title: Helicobacter sp. flexispira 16S rDNA taxa 1, 4 and 5 and Finnish porcine Helicobacter isolates are members of the species Helicobacter trogontum (taxon 6).
abstract: The term 'flexispira' refers to micro-organisms with a particular morphology: fusiform-shaped with helical periplasmic fibrils and bipolar tufts of sheathed flagella. Two flexispira taxa have been formally named, Helicobacter bilis and Helicobacter trogontum, a third named species is Helicobacter aurati and eight additional 16S rRNA sequence-based flexispira taxa have been described by Dewhirst et al. (Int J Syst Evol Microbiol 50, 1781-1787, 2000) and given the provisional designation Helicobacter sp. flexispira taxa 1-5, 7, 8 and 10. In the present study, seven gastric or intestinal flexispira isolates from seven Finnish pigs originating from different farms were characterized. Morphologically, all these porcine isolates had typical flexispira morphology. Analysis of the 16S rDNA sequences of five isolates showed that they were most closely related to the sequences of flexispira taxa 4 and 5 and H. trogontum (taxon 6), but less closely related to taxa 1-3 and 8, H. bilis and H. aurati. Phenotypic characterization, analysis of RFLPs of 16S and 23S rDNAs and SDS-PAGE profiles revealed that all of the porcine isolates, reference strains of flexispira taxa 1, 4 and 5 and the type strain of H. trogontum (ATCC 700114T) had highly related characteristics that differed from those of the reference strains of taxa 2, 3 and 8 and H. bilis. Furthermore, a high DNA-DNA binding rate was found, in dot-blot hybridization studies, between the Finnish porcine strains, taxa 1, 4 and 5 reference strains and H. trogontum ATCC 700114T. In conclusion, polyphasic characterization of novel porcine flexispira isolates and previously described taxa 1, 4 and 5 reference strains showed that they all belong to a validly described species, H. trogontum, and that the taxonomy of known flexispiras is less complicated than proposed on the basis of 16S rDNA sequence analysis.
authors.affiliation: Faculty of Veterinary Medicine, Department of Food and Environmental Hygiene, PO Box 57, 00014 Helsinki University, Finland.
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Hänninen
authors.affiliation: Faculty of Veterinary Medicine, Department of Food and Environmental Hygiene, PO Box 57, 00014 Helsinki University, Finland.
authors.forename: Mari
authors.initials: M
authors.lastname: Utriainen
authors.affiliation: Faculty of Veterinary Medicine, Department of Food and Environmental Hygiene, PO Box 57, 00014 Helsinki University, Finland.
authors.forename: Irmeli
authors.initials: I
authors.lastname: Happonen
authors.affiliation: Department of Molecular Genetics, The Forsyth Institute, Boston, MA 02115, USA.
authors.forename: Floyd E
authors.initials: FE
authors.lastname: Dewhirst
mesh_terms: D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D016998:Helicobacter / Q000145:classification* / Q000235:genetics; D007413:Intestinal Mucosa / Q000382:microbiology*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000032:analysis* / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000032:analysis; D017422:Sequence Analysis, DNA; D013552:Swine
chemical_list: D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S