International Committee on Systematics of Prokaryotes Frequently Asked Questions

ICSP Frequently Asked Questions (FAQ) Preamble Here we have compiled answers to questions about the activities of the International Committee on Systematics of Prokaryotes (ICSP). Please visit the pages of the ICSP website [https://the-icsp.org/] for information on specific topics and please check the “ICSP Matters” section of the International Journal of Systematic and Evolutionary Microbiology (IJSEM) to keep up to date with the committee’s activities. Executive Board of the ICSP Changelog FAQ approved in the meeting of the ICSP Executive Board (ICSP-EB) on 27th October 2022 minor changes made in subsequent e-mails and some minor formal modifications for the purpose of generating a PDF next version approved in the ICSP-EB meeting on 30th March 2023 minor additions made afterwards new section “Does the inclusion of a name in a Validation or Notification List mean that this is the name to be used for a taxon?” included in version 0.15.0 minor additions made afterwards explanation of the introduction of pro-validated published names and thus the formal regulation of Candidatus names added in version 0.17.0 The ICSP in general What is the purpose of the ICSP? The ICSP is the international body that governs the nomenclature of prokaryotes. Nomenclature is concerned with how groups of organisms (taxa) are named, whereas taxonomy is concerned with how organisms are arranged into such groups in the first place. The ICSP does not govern taxonomy. Subcommittees of the ICSP may publish minimal standards for the description of new taxa of prokaryotes but these are non-binding recommendations. Scientific journals may have their own requirements for publishing descriptions of taxa. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] 1 ICSP website [https://www.the-icsp.org/] How does the ICSP operate? The ICSP is responsible for publishing the International Journal of Systematic and Evolutionary Microbiology (IJSEM). The International Code of Nomenclature of Prokaryotes (ICNP) as well as the Validation Lists are published in the IJSEM. The Judicial Commission of the ICSP publishes Judicial Opinions on nomenclatural issues, which rule on matters of dispute submitted to it (as a ‘Request for an Opinion’). The ICSP Subcommittees on Taxonomy publish recommendations (minimal standards) for the description of new taxa in selected groups of prokaryotes. The ICSP and its subcommittees publish minutes of their meetings in the IJSEM or on the ICSP website. For details, please see the ICSP Statutes and the “ICSP Matters” section of the IJSEM. See also: IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] ICSP website [https://www.the-icsp.org/] What is the difference between the ICSP and the ICNP? The International Code of Nomenclature of Prokaryotes (ICNP) is one of the major products of the ICSP. The ICNP is not a committee but a set of General Consideration, Principles and Rules that govern the nomenclature of prokaryotes. Most ICSP decisions that affect nomenclature are decisions about emendations of the ICNP. The only other kind of ICSP decisions that affect nomenclature are decisions to ratify Judicial Opinions, but these do not override the ICNP. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Who does the ICSP represent? The ICSP has a statutory responsibility to “represent the diversity of interests of different microbiological disciplines on matters concerning the nomenclature of prokaryotes”. Its membership is defined in its Statutes. As a subsidiary of the International Union of Microbiological Societies (IUMS), each member society of the Bacteriology & Applied Microbiology (BAM) Division of the IUMS can send a delegate to the ICSP. The ICSP may also co-opt members in order to represent the international community of microbiologists more broadly. The ICSP constantly strives to increase its membership, but the outcome also depends on the willingness of societies to join the IUMS (and then nominate delegates) and on the willingness of individuals to serve on the committee. Interested members of an ICSP member society that does not have a delegate to the ICSP are encouraged to volunteer by contacting their society secretary. Alternatively, those interested in being co-opted onto the ICSP can contact the ICSP Chair or Secretary for further information. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] IUMS [http://www.iums.org/] 2 Can I join the ICSP? There are several ways to get involved. To become a voting member of the ICSP, please see above. To submit nomenclature-related proposals or to participate in ICSP debates, please see below. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] Is the ICSP democratic? Yes, it is. For example, its decisions on nomenclature are based on a majority vote of the voting members of the ICSP. For the composition of the voting members of the ICSP, see above. For the discussions that precede an ICSP decision, see below. Detailed information on the underlying regulations can be found in the ICSP Statutes. In addition, there are many matters that the ICSP does not even attempt to decide, such as taxonomy. The ICSP is authoritative on certain issues, but not authoritarian. