Abstract
Ongoing changes in taxonomic methods, and in the rapid development of the taxonomic structure of species assigned to the Epsilonproteobacteria have lead the International Committee of Systematic Bacteriology Subcommittee on the Taxonomy of Campylobacter and Related Bacteria to discuss significant updates to previous minimal standards for describing new species of Campylobacteraceae and Helicobacteraceae. This paper is the result of these discussions and proposes minimum requirements for the description of new species belonging to the families Campylobacteraceae and Helicobacteraceae, thus including species in Campylobacter, Arcobacter, Helicobacter, and Wolinella. The core underlying principle remains the use of appropriate phenotypic and genotypic methods to characterise strains sufficiently so as to effectively and unambiguously determine their taxonomic position in these families, and provide adequate means by which the new taxon can be distinguished from extant species and subspecies. This polyphasic taxonomic approach demands the use of appropriate reference data for comparison to ensure the novelty of proposed new taxa, and the recommended study of at least five strains to enable species diversity to be assessed. Methodological approaches for phenotypic and genotypic (including whole-genome sequence comparisons) characterisation are recommended.
Highlights
The class Epsilonproteobacteria is a phylogenetically-distinct lineage within the Proteobacteria [1] and currently contains 16 genera (Tables S1 and S2, available with the online version of this article)
Improvements in isolation, detection and taxonomic characterization methods, together with continued interest in the significance and distribution of such bacteria have resulted in the present status of the Epsilonproteobacteria – a highly diverse group of organisms containing over 100 taxa
The description of new species belonging to Campylobacteraceae or Helicobacteraceae should be based on characteristics necessary for assigning the new taxon to the genus, and on characteristics serving to differentiate the new taxon from existing taxa of the genus
Summary
The class Epsilonproteobacteria is a phylogenetically-distinct lineage within the Proteobacteria [1] and currently contains 16 genera (Tables S1 and S2, available with the online version of this article). Most taxa in the families Campylobacteraceae (namely Campylobacter, Arcobacter and Sulfurospirillum) and Helicobacteraceae (namely Helicobacter and Wolinella) appear more closely related to each other than to free-living Epsilonproteobacteria such as the Nautiliaceae [4] Their known or potential significance as pathogens, and advances in cultivation, make Campylobacter and Helicobacter the most populous genera, with many taxa sharing the same ecological niche. Phylogenetic analyses based on both 16S rRNA gene sequences (Fig. 1), and concatenated protein sequences derived from a subset of 289 conserved single-copy-number genes reveal a close relationship between Sulfurospirillum and Campylobacter [15], despite these taxa inhabiting radically different ecological niches Such observations highlight the complexities of the Epsilonproteobacteria group as a whole, and support the need for a polyphasic taxonomic approach for accurate classification
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