'Flexispira rappini' strains represent at least 10 Helicobacter taxa

'Flexispira rappini' is a provisional name given to Cram-negative, microaer ophilic, motile, spindle-shaped micro-organisms with spiral periplasmic fib res and bipolar tufts of sheathed flagella. Several investigators, includin g Kirkbride, Romero, and Archer isolated strains possessing this morphology . Previously, the phylogenetic position of three 'Flexispira rappini' strai ns was determined by 16S rRNA sequencing, which indicated that flexispira w ere members of the genus Helicobacter. As more organisms with 'F, rappini' morphology were isolated, it became apparent that there were multiple Helic obacter taxa with this distinctive morphology. The purpose of this study wa s to examine a collection of 36 'F. rappini' strains from diverse habitats by using 16S rRNA sequence analysis. The strains fell into 10 taxa, each po ssibly representing a novel Helicobacter species. Two of these flexispira t axa were previously named, by us, Helicobacter bills and Helicobacter trogo ntum. Currently, none of the flexispira taxa contains enough phenotypically and genotypically characterized strains to be formally named 'Helicobacter rappinii'.