title: New insights into the phylogeny of Entamoeba species provided by analysis of four new small-subunit rRNA genes.
abstract: Sequences of small-subunit rRNA genes have been obtained for four new isolates of Entamoeba. Phylogenetic analyses give new insights into the evolution of these organisms. A novel Entamoeba from pigs in Vietnam that produces uninucleate cysts proved to be unrelated to other uninucleated cyst-producing species. Revival of the name Entamoeba suis for this organism is proposed. Instead of being related to Entamoeba polecki, it shares a recent common ancestor with the non-encysting Entamoeba gingivalis in a lineage that is basal to the tetranucleate cyst-producing clade. This suggests that species producing cysts with four nuclei are descended from an ancestor that produced cysts with a single nucleus. An Entamoeba from a horse was isolated in culture. No cysts were observed in the original stool sample but the sequence is placed unequivocally within the clade of tetranucleate cyst-producing species with no other sequences being specifically related. Revival of the name Entamoeba equi for this organism is proposed. The Entamoeba ecuadoriensis sequence was found to be the most closely related to Entamoeba histolytica and Entamoeba dispar, as predicted, despite the organism having been an environmental isolate originally assigned to Entamoeba moshkovskii. Finally, a partial E. polecki gene sequence from a pig proved to be virtually identical to that of Entamoeba struthionis from an ostrich, suggesting that the latter name is a synonym.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
authors.forename: C Graham
authors.initials: CG
authors.lastname: Clark
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
authors.forename: Farrokh
authors.initials: F
authors.lastname: Kaffashian
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
authors.forename: Blessing
authors.initials: B
authors.lastname: Tawari
authors.affiliation: National Public Health Service for Wales Aberystwyth, Bronglais Hospital, Aberystwyth, Ceredigion SY23 1ER, UK.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Windsor
authors.affiliation: Institute of Rural Sciences, University of Wales, Aberystwyth, Ceredigion SY23 3AL, UK.
authors.forename: Anke
authors.initials: A
authors.lastname: Twigg-Flesner
authors.affiliation: Institute of Rural Sciences, University of Wales, Aberystwyth, Ceredigion SY23 3AL, UK.
authors.forename: Mina C G
authors.initials: MCG
authors.lastname: Davies-Morel
authors.affiliation: Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, D-20359 Hamburg, Germany.
authors.forename: Joerg
authors.initials: J
authors.lastname: Blessmann
authors.affiliation: Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, D-20359 Hamburg, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Ebert
authors.affiliation: Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, D-20359 Hamburg, Germany.
authors.forename: Babett
authors.initials: B
authors.lastname: Peschel
authors.affiliation: Medical College, University of Hué, Hué, Vietnam.
authors.forename: An Le
authors.initials: AL
authors.lastname: Van
authors.affiliation: Institute of Rural Sciences, University of Wales, Aberystwyth, Ceredigion SY23 3AL, UK.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Jackson
authors.affiliation: National Public Health Service for Wales Aberystwyth, Bronglais Hospital, Aberystwyth, Ceredigion SY23 1ER, UK.
authors.forename: Lorna
authors.initials: L
authors.lastname: Macfarlane
authors.affiliation: Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, D-20359 Hamburg, Germany.
authors.forename: Egbert
authors.initials: E
authors.lastname: Tannich
mesh_terms: D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000032:analysis*; D004747:Entamoeba / Q000145:classification* / Q000235:genetics; D020459:Genes, rRNA / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny
chemical_list: D016054:DNA, Protozoan