title: Planctomycetes and eukaryotes: a case of analogy not homology.
abstract: Planctomycetes, Verrucomicrobia and Chlamydia are prokaryotic phyla, sometimes grouped together as the PVC superphylum of eubacteria. Some PVC species possess interesting attributes, in particular, internal membranes that superficially resemble eukaryotic endomembranes. Some biologists now claim that PVC bacteria are nucleus-bearing prokaryotes and are considered evolutionary intermediates in the transition from prokaryote to eukaryote. PVC prokaryotes do not possess a nucleus and are not intermediates in the prokaryote-to-eukaryote transition. Here we summarise the evidence that shows why all of the PVC traits that are currently cited as evidence for aspiring eukaryoticity are either analogous (the result of convergent evolution), not homologous, to eukaryotic traits; or else they are the result of horizontal gene transfers.
authors.affiliation: Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland. james.o.mcinerney@nuim.ie
authors.forename: James O
authors.initials: JO
authors.lastname: McInerney
authors.forename: William F
authors.initials: WF
authors.lastname: Martin
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Koonin
authors.forename: John F
authors.initials: JF
authors.lastname: Allen
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Galperin
authors.forename: Nick
authors.initials: N
authors.lastname: Lane
authors.forename: John M
authors.initials: JM
authors.lastname: Archibald
authors.forename: T Martin
authors.initials: TM
authors.lastname: Embley
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D005075:Biological Evolution; D002467:Cell Nucleus / Q000502:physiology; D002689:Chlamydia / Q000145:classification / Q000166:cytology* / Q000235:genetics / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000502:physiology; D056890:Eukaryota / Q000145:classification / Q000166:cytology* / Q000235:genetics / Q000502:physiology; D022761:Gene Transfer, Horizontal; D008928:Mitochondria / Q000235:genetics / Q000502:physiology; D009685:Nuclear Envelope / Q000502:physiology; D010802:Phylogeny; D061328:Planctomycetales / Q000145:classification / Q000166:cytology* / Q000235:genetics / Q000502:physiology; D061327:Verrucomicrobia / Q000145:classification / Q000166:cytology* / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins