LETTER TO THE EDITOR. Rhodocista centenaria vs Rhodospirillum centenum: a reply to Gest and Favinger

This letter addresses confusion surrounding the nomenclature of a thermotolerant, cyst-forming anoxygenic photosynthetic bacterium. Favinger et al. (1989) originally described the organism as Rhodospirillum centenum, but did not formally submit the name for valid publication. Later, Kawasaki et al. (1992) independently designated the same organism (ATCC 43720) as Rhodocista centenaria, establishing a new genus based on 16S rDNA and chemotaxonomic data. Both names were validly published simultaneously in 1994 via Validation List no. 48 with equal priority. The author clarifies that the Bacteriological Code permits different names for the same organism when taxonomic opinion differs regarding its genus assignment. If the strain belongs to Rhodospirillum, it should be called Rhodospirillum centenum; if placed in Rhodocista, it is Rhodocista centenaria. The letter explains that Kawasaki et al. followed proper Code procedures by creating a new species name in the absence of any previously validly published name. Culture collection strain exchanges are standard practice. The author emphasizes that nomenclature rules remain neutral on taxonomic disputes, and that general scientific acceptance ultimately determines which taxonomy persists.

Key findings

• Both Rhodospirillum centenum and Rhodocista centenaria are validly published names with equal priority, received on the same day in 1994
• The same bacterial strain (ATCC 43720) can be correctly called by either name depending on whether it is classified in genus Rhodospirillum or genus Rhodocista
• Favinger et al. (1989) failed to validly publish their name according to the Bacteriological Code, allowing Kawasaki et al. (1992) to legitimately create a new species and genus name
• The Bacteriological Code governs nomenclature, not taxonomy; it remains neutral on taxonomic disputes while providing clear rules for name usage within each taxonomic classification