title: Phylogenomic evidence for a myxococcal contribution to the mitochondrial fatty acid beta-oxidation.
abstract: BACKGROUND
  The origin of eukaryotes remains a fundamental question in evolutionary biology. Although it is clear that eukaryotic genomes are a chimeric combination of genes of eubacterial and archaebacterial ancestry, the specific ancestry of most eubacterial genes is still unknown. The growing availability of microbial genomes offers the possibility of analyzing the ancestry of eukaryotic genomes and testing previous hypotheses on their origins.
  
  
  RESULTS
  Here, we have applied a phylogenomic analysis to investigate a possible contribution of the Myxococcales to the first eukaryotes. We conducted a conservative pipeline with homologous sequence searches against a genomic sampling of 40 eukaryotic and 357 prokaryotic genomes. The phylogenetic reconstruction showed that several eukaryotic proteins traced to Myxococcales. Most of these proteins were associated with mitochondrial lipid intermediate pathways, particularly enzymes generating reducing equivalents with pivotal roles in fatty acid β-oxidation metabolism. Our data suggest that myxococcal species with the ability to oxidize fatty acids transferred several genes to eubacteria that eventually gave rise to the mitochondrial ancestor. Later, the eukaryotic nucleocytoplasmic lineage acquired those metabolic genes through endosymbiotic gene transfer.
  
  
  CONCLUSIONS
  Our results support a prokaryotic origin, different from α-proteobacteria, for several mitochondrial genes. Our data reinforce a fluid prokaryotic chromosome model in which the mitochondrion appears to be an important entry point for myxococcal genes to enter eukaryotes.
authors.affiliation: Neurometabolic Diseases Laboratory, Institut d'Investigació Biomèdica de Bellvitge (IDIBELL), L'Hospitalet de Llobregat, Barcelona, Spain.
authors.forename: Agatha
authors.initials: A
authors.lastname: Schlüter
authors.forename: Iñaki
authors.initials: I
authors.lastname: Ruiz-Trillo
authors.forename: Aurora
authors.initials: A
authors.lastname: Pujol
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D056890:Eukaryota / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism*; D023281:Genomics; D053858:Metabolic Networks and Pathways; D008928:Mitochondria / Q000235:genetics*; D008954:Models, Biological; D009231:Myxococcales / Q000235:genetics*; D010084:Oxidation-Reduction; D010802:Phylogeny; D011506:Proteins / Q000235:genetics
chemical_list: D000214:Acyl Coenzyme A; D005227:Fatty Acids; D011506:Proteins