nucleation

THEORY-1205: Eukaryotes began in a syntrophic partnership: an archaeal host fermented sugars and passed reducing equivalents to an alphaproteobacterial endosymbiont that contributed a TCA cycle and an electron transport chain, which is why the last eukaryotic common ancestor's central carbon metabolism is archaeal in cytosolic glycolysis and the pentose phosphate pathway and alphaproteobacterial in the mitochondrial TCA cycle

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Properties5
StatusProposed
Tagsendosymbiosis, natural-sciences
SourceLIT-1564 — Chimeric origins and dynamic evolution of central carbon metabolism in eukaryotes
ExtendsTHEORY-1109 — Santana-Molina, Williams, Snel and Spang find that the last eukaryotic common ancestor's central carbon metabolism was chimeric: a few Asgard-archaeal enzymes in cytosolic glycolysis and the pentose phosphate pathway, four placed with Asgard archaea at bootstrap 39–97% and two ambiguously, most alphaproteobacterial ones in the mitochondrial TCA cycle and pyruvate conversion, and others from various bacteria with no third dominant donor, since remodelled by loss, horizontal replacement and retargeting so that compartment no longer follows origin; the authors take the cytosol–mitochondrion split as support for syntrophy
Bears onQUESTION-277 — When formerly autonomous partners come to depend on one another, which of mutual dependence, reproductive cohesion, the distribution of essential functions across genomes, the host's regulatory control and the alignment of selection does each route to dependence bring about, and which of them, alone or together, make the partnership a new evolutionary individual?

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Source

Santana-Molina, Williams, Snel & Spang (2025), LIT-1564, read in full in NOTE-1239. The authors: “our results support the view of syntrophic interactions between host and endosymbiont”.

Where the evidence stands

What the paper shows, and what it does not, is THEORY-1109, Active, which this entry extends: that entry is the reading, this one the thesis. The promote_when above is THEORY-1109’s condition before the twenty-second status review promoted it, carried here unchanged, because it asks what would make the thesis true and not what the paper says.

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