Candidatus

; Latin for "candidate of Roman office") is used to name prokaryotic taxa that are well characterized but yet-uncultured.

[2] Owing to rising numbers of Candidatus taxa associated with ongoing advances of sequencing technologies, the ICSP adopted the International Code of Nomenclature of Prokaryotes in 1996 by adding an appendix for Candidatus taxa[3] (Appendix 11 in the most recent version[4]).

[citation needed] Although the 1994 proposal and the later Code call for a Candidatus List to be maintained, work on curating names did not start until 2017, when a "No.

[10] The Code of Nomenclature of Prokaryotes Described from Sequence Data (SeqCode) of 2022 standardizes the publication of names in a system separate from the ICNP.

[12] The SeqCode team initially wished to simply amend the ICNP to add such a system, but ICSP rejected the petition, necessitating the creation of a separate code.

A genome sequence is more stable than a cell culture, which can be (and has been) lost and are subject to genetic drift under the different selective pressure of the lab.

[14] Most commercially available growth media and incubation protocols poorly met these requirements making a comprehensive habitat assessment necessary in order to successfully isolate the bacteria of interest from environmental samples.

The identification of the required substances can be challenging but once identified a co-cultivation or addition of the specific compound can be used to potentially cultivate the species of interest.

This frequently affects genes for DNA repair and transcriptional regulation which makes it difficult to cultivate these organisms outside their host.