The International Committee on Systematics of Prokaryotes (ICSP) and the International Code of Nomenclature of Bacteria are responsible for the naming of prokaryotes, including both eubacteria and archaebacteria or archaea.

In the 19th century and the first half of the 20th century, bacteriologists tried to follow the provisions of the Botanical Code of Nomenclature, because bacteria had traditionally been considered fungi, the Schizomycetes. Methods of study were, however, very different. Also, much emphasis had to be put on cultural characteristics, so that type cultures were of critical importance. Type cultures are not permitted under the Botanical Code; therefore, at the First International Congress of Microbiology in Paris in 1930, proposals were made for bacteriology to establish its own Code of Nomenclature. A committee under the able guidance of the American bacteriologist R. E. Buchanan began work on this and, at the Second Congress in London in 1936, a draft Code was presented and placed under the aegis of the International Committee for Bacteriological Nomenclature [later, the International Committee on Systematic Bacteriology (ICSB), and now, the ICSP]. Buchanan condensed the provisions for nomenclature into a few broad principles that are still valid today:

1.Names should be stable.This is assured by retaining the first name to be published, the principle of priority.

2.Names should be unambiguous.This is assured by establishing type cultures, which can be referred to whenever there is doubt about the status of a novel bacterium. Type cultures are not necessarily completely typical, but they function as indispensable points of reference.

3.Names should be necessary.This is assured by publication of descriptions of the organisms and the rejection of names that are superfluous.

Succeeding Congresses of Microbiology saw further drafting and included provision for a Judicial Commission to regulate Rules, and, where necessary, set them aside if they led to confusion. The first edition of theInternational Code of Nomenclature of Bacteria and Viruseswas published in 1958. A journal for bacterial nomenclature was started, theInternational Bulletin of Bacterial Nomenclature and Taxonomy, later theInternational Journal of Systematic Bacteriology(IJSB) and now theInternational Journal of Systematic and Evolutionary Microbiology(IJSEM). The nomenclature of viruses was later transferred to the International Congress of Virology, and virus names are effectively decided by a committee set up for that purpose.

Between 1960 and 1980, considerable problems arose because a very large percentage of published names of bacteria could not be used, due to lack of good descriptions and type cultures. It became clear that the traditional starting date for plant names of Linnaeus in 1753 was unrealistic. Under the guidance of the Australian bacteriologist V. B. D. Skerman, a decision was made to make a completely new start for nomenclature of bacteria on 1 January 1980. Lists were made of names that could be satisfactorily associated with known bacteria, and these formed the foundation document, theApproved Lists of Bacterial Names, 1980. Names not on these lists lost standing in nomenclature (though provision was made to revive old names subject to certain safeguards). All new names had to be published in the IJSB (now the IJSEM) either by being described there, or, if described elsewhere, by placing them there in Validation Lists. All bacterial names are therefore found in a single journal, and it is not necessary to search the rest of the scientific literature for them. This has proved a great advantage for bacterial taxonomy.

At the same time, the Code was completely rewritten by the British bacteriologist S. P. Lapage to make it easier to follow and to put the Rules into a more logical order. Its main sections are Rules, which are obligatory, and Recommendations, which are guides to good practice. There are sections on how to describe, name and publish on a novel bacterium, and on how to request the Judicial Commission to look into nomenclatural problems. It also lists names that have been protected (conserved) and those that must be rejected, and advises on naming of infrasubspecific divisions. The statutes of the ICSB are included.

The most recent edition of the Code is the International Code of Nomenclature of Bacteria, 1990 Revision, published in 1992 by the American Society for Microbiology. A few amendments have been made since then, and these can be found in issues of the IJSEM. A number of moves have been made to unify the nomenclature of plants, animals and bacteria, and it is hoped that, in the future, there will be progress on these lines, especially to introduce registration of all names and avoidance of synonyms in different areas of biology. These aims will be greatly assisted by on-line databases of the scientific names of all organisms.

This text was written by P. H. A. Sneath

The latest edition of the International Code of Nomenclature of Prokaryotes was presented in draft form at the Plenary Session of the Fourteenth International Congress of Bacteriology and Applied Microbiology (BAM), Montréal, 2014, together with updated lists of conserved and rejected bacterial names and of Opinions issued by the Judicial Commission. As in the past it brings together those changes accepted, published and documented by the ICSP and the Judicial Commission since the last revision published in 1990. Several new appendices have been added to this edition. Appendix 11 addresses the appropriate application of the Candidatus concept, Appendix 12 contains the history of the van Niel Prize, and Appendix 13 contains the summaries of Congresses.