title: The origin of mitochondria in light of a fluid prokaryotic chromosome model.
abstract: Biologists agree that the ancestor of mitochondria was an alpha-proteobacterium. But there is no consensus as to what constitutes an alpha-proteobacterial gene. Is it a gene found in all or several alpha-proteobacteria, or in only one? Here, we examine the proportion of alpha-proteobacterial genes in alpha-proteobacterial genomes by means of sequence comparisons. We find that each alpha-proteobacterium harbours a particular collection of genes and that, depending upon the lineage examined, between 97 and 33% are alpha-proteobacterial by the nearest-neighbour criterion. Our findings bear upon attempts to reconstruct the mitochondrial ancestor and upon inferences concerning the collection of genes that the mitochondrial ancestor possessed at the time that it became an endosymbiont.
authors.affiliation: Institut für Botanik III, Heinrich-Heine Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Esser
authors.forename: William
authors.initials: W
authors.lastname: Martin
authors.forename: Tal
authors.initials: T
authors.lastname: Dagan
mesh_terms: D020561:Alphaproteobacteria / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D002875:Chromosomes / Q000235:genetics*; D019143:Evolution, Molecular; D016680:Genome, Bacterial / Q000235:genetics; D008928:Mitochondria / Q000235:genetics*; D010802:Phylogeny; D011387:Prokaryotic Cells; D012336:RNA, Ribosomal, 16S / Q000032:analysis
chemical_list: D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S