Nomenclature
History
The initial International Code of Nomenclature of Prokaryotes as well as early revisions did not account for the possibility of identifying prokaryotes which were not yet cultivable. Therefore, the term ''Candidatus'' was proposed in the context of a conference of theNaming
Currently, the provisional status “''Candidatus''” may be used if the following information is provided:The species name of an organism in the status of ''Candidatus'' consists of the word ''Candidatus'', followed by an either a genus name with a specific epithet, or only a genus name, or only a specific epithet. Examples include ''Candidatus'' Liberobacter asiaticum; ''Candidatus'' magnetobacterium; ''Candidatus'' intracellularis. A list of all ''Candidatus'' taxa (a ''Candidatus List'') is kept by the Judicial Commission of the ICSP in cooperation with the editorial board of the IJSEM and is updated in appropriate intervals. Once a ''Candidatus'' taxa has been cultivated successfully, the name has to be removed from this list and a new name has to be proposed in accordance with the International Code of Nomenclature of Prokaryotes. 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. 0" trial is published. The author found that 120 of the ~400 collected names would breach the Code should they become formally proposed. Common reasons are Latin errors, duplicate names, and non-Latin names. As a result, ''Candidatus Lists'' now also offer corrections for such names. Corrected names are given ''corrig.'' (for '' corrigendum'') in the authority field, with some sources going further to cite the correction (e.g. "''Ca.'' Karelsulcia" corrig. Moran ''et al.'' 2005 in Ogen ''et al.'' 2020). Each published list, starting from No. 1, covers all known ''Candidatus'' names proposed in a given time period, plus any addendum for previous periods. , the latest is ''Candidatus List No. 4'', published November 2022, covering names proposed in 2021.
Uncultivability
Environmental factors
There are several reasons for why many prokaryotic species do not grow in the lab many of which remain poorly understood. One of these reasons is the environment the species are recovered from which can be difficult to simulate in laboratory conditions. Many prokaryotes have highly specific growth requirements including the need for a specific nutrient composition, specific pH conditions, temperatures, atmospheric pressure or levels of oxygen. 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.Species interaction
Most prokaryotic species do not live alone but rather in complex communities with other species from all kingdoms of life. As a consequence, many species depend on metabolites or signaling compounds of their neighboring species for their own cell growth. 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.Genome reduction
Many instances of species interaction are ofSee also
*References
Further reading
* * * * {{Cite journal , last1 = Stackebrandt , first1 = E. , last2 = Frederiksen , first2 = W. , last3 = Garrity , first3 = G. M. , last4 = Grimont , first4 = P. A. , last5 = Kämpfer , first5 = P. , last6 = Maiden , first6 = M. C. , last7 = Nesme , first7 = X. , last8 = Rosselló-Mora , first8 = R. , last9 = Swings , first9 = J. , last10 = Trüper , first10 = H. G. , last11 = Vauterin , first11 = L. , last12 = Ward , first12 = A. C. , last13 = Whitman , first13 = W. B. , title = Report of the ad hoc committee for the re-evaluation of the species definition in bacteriology , journal = International Journal of Systematic and Evolutionary Microbiology , volume = 52 , issue = Pt 3 , pages = 1043–1047 , year = 2002 , pmid = 12054223 , doi=10.1099/ijs.0.02360-0 Bacterial nomenclature Candidatus taxa