Description and Naming of Candidatus Taxa

Under the rules of the International Code of Nomenclature of Prokaryotes (ICNP), names of new prokaryotic species can only be validly published after a type strain isolated in pure culture is deposited in two publicly accessible culture collections. The rules of the ICNP do not cater for the naming of the uncultivated majority of prokaryotes. In the mid-1990s, the concept of the provisional status Candidatus was developed for uncultivated organisms that could be recognized by their molecular sequences. Curated lists of Candidatus taxa are periodically published in the International Journal of Systematic and Evolutionary Microbiology. Many name corrections were proposed in these lists to replace malformed names that contravene the rules of the ICNP and its orthography appendix. An alternative code of nomenclature named the SeqCode (Code of Nomenclature of Prokaryotes Described from Sequence Data) was recently prepared to cover the nomenclature of the uncultivated majority of prokaryotes. Computer programs have been written to generate large numbers of grammatically correct genus and species names that meet the orthography standards of the ICNP and the SeqCode.