Proposal of Holzapfeliella gen. nov. and Litorivicinus gen. nov. as replacement names for the illegitimate prokaryotic generic names Holzapfelia Zheng et al. 2020 and Litoricola Kim et al. 2007, respectively.

The prokaryotic generic names Holzapfelia Zheng et al. 2020 and Litoricola Kim et al. 2007 are illegitimate because they are later homonyms of the names Holzapfelia Cossmann 1901, an extinct genus of molluscs (Neogastropoda) and Litoricola Woodward 1873, an extinct genus of crustaceans (Arthropoda), respectively (Principle 2 and Rule 51b(4) of the International Code of Nomenclature of Prokaryotes). We therefore propose the replacement generic name Holzapfeliella with type species Holzapfeliella floricola comb. nov. and the replacement generic name Litorivicinus with replacement name Litorivicinus lipolyticus for the type species, the replacement name Litorivicinus marinus, and the family name Litorivicinaceae to replace the illegitimate name Litoricolaceae Kim et al. 2007.

Proposal of Christiangramia gen. nov., Neomelitea gen. nov. and Nicoliella gen. nov. as replacement names for the illegitimate prokaryotic generic names Gramella Nedashkovskaya et al. 2005, Melitea Urios et al. 2008 and Nicolia Oliphant et al. 2022, respectively.

The prokaryotic generic names Gramella Nedashkovskaya et al. 2005, Melitea Urios et al. 2008 and Nicolia Oliphant et al. 2022 are illegitimate because they are later homonyms of the names Gramella Kozur 1971, a genus of fossil ostracods, Melitea Péron and Lesueur 1810 (Scyphozoa, Cnidaria), Melitea Lamouroux 1812 (Anthozoa, Cnidaria), Nicolia Unger 1842, an extinct plant genus, and Nicolia Gibson-Smith and Gibson-Smith 1979 (Bivalvia, Mollusca), respectively (Principle 2 and Rule 51b(4) of the International Code of Nomenclature of Prokaryotes). For Gramella, we therefore propose the replacement generic name Christiangramia with type species Christiangramia echinicola comb. nov. and we propose the reclassification of 18 other species of Gramella in the genus Christiangramia as new combinations. In addition, we propose the replacement generic names Neomelitea with type species Neomelitea salexigens comb. nov. and Nicoliella with type species Nicoliella spurrieriana comb. nov.

Replacement of the illegitimate name Pleomorpha daqingensis (Wang et al. 2017) Montero-Calasanz et al. 2023 with the oldest legitimate name Geodermatophilus daqingensis Wang et al. 2017 and proposal to attribute this species to Petropleomorpha daqingensis (Wang et al. 2017) Li 2023 comb. nov.

The prokaryotic generic name Pleomorpha Montero-Calasanz et al. 2023 should be considered illegitimate for being a later homonym of the insect generic name Pleomorpha Saunders 1847, which contravenes Principle 2 and Rule 51b(5) of the 2022 Prokaryotic Code. The name Pleomorpha daqingensis Montero-Calasanz et al. 2023 is therefore illegitimate, and a proposal of a replacement name must be made. The author herein proposes to replace it with the oldest legitimate name Geodermatophilus daqingensis Wang et al. 2017 as requested by Rule 54 and then to attribute this species to the new combination Petropleomorpha daqingensis (Wang et al. 2017) Li 2023 comb. nov.

Proposal of Membranihabitans gen. nov. as a replacement name for the illegitimate prokaryotic generic name Membranicola Li et al. 2016.

The prokaryotic generic name Membranicola Li et al. 2016 is illegitimate because it is a later homonym of the name Membranicola Foissner, Berger and Schaumburg 1999 (Tintinnidae) (Principle 2 and Rule 51b(4) of the International Code of Nomenclature of Prokaryotes). We therefore propose the replacement generic name Membranihabitans with type species Membranihabitans marinus comb. nov.

On the status of the names Corynebacteriales Goodfellow and Jones 2015, Mycobacteriales Janke 1924 (Approved Lists 1980) and Mycobacteriales Cavalier-Smith 2002.

