Valid publication of the names of forty-two phyla of prokaryotes.

After the International Committee on Systematics of Prokaryotes (ICSP) had voted to include the rank of phylum in the rules of the International Code of Nomenclature of Prokaryotes (ICNP), and following publication of the decision in the IJSEM, we here present names and formal descriptions of 42 phyla to effect valid publication of their names, based on genera as the nomenclatural types.

The International Journal of Systematic and Evolutionary Microbiology moves to 'true continuous publication' at the beginning of 2021: Proposals to emend Rule 24b (2), Note 1 to Rule 27 and Note 2 to Rule 33b of the International Code of Nomenclature of Prokaryotes.

The International Journal of Systematic and Evolutionary Microbiology (IJSEM) will move to 'true continuous publication' during the first months of 2021 to modernize the workflow and align it with the current online-only nature of the journal. In the new format, articles will be cited using an article number rather than page numbering. The article number will be the Digital Object Identifier (DOI) suffix, i.e., the last six digits of the DOI. Benefits of the new system include streamlining in-house processes, hence, reducing time and costs, and speeding up the publication time of the final 'Version of Record'. Because of the new format of the IJSEM, it is necessary to emend Rule 24b (2) and Note 1 paragraph 3 of Rule 27 of the International Code of Nomenclature of Prokaryotes (ICNP) to regulate matters of priority for papers published after January 2021. We also propose adding another example to Note 2 of Rule 33b to clarify how nomenclatural authorities of names published in the IJSEM from 2021 onward must be cited.

On neotypes and nomina nova: commentary on "Comparative analysis of Faecalibacterium prausnitzii genomes shows a high level of genome plasticity and warrants separation into new species-level taxa", by C.B. Fitzgerald et al. (BMC Genomics (2018) 19:931).

In their paper entitled "Comparative analysis of Faecalibacterium prausnitzii genomes shows a high level of genome plasticity and warrants separation into new species-level taxa" (BMC Genomics (2018) 19:931), Fitzgerald et al. proposed a neotype strain for F. prausnitzii (strain A2-165 = DSM 17677 = JCM 31915) and assigned strain ATCC 27768 = NCIMB 13872 to a newly established taxon, Faecalibacterium moorei nom. Nov. These proposals contravene the Rules of the International Code of Nomenclature of Prokaryotes (ICNP). Neotype strains can only be established following a formal proposal in the International Journal of Systematic and Evolutionary Microbiology in accordance with Rule 18c and Appendix 7 of the ICNP. A proposed neotype becomes an established neotype after 2 years, provided that no objections were submitted to the Judicial Commisson of the International Committee on Systematics of Prokaryotes within the first year following publication of the request. F. moorei as proposed by Fitzgerald et al. is a later homotypic synonym of F. prausnitzii. It cannot be a 'nom. nov.' (nomen novum): based on Rule 34a of the ICNP: this term is only used when an author transfers a species to another genus or a subspecies to another species as a new combination, but the original specific epithet cannot be used as 'comb. nov.' (combinatio nova) as a result of homonymy. Moreover, ATCC 27768 and NCIMB 13872 cannot be proposed as the type strain of F. moorei as these remain permanently associated with the type strain of F. prausnitzii unless the Judicial Commission of the ICSP will decide otherwise.

New combinations, synonymy and emendations can only be proposed based on names that were previously validly published.

Recently, articles were published in this journal in which new combinations were published based on basonyms that were not validly published at the time of submission, or a name not yet validly published was proposed as a later heterotypic synonym of another name. We here wish to remind authors and editors of the relevant rules of the International Code of Nomenclature of Prokaryotes that regulate the procedure for valid publication of names and specifically, of the fact that names in online pre-publication articles in the journal's website are not validly published.

Emendation of circumscriptions of taxa in the Lists of Changes in Taxonomic Opinion.

In the past 3 years, a large number of emendations of circumscriptions of species, subspecies and higher taxa were published outside the International Journal of Systematic and Evolutionary Microbiology (IJSEM) that only marginally modify the earlier circumscription and may not meet the requirements of Rule 35 of the International Code of Nomenclature of Prokaryotes. Thus far, these emendations were included in the Lists of Changes in Taxonomic Opinion in the IJSEM. The list editors propose to list in the future only meaningful emendations that in their opinion significantly modify the diagnostic characters or the circumscription of taxa.

Lists of names of prokaryotic Candidatus taxa.

We here present annotated lists of names of Candidatus taxa of prokaryotes with ranks between subspecies and class, proposed between the mid-1990s, when the provisional status of Candidatus taxa was first established, and the end of 2018. Where necessary, corrected names are proposed that comply with the current provisions of the International Code of Nomenclature of Prokaryotes and its Orthography appendix. These lists, as well as updated lists of newly published names of Candidatus taxa with additions and corrections to the current lists to be published periodically in the International Journal of Systematic and Evolutionary Microbiology, may serve as the basis for the valid publication of the Candidatus names if and when the current proposals to expand the type material for naming of prokaryotes to also include gene sequences of yet-uncultivated taxa is accepted by the International Committee on Systematics of Prokaryotes.

Preparation of the Validation Lists and the role of the List Editors.

Recently a number of queries were received about the ways in which requests for validation of names of taxa effectively published in journals other than the IJSEM are approved or denied and about the criteria used by the List Editors of the journal when deciding whether or not a validation request can be approved. As this process may be unclear to some authors of proposals, we would like to clarify the nature of the validation process and the role of the List Editors.

Valid publication of the names Caecibacterium and Caecibacterium sporoformans.

Descriptions of the genus Caecibacterium and its proposed type species Caecibacterium sporoformans were published in the IJSEM by Onrust et al. (Int J Syst Evol Microbiol 2017;67:4589-4594). The type strain was deposited as LMG 27730 and DSM 26959. DSM 26959 is a patent strain, and therefore the names were effectively, but not validly, published based on Rule 30(4) of the International Code of Nomenclature of Prokaryotes. The type strain of C. sporoformans is now available from the Deutsche Sammlung von Mikroorganismen und Zellkulturen as DSM 103070 and no restrictions have been placed on its distribution. We here present new descriptions of the genus and its type species so that the names can be validly published.

Proposal to modify Rules 27 and 30(3)(b) of the International Code of Nomenclature of Prokaryotes.

We propose to modify Rules 27 and 30(3)(b) of the International Code of Nomenclature of Prokaryotes so that the formal description of new taxa (the 'protologue') will include a statement about the nomenclatural type, so that this information will be linked to the name of the taxon, the derivation (etymology) of the name, and the properties of the taxon.

Why are so many effectively published names of prokaryotic taxa never validated?

Nearly half of the new names of prokaryotic taxa between the ranks of subspecies and class that were effectively published in journals other than the International Journal of Systematic and Evolutionary Microbiology (IJSEM) in the period 2014-2017 were never submitted for validation. A survey of such effectively published names that include information on the etymology of the name, a description of the taxon, and for species and subspecies generally at least one culture collection deposit, shows that for more than 150 such effectively published names per year on average, validation was never requested. To prevent further accumulation in the literature of names of prokaryotic taxa without standing in the nomenclature, we call upon authors of taxon descriptions and on the editors of the journals handling such papers to be more aware of the duty to validate effectively published names.

Proposal of the suffix -ota to denote phyla. Addendum to 'Proposal to include the rank of phylum in the International Code of Nomenclature of Prokaryotes'.

As an addendum to the earlier proposal to include the rank of phylum in the International Code of Nomenclature of Prokaryotes (Oren et al., Int J Syst Evol Microbiol 2015;65:4284-4287) we propose the suffix -ota to denote phyla, replacing the somewhat awkward -aeota. We therefore present a new draft modified version of Rule 8 of the International Code of Nomenclature of Prokaryotes and a corrected list of names of phyla to be considered for validation after approval of the proposal to include the rank of phylum in the Code.