nucleation

LIT-1561: Gene ancestries reveal diverse microbial associations during eukaryogenesis

2 min read

Properties5
StatusActive — read in full 2026-10-27 (NOTE-1237) from the PubMed Central copy of the version of record (PMC13468126, open access); worth reading as the strongest current case that the last eukaryotic common ancestor received genes from bacterial donors besides the mitochondrial ancestor, Myxococcota and Planctomycetota, in shares comparable to the accepted partners', and for its ordering of those acquisitions as waves (THEORY-1105). Read it knowing that its thresholds are calibrated on the accepted partners; that its key controls are in a supplement; that the ordering rests on stem lengths as a clock, which Tobiasson et al. dispute; and that the authors say their data cannot tell whether any donor was a symbiont.
Version3
Tagsendosymbiosis, natural-sciences
Cited as “paper” byNOTE-1237 — Bernabeu, Manzano-Morales, Marcet-Houben & Gabaldón — Gene ancestries reveal diverse microbial associations during eukaryogenesis
Cited as “source” byTHEORY-1105 — In Bernabeu, Manzano-Morales, Marcet-Houben and Gabaldón's reconstruction of the last eukaryotic common ancestor's proteome, two bacterial phyla besides the mitochondrial ancestor, Myxococcota and Planctomycetota, each account for a share of the proteome comparable to that of Alphaproteobacteria and Asgard archaea under thresholds calibrated on those accepted partners, and stem-length distributions order the acquisitions as waves, Asgard first, then Planctomycetota, then the mitochondrial ancestor and Myxococcota together; the authors read this as serial associations with several partners, while conceding that their data cannot say whether any donor was a symbiont, THEORY-1215 — Besides Asgard archaea and the alphaproteobacterial ancestor of mitochondria, Myxococcota and Planctomycetota were major donors of genes to the eukaryotic lineage before its last common ancestor, in waves: Asgard first, then Planctomycetota before the mitochondrion, then the mitochondrial ancestor and Myxococcota together

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Bernabeu, M., Manzano-Morales, S., Marcet-Houben, M. & Gabaldón, T. (2026). Gene ancestries reveal diverse microbial associations during eukaryogenesis. Nature 656(8127): 399–405. doi:10.1038/s41586-026-10639-9.

Key takeaways

From the reading, NOTE-1237.

  • Two more donors. Under thresholds chosen to maximize assignments to Alphaproteobacteria and Asgard, Myxococcota and Planctomycetota hold comparable shares in every dataset (THEORY-1105).
  • Not misplaced mitochondrial genes. With Alphaproteobacteria removed from the database, their genes fall to Gammaproteobacteria first; the new donors do not fit that pattern.
  • Waves, by stem length. Asgard first, then Planctomycetota, then the mitochondrial ancestor and Myxococcota. The ordering depends on stem lengths as relative times, which Tobiasson et al. dispute.
  • Viruses as carriers. About 4.5% of families have a viral sister, 74% of them giant viruses, some with prokaryotic genes behind them.
  • Donors, not shown partners. “our data do not provide information on the host or endosymbiotic nature of any partner.”

Why this is here

A2 cites it as the distributed side of the live disagreement, and rates it “High”. A2’s own caution, kept here: a history of horizontal gene transfer does not by itself show a past endosymbiosis.

The reading confirms the caution: the authors make it themselves. Like LIT-1558, the paper places the mitochondrion late, and both have bacterial genes arriving before it. The disagreement between them is over how those genes are grouped and timed (NOTE-1237).

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