Reassessment of the taxonomy of Arcobacter cryaerophilus

Arcobacter cryaerophilus is a heterogeneous species in which two distinct subgroups have been reported. In the present study, the taxonomic status of these subgroups was reassessed using amplified fragment length polymorphism and heat shock protein 60 gene sequence analysis. The results demonstrated that A. cryaerophilus has a complex taxonomic structure, which consists of multiple cores of strains that share intermediate levels of DNA–DNA hybridisation and exhibit low levels of DNA–DNA hybridisation towards other Arcobacter species. One of these cores consisted of the majority of strains and included most subgroup 2 strains from previous studies. A. cryaerophilus subgroup 1 strains represented three distinct cores, among which the type strain occupied a distinct position. These results therefore also demonstrate that the current subgroup nomenclature in A. cryaerophilus should be abandoned, and that the type strain is genetically aberrant and poorly represents strains belonging to this species.