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Evidence for an early prokaryotic endosymbiosis


Endosymbioses have dramatically altered eukaryotic life, but are thought to have negligibly affected prokaryotic evolution. Here, by analysing the flows of protein families, I present evidence that the double-membrane, Gram-negative prokaryotes were formed as the result of a symbiosis between an ancient actinobacterium and an ancient clostridium. The resulting taxon has been extraordinarily successful, and has profoundly altered the evolution of life by providing endosymbionts necessary for the emergence of eukaryotes and by generating Earth’s oxygen atmosphere. Their double-membrane architecture and the observed genome flows into them suggest a common evolutionary mechanism for their origin: an endosymbiosis between a clostridium and actinobacterium.

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Figure 1: Schematic diagrams illustrating prokaryotic symbionts.
Figure 2: An illustration of three steps required for the identification of an endosymbiont from gene flow data, and the tree of life that best fits the gene flow data.
Figure 3: A schematic diagram illustrating the prokaryotic ring of life.


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I thank C. Herbold, R. Skophammer, A. Norman and J. Servin for advice and help. This work was supported by grants from the NSF and the UCLA NASA Astrobiology Institute to J.A.L.

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Correspondence to James A. Lake.

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Lake, J. Evidence for an early prokaryotic endosymbiosis. Nature 460, 967–971 (2009).

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