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Is the ICSP transparent? Yes, it is. Forthcoming decisions on nomenclature are announced well in advance in the “ICSP Matters” section of the IJSEM or on the ICSP website. The reasons for each nomenclature proposal are published together with the proposal. The results of these decisions will also be announced in the IJSEM. Subcommittees of the ICSP also publish minutes of their meetings, either in the IJSEM or on the ICSP website. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Is the ICSP open? Yes, it is. Nomenclature debates are publicly announced as explained above. Nomenclature debates are also held in public prior to the subsequent ICSP vote. Previously, such debates were conducted through open e-mail exchanges. As of 2021, the ICSP will use an open channel on the Slack platform to conduct such debates. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Slack [https://icnp-revision.slack.com] Does the ICSP listen? Yes, it does. Anyone can publish formal nomenclature-related proposals in the IJSEM, such as a proposal for an emendation of the ICNP, and anyone can contribute to an open debate of the ICSP 3 and present factual arguments for or against a proposal under consideration. You do not need to be a voting member of the ICSP to influence an ICSP decision. In fact, most contributions to recent ICSP open debates have been made by participants who are not voting members of the ICSP. Numerous changes made to the ICNP throughout its existence demonstrate that it had always been possible to adapt it to new circumstances, to criticize its shortcomings and to derive improvements in its wording from such criticism. However, working on nomenclature-related regulations requires time and effort to familiarize oneself with the current wording of the ICNP and its interpretation. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Slack [https://icnp-revision.slack.com] Who can make proposals related to nomenclature? Anyone can submit proposals for nomenclature-related changes, either as proposal for modifying the ICNP, or as a Request for an Opinion to be dealt with by the Judicial Commission. For the sake of transparency, such proposals must be published in the IJSEM, as required by the ICSP Statutes. The peer review of manuscripts submitted to the IJSEM is organized by the journal. The ICSP Statutes ensure that sufficient time is allowed for discussion of such proposals before a decision is made. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Are ICSP decisions final? The processing of a particular proposal to emend the ICNP does indeed end with the vote of the voting members of the ICSP on that proposal and the subsequent publication of the result. However, alternative proposals related to rejected proposals can be made at any time in the future and may shed new light on the issues to be decided. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] The ICSP and taxonomy Does the ICSP regulate taxonomy? No. Important disciplines within systematics are classification, identification and nomenclature. The term taxonomy is often used as a synonym for systematics, although the ICNP treats taxonomy like classification, and therefore separate from nomenclature. The ICSP publishes the ICNP, and the ICNP regulates nomenclature but not classification or identification. Classification is concerned with grouping organisms; nomenclature is concerned with 4 assigning names to organisms, given the grouping. Subcommittees of the ICSP may publish minimal standards for the description of new prokaryotic taxa, but these are non-binding recommendations. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Guidelines for interpreting the ICNP [https://dx.doi.org/10.1099/ijsem.0.005782] LPSN nomenclature page [https://lpsn.dsmz.de/text/nomenclature] (not an official ICSP publication) Explanatory article [https://doi.org/10.1038/s41522-024-00494-9] (not an official ICSP publication) What is the role of the lists published in the IJSEM? For a taxon name to be recognized by the ICNP, it must be published in the IJSEM. Taxon names do not have to be proposed directly in the IJSEM; they can be published elsewhere (this is called effective publication) and then included in a Validation List to become validly published. (It should be noted that there are some basic criteria that must be met for taxon names to become validly published). The IJSEM also contains Notification Lists, which provide an overview of names published directly in the IJSEM. Lists of Changes in Taxonomic Opinion are also published in the IJSEM. These lists do not affect the status of taxon names in the ICNP, but are provided as a service to the community. Since 2025, Candidatus names still cannot be validly published, but they can be pro-validly published, and the IJSEM Candidatus Lists have become a means of determining this. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Role of the List Editors [https://doi.org/10.1099/ijsem.0.003106] Changing the role of Candidatus Lists [https://doi.org/10.1099/ijsem.0.006638] Does the ICSP approve or deny taxon names? No. The ICSP publishes the ICNP, and the ICNP regulates which names of prokaryotes have a claim to recognition under the ICNP. The ICNP also regulates which name must be used for a given taxonomic group according to its rules, and under what conditions. The IJSEM list editors can only refuse to include a name on an IJSEM Validation List if it violates the rules of the ICNP. The Judicial Commission of the ICSP may place a name on the list of rejected names, but this is done rarely, in very specific circumstances, and requires a Request for an Opinion. The ICSP does not control, nor attempt to control, the mere proposal of a taxon name. