Proto-mitochondrion

The proto-mitochondrion is the hypothetical ancestral bacterial endosymbiont from which all mitochondria in eukaryotes are thought to descend, after an episode of symbiogenesis which created the aerobic eukaryotes.

Proto-mitochondrion
Scientific classification
Domain:
Bacteria
Phylum:
Pseudomonadota
Class:
Alphaproteobacteria
Order:
Rickettsiales (?)

Phylogeny

The phylogenetic analyses of the few genes that are still encoded in the genomes of modern mitochondria suggest an alphaproteobacterial origin for this endosymbiont, in an ancient episode of symbiogenesis early in the history of the eukaryotes. Although the order Rickettsiales has been proposed as the alphaproteobacterial sister-group of mitochondria, there is no definitive evidence as to which alphaproteobacterial group the proto-mitochondrion emerged from. Martijn et al found mitochondria are a possible sister-group to all other alphaproteobacteria.[1] The phylogenetic tree of the Rickettsidae has been inferred by Ferla et al. from the comparison of 16S + 23S ribosomal RNA sequences.[2]

Alphaproteobacteria
Magnetococcidae

Magnetococcus marinus

 
 
Caulobacteridae
 

Rhodospirillales, Sphingomonadales,
Rhodobacteraceae, Hyphomicrobiales, etc.

 
 

Holosporales

 
 
Rickettsidae
Pelagibacterales
Pelagibacteraceae

Pelagibacter

 
 

Subgroups Ib, II, IIIa, IIIb, IV and V

 
 
Rickettsiales
 

Proto-mitochondria

 
 
Anaplasmataceae
 
 
 

Ehrlichia

 
 

Anaplasma

 
 
 

Wolbachia

 
 
 

Neorickettsia

 
 
 
Midichloriaceae

Midichloria

 
Rickettsiaceae
 

Rickettsia

 
 

Orientia

 
 
 
 
 
 
 
 

Metabolism

Toni Gabaldón and Martijn Huynen (2003) reconstructed the proteome (the entire set of proteins expressed by a genome) and corresponding metabolism of the proto-mitochondrion by comparing extant alpha-proteobacterial and eukaryotic genomes. They concluded that this organism was an aerobic alpha-proteobacterium respiring lipids, glycerol and other compounds provided by the host. At least 630 gene families derived from this organism can still be found in the 9 eukaryotic genomes analyzed in the study.[3]

See also

References
  1. Martijn, Joran; Vosseberg, Julian; Guy, Lionel; Offre, Pierre; Ettema, Thijs J. G. (2018). "Deep mitochondrial origin outside the sampled alphaproteobacteria". Nature. 557 (7703): 101–105. Bibcode:2018Natur.557..101M. doi:10.1038/s41586-018-0059-5. ISSN 0028-0836. PMID 29695865. S2CID 13740626.
  2. Ferla, Mattep P.; Thrash, J. Cameron; Giovannoni, Stephen J.; Patrick, Wayne M. (2013). "New rRNA gene-based phylogenies of the Alphaproteobacteria provide perspective on major groups, mitochondrial ancestry and phylogenetic instability". PLOS ONE. 8 (12): e83383. Bibcode:2013PLoSO...883383F. doi:10.1371/journal.pone.0083383. PMC 3859672. PMID 24349502.
  3. Gabaldón, Toni; Huynen, Martijn A. (2003). "The proto-mitochondrial metabolism". Science. 301 (5633): 690. doi:10.1126/science.1085463. PMID 12893934. S2CID 28868747.
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