Proposal for changes in the International Code of Nomenclature of Prokaryotes: granting priority to Candidatus names.

Currently, the description of taxa designated Candidatus requires gene sequences and other taxonomically relevant available information in the absence of an isolated pure culture, and Candidatus names are provisional, i.e. without formal standing in nomenclature. If gene sequences are accepted as suitable type material for the description of prokaryotic species, many taxa designated Candidatus would fulfil all the requirements in the International Code of Nomenclature of Prokaryotes for priority. Here we propose that upon acceptance of sequence data as type material, all Candidatus names published before 1 January 2020 which are otherwise in accordance with the rules of the Code will have their priority based upon their date of publication in the International Journal of Systematic and Evolutionary Microbiology, either within a paper, a list of names of Candidatus taxa, or a Validation List, unless a synonymous name already exists based upon deposition of type cultures. We further propose that modifications of the superscript 'T' be used to identify the nomenclatural types. If the type material is a culture, the superscript 'T' will continue to be used. If the type material is a sequence, the superscript 'Ts' will be used. If the type material is some other form of description, the superscript 'Td' will be used.