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] 5 Role of the List Editors [https://doi.org/10.1099/ijsem.0.00310 6 ] Guidelines issued by the Judicial Commission [https://dx.doi.org/10.1099/ijsem.0.005782] Does the inclusion of a name in a Validation or Notification List mean that this is the name to be used for a taxon? No. Notification Lists do not affect the status of taxon names in the ICNP anyway, but are provided as a service to the community. Inclusion of a name in a Validation List is part of the requirements for valid publication of a name whose effective publication is not in the IJSEM. Indeed, some of these names may, in time, be considered later synonyms, or it may be proposed to transfer the organisms to another genus, thus necessitating the creation of a new combination. Conversely, it may be proposed to transfer an organism back to an earlier genus and to consider the basonym or an earlier new combination to be the correct name, rather than a more recent new combination. The ICNP does not decide on such taxonomic opinions. Notification Lists indicate which names originating from an effective publication in the IJSEM itself have been validly published, but Notification Lists are neither a necessary nor a sufficient condition for a name to be validly published. Inclusion in a Validation List is a necessary condition for a name to be validly published if it originates from an effective publication outside the IJSEM. When there are several validly published and legitimate names for a taxon, the choice of the correct name depends on the circumscription, position and rank of the taxon. Rank is implicit in the taxonomic category of the name, which in turn is implicit in a validly published and legitimate name. However, circumscription and position are matters of taxonomic opinion on which the ICNP does not rule. Therefore, the inclusion of a name in a Notification or Validation list does not necessarily mean that it is the correct name for a taxon. Similarly, from 2025, Candidatus names may be pro-validly published, but if so, this does not necessarily mean that they are the pro-correct names for the taxa concerned. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Role of the List Editors [https://doi.org/10.1099/ijsem.0.00310 6 ] Guidelines issued by the Judicial Commission [https://dx.doi.org/10.1099/ijsem.0.005782] Article explaining the term “correct name” [https://doi.org/10.1099/00207713-49-3-1313] (not an official ICSP publication and slightly outdated) More recent explanatory article [https://doi.org/10.1038/s41522-024-00494-9] (not an official ICSP publication) LPSN FAQ page [https://lpsn.dsmz.de/text/faq#why-and-how-does-lpsn-assign-the-statuscorrect-name] (not an official ICSP publication) LPSN Glossary [https://lpsn.dsmz.de/text/glossary#correct-name] (not an official ICSP publication) Introducing pro-validly published names [https://doi.org/10.1099/ijsem.0.006638] 6 Does the ICSP propose taxon names? No. Taxon names are proposed by individual taxonomists. Some members of the ICSP are also active in taxonomy, but when doing so they act as individual taxonomists and not as members of the ICSP. Having different roles does not in itself create a conflict of interest. Rather, an active taxonomist may be more likely to become aware of nomenclatural issues and report them to the ICSP. The ICSP regulates nomenclature mainly through the publication of the ICNP, and the ICNP is explicitly dedicated to ensuring taxonomic freedom. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Clarification of the role of the ICSP [https://doi.org/10.1038/s41579-022-00706-z] Does the ICSP hinder anyone proposing taxon names? No. Scientific journals may have their own requirements for publishing descriptions of microbial taxa but, with the exception of the IJSEM, these journals are independent of the ICSP. The ICSP publishes the ICNP, and the ICNP regulates which taxon names have claim to recognition under its rules. However, this does not mean that a taxon name that does not (yet) have claim to recognition under the ICNP cannot be proposed. On the contrary, the proposal of a taxon name in a publication is a prerequisite for obtaining a claim to recognition under the ICNP. The ICSP does not control, nor does it attempt to control, the mere proposal of a taxon name. See also: ICSP Statutes [https://doi.org/10.1099/ijsem.0.006918] ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Clarification of the role of the ICSP [https://doi.org/10.1038/s41564-022-01167-z] Does the ICSP replace taxon names by others? No. Taxon names intended to replace other taxon names may be proposed by individual taxonomists. In most cases, this is done by proposing new combinations to reflect the placement of a species in a different genus (or, less commonly, the placement of a subspecies in a different species). Users of taxon names are free to use either the older or the newer name in such cases, depending on their taxonomic view of the classification. The same applies to databases, i.e. curators can choose which name they prefer. Even if the proposal of a taxon name is intended to replace a name that does not conform to the ICNP, this is done by individual taxonomists, not by the ICSP. The ICSP does not control or attempt to control the adoption of taxon names by third parties, although it may attempt to clarify which names are consistent with the ICNP and which are not. