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Table 2 Summary of hypotheses and how they account for the unavoidable questions of mitochondrial origins

From: Breath-giving cooperation: critical review of origin of mitochondria hypotheses

 

Hydrogen hypothesis [12, 45]

Photosynthetic symbiont theory [36, 108]

Syntrophy hypothesis [48]

Phagocytosing archaeon theory [16]

Pre-endosymbiont hypothesis [9, 41]

Sulfur-cycling hypothesis [57]

Origin-by-infection hypothesis [57]

Oxygen detoxification hypothesis [68, 69, 103]

Eukaryotic singularity

✓

  

✓

   

✓

Lack of intermediates

✓

     

✓

 

Chimaeric nature (membrane conversion)

✓ (✓)

✓ (✓)

✓ (✓)

✓ (?)

✓ (?)

✓ (?)

✓ (?)

✓ (?)

Lack of membrane bioenergetics in host

✓

✓

✓

 

✓

   

Non-photosynthetic mitochondria

✓

✓

✓

     

Variety of mitochondria

✓

✓

✓

    

✓

Metabolism of host

✓

✓

✓

✓

✓

✓

✓

✓ (?)

Metabolism of symbiont

✓

✓

✓

?

✓

✓

✓

✓

Initial relationship

✓

✓

✓

✓ (?)

?

✓

✓

✓

Early selective advantage

✓

✓

✓

 

✓

  

✓ (untenable)

Mechanism of inclusion

✓

✓

✓

✓

✓

✓

  

Vertical transmission

      

✓

 
  1. A checkmark indicates that the hypothesis reasonably accounts for the observed facts and complies with empirical data (even if debatable). A blank cell indicates that it is unclear how the theory deals (if at all) with the given question