The name CorynebacterialesGoodfellow and Jones 2015 has been validly published by inclusion in Validation List 164, with the nomenclatural type defined as CorynebacteriumLehmann and Neumann 1896 (Approved Lists 1980). The name MycobacterialesJanke 1924 (Approved Lists 1980) appeared on the Approved Lists of Bacterial Names and is validly published, with the nomenclatural type defined as MycobacteriumLehmann and Neumann 1896 (Approved Lists 1980). The name Mycobacteriales Cavalier-Smith 2002 was validly published by inclusion in an article in the International Journal of Systematic and Evolutionary Microbiology with the nomenclatural type defined as MycobacteriumLehmann and Neumann 1896 (Approved Lists 1980). As circumscribed by the authors MycobacterialesJanke 1924 (Approved Lists 1980), Mycobacteriales Cavalier-Smith 2002 and CorynebacterialesGoodfellow and Jones 2015 all contain the genus MycobacteriumLehmann and Neumann 1896 (Approved Lists 1980), which is the nomenclatural type of MycobacterialesJanke 1924 (Approved Lists 1980). Consequently, the name CorynebacterialesGoodfellow and Jones 2015 is not the earliest validly published name, contravenes Rule 51b (1) of the International Code of Nomenclature of Prokaryotes and according to Rule 54 must be replaced. In the case of Mycobacteriales Cavalier-Smith 2002 the status of the name appears to be currently uncertain, but a solution may be in sight.

Replacement of the illegitimate genus name Hungateiclostridium Zhang et al. 2018 in Hungateiclostridium mesophilum Rettenmaier et al. 2019 by Acetivibrio Patel et al. 1980, creating Acetivibrio mesophilus (Rettenmaier et al. 2019).

A recent publication has documented the fact that when the nomenclatural types of the genera Hungateiclostridium Zhang et al. 2018 [Hungateiclostridium thermocellum (Viljoen et al. 1926) Zhang et al. 2018], Acetivibrio Patel et al. 1980 (Acetivibrio cellulolyticus Patel et al. 1980) and Herbivorax Koeck et al. 2016 (Herbivorax saccincola Koeck et al. 2016) are treated as being members of the same genus, i.e. Hungateiclostridium Zhang et al. 2018, Acetivibrio Patel et al. 1980 and Herbivorax Koeck et al. 2016 are treated as heterotypic synonyms, the name at the rank of genus to be used is Acetivibrio Patel et al. 1980 and Hungateiclostridium Zhang et al. 2018 is an illegitimate name. In a previous publication this led to the replacement of the genus name Hungateiclostridium Zhang et al. 2018 in the combinations Hungateiclostridium aldrichii (Yang et al. 1990) Zhang et al. 2018, Hungateiclostridium alkalicellulosi (Zhilina et al. 2006) Zhang et al. 2018, Hungateiclostridium clariflavum (Shiratori et al. 2009) Zhang et al. 2018, Hungateiclostridium straminisolvens (Kato et al. 2004) Zhang et al. 2018, Hungateiclostridium saccincola (Koeck et al. 2016) Zhang et al. 2018, Hungateiclostridium cellulolyticus (Patel et al. 1980) Zhang et al. 2018 and Hungateiclostridium thermocellum (Viljoen et al. 1926) Zhang et al. 2018. Given the fact that the name Hungateiclostridium Zhang et al. 2018 is illegitimate, Hungateiclostridium mesophilum Rettenmaier et al. 2019 must follow the same fate as other members of the genus and the illegitimate genus name replaced by the genus name Acetivibrio Patel et al. 1980, creating the combination Acetivibrio mesophilus (Rettenmaier et al. 2019).

The name Bradyrhizobiaceae Garrity et al. 2006 contains Nitrobacter Winogradsky 1892 (Approved Lists 1980), the nomenclatural type of the family Nitrobacteraceae Buchanan 1917 (Approved Lists 1980), is illegitimate and proposals to alter the wording of Rule 54 of the International Code of Nomenclature of Prokaryotes to clarify the fact that the family name Bradyrhizobiaceae Garrity et al. 2006 is replaced by the family name Nitrobacteraceae Buchanan 1917 (Approved Lists 1980) the only correct name.

The new name at the rank of family Bradyrhizobiaceae Garrity et al. 2006 was created to include the genera Afipia Brenner et al. 1992, Agromonas Ohta and Hattori