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Guidelines issued by the Judicial Commission [https://dx.doi.org/10.1099/ijsem.0.005782] 7 Does the ICSP change the spelling of taxon names? No. The ICNP regulates what orthographic or grammatical corrections can be made to the spelling of a taxon name, and by whom. Corrections to the spelling of a taxon name are proposed by individual taxonomists or by the IJSEM List Editors. The ICNP provides clarity as to whether such corrections are in accordance with its rules. In case of doubt about a spelling, a Request for an Opinion can be sent to the Judicial Commission of the ICSP. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] IJSEM [https://www.microbiologyresearch.org/content/journal/ijsem] Guidelines for writing a Request for an Opinion [https://dx.doi.org/10.1099/ijsem.0.005782] Are nomenclature-related regulations published by the ICSP impractical or confusing? No. The ICNP is very similar to the ICNafp (International Code of Nomenclature for algae, fungi, and plants, also known as the Botanical Code), from which it is historically derived. Most of the key concepts are the same, including valid publication, legitimacy and correctness of names. The ICZN (International Code of Zoological Nomenclature) uses different terms, but shares many concepts with the ICNafp and ICNP. A large number of names have been validly published (ICNafp, ICNP) or made available (ICZN) under all three codes and all three codes regulate the use of these names. Most microbiologists come into contact with prokaryotic taxon names before they are aware of the actual rules that govern the creation and use of these names. Users of taxon names may therefore make inferences about nomenclature based on how certain databases, non-official publications or other sources handle taxon names. If such inferences later come into conflict with the actual rules, this does not mean that the actual rules are confusing or otherwise deficient. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] ICNafp [https://www.iapt-taxon.org/nomen/main.php] ICZN [https://code.iczn.org] Guidelines issued by the Judicial Commission [https://dx.doi.org/10.1099/ijsem.0.005782] Is knowledge of Latin required to propose taxon names? No. In the ICNP, taxon names are treated as Latin, but this does not mean that taxon names have to correspond in part or in full to known Latin words. In the ICNP, it must be possible to treat a taxon name as if it were Latin, but a taxon name can also be formed arbitrarily. There are a number of fairly simple approaches to taxon name formation that can be used by anyone. Instead of learning Latin, it is almost always sufficient to study the relevant sections of the ICNP, such as Appendix 9, to form taxon names according to the ICNP. Moreover, there are many commonly used and wellknown Latin or Greek components of taxon names that can easily be reused by any taxonomist. Of course, if someone wanted to express something sophisticated in a taxon name, a deeper knowledge of Latin (or Greek) would be required. But this is natural, and the ICSP does not force anyone to be 8 sophisticated in this respect. In addition, the IJSEM has nomenclature reviewers who can give expert advice on naming. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Forming names [https://dx.doi.org/10.1093/femsle/fnaa096] Nomenclature reviewers [https://www.microbiologyresearch.org/content/journal/ijsem? page=editorial-board] LPSN etymology page [https://lpsn.dsmz.de/text/etymology] (not an official ICSP publication) Why are taxon names treated like Latin? One reason for using Latin word components is that these components do not change in meaning, as Latin is a (nearly) dead language. Forming all taxon names in such a way that they have a Latin "look and feel", even if the names are actually formed arbitrarily, has the even greater advantage that most taxon names are fairly easily recognised as taxon names even if you have not seen them before. Being able to easily distinguish taxon names from the surrounding text is very helpful when dealing with scientific literature. Last but not least, all three major nomenclature codes (botanical code - ICNafp, zoological code - ICZN, microbiological code - ICNP) treat taxon names as Latin, and have done so for more than a century. For this reason, consistency alone dictates that this practice should continue. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] ICNafp [https://www.iapt-taxon.org/nomen/main.php] ICZN [https://code.iczn.org] What is a nomenclatural type good for? Taxon names proposed in accordance with the ICNP have a nomenclatural type. Although called "type", the nomenclatural type need not be typical or representative of its taxon. The purpose of a nomenclatural type is to be permanently attached to a taxon name. (Elsewhere the nomenclatural type is called a "name-bearing type" or "nominifer", which fits well). This is necessary to clarify which name should be used in certain situations and to reflect certain taxonomic views, e.g. when a taxon is split or two taxa are merged. The use of nomenclatural types is particularly elegant in the case of taxa above the rank of genus, whose names are derived from the name of their nomenclatural type (or the nomenclatural type of their nomenclatural type). Thus, the regularly formed name of each taxon above genus rank directly indicates the only genus that is guaranteed to be contained within the taxon above genus rank. In the case of the ICNP, since January 2001, the nomenclatural type of a species or subspecies must be a strain available to others for taxonomic study, which is important for replication and comparison purposes. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] 9 Judicial Opinion 129 [https://doi.org/10.1099/ijsem.0.006064] Did names of archaeal phyla ever have the suffix -archaeota, or should they have that suffix? No. Names like “Crenarchaeota” may indeed give the impression that they have an -archaeota suffix. But this is not the case. The name is composed as follows: Cren- (stem of krênê when Latinized, Greek κρήνη, genitive κρήνης) + archae- (stem of archaeum, originally from Greek ἀρχαῖος) + -ota (adjectival suffix). So -archaeota is not a suffix; -ota is. Furthermore, suppose you wanted to implement the suffix -archaeota for archaeal phyla and then derive a phylum name from, say, a type genus called Halarchaeum. This would yield Halarchaearchaeota (sic), hardly a pleasant result. One must consider that the archaecomponent of names such as “Crenarchaeota” is not part of a suffix, i.e. -archaeota is not actually a suffix but the penultimate component of the taxon name plus the actual suffix. If a genus name ending in -archaeum was chosen as type genus, then this would already result in phylum name ending in -archaeota. It is not necessary to change the standardized ending for archaeal phylum names to achieve this effect. In general, it is unwise to encode taxonomic affiliation with a higher-ranked taxon in a name above species rank. The regular derivation of names above genus rank in the ICNP works in the opposite direction: they are derived from the name of a genus. Since that genus is the nomenclatural type (or the nomenclatural type of the nomenclatural type), it is guaranteed to be permanently associated with the taxon for which it serves directly or indirectly as type, whether treated as the correct name or as a synonym. In contrast, the assignment of a taxon to a higher taxon, such as the assignment of the class Deltaproteobacteria to “Proteobacteria” (Pseudomonadota), is a matter of taxonomic opinion. Since many taxonomists today place Deltaproteobacteria in a different phylum from that to which Alpha-, Betaor Gammaproteobacteria are assigned, the situation may be confusing (although changing the names would be even more unfortunate). Such problems only occur because the name of the superordinate taxon has been encoded in the name of the subordinate taxon. This way of forming names is no longer allowed under the ICNP. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Judicial Opinion 116 [https://dx.doi.org/10.1099/ijsem.0.005481] Kingdoms “Crenarchaeota” and “Euryarchaeota” [https://doi.org/10.1073/pnas.87.12.4576] (not an official ICSP publication) Overview on regular endings of names above genus rank and their origin [https://dx.doi.org/10.1099/ijsem.0.005650] (not an official ICSP publication) Judicial Opinion 129 [https://doi.org/10.1099/ijsem.0.006064] Does the name Actinomycetota indicate fungi? Not really. The validly published name Actinomycetota denotes the phylum that was previously known as “Actinobacteria” – a problematic name because it is not derived from the name of its nomenclatural type and because it is eponymous with the validly published (albeit illegitimate) name of a class. The name Actinomycetota is derived from Actinomyces, and the -myces component of this genus name does indicate a fungus. However, we suspect that most microbiologists are well 16 aware that genera such as Actinomyces and Streptomyces are bacteria. While the use of the -myces component in prokaryotic names is no longer permitted by the ICNP (2022 Revision), there are historical reasons for the occurrence of these names. The phylum name Actinomycetota is also a much better fit than “Actinobacteria” with the validly published and legitimate names used at the ranks of class, order, family and genus: Actinomycetes, Actinomycetales, Actinomycetaceae, Actinomyces. Replacing them by names not indicating fungi has no basis in the ICNP and would cause far more problems than the current names themselves. In the botanical code (ICNafp) names of fungal phyla have the suffix -mycota. Deriving a phylum name from Actinomyces under this code would result in Actinomycetomycota or Actinomycota. Confusion is therefore unlikely. See also: ICNP [https://dx.doi.org/10.1099/ijsem.0.000778] Introduction of phylum category [https://dx.doi.org/10.1099/ijsem.0.004851] Explanatory article [https://doi.org/10.1038/s41522-024-00494-9] (not an official ICSP publication) Judicial Opinion 119 [https://dx.doi.org/10.1099/ijsem.0.005481] ICNafp [https://www.iapt-taxon.org/nomen/main.php] 17