intracellular transport, while 33% of gene families appeared to be eukaryotic innovations.
The study argues eukaryotes arose through serial interactions in dense microbial ecosystems rather than a single binary symbiosis, challenging one-off origin models.
Could ancient viruses have been the architects that helped build our complex cells?
Our cells are a mosaic of bacteria and viruses. Where does the 'us' begin?
Did a microbial village, not a single merger, create the first complex life?
The Viral Origins of Eukaryotic Complexity: 12,907 Protein Families in LECA’s Genetic Blueprint
Overview
In April 2026, a groundbreaking study delivered the most comprehensive reconstruction of the Last Eukaryotic Common Ancestor (LECA) proteome, identifying 12,907 protein families at its core. This research offered unprecedented insights into the genetic makeup and evolutionary history of early eukaryotes, revealing that LECA's proteome was a complex mosaic shaped by substantial contributions from various bacterial lineages. Notably, bacterial donors such as Alphaproteobacteria, Myxococcota, and Planctomycetota played significant roles, highlighting the intricate and diverse origins of eukaryotic genomes and underscoring the complexity of eukaryotic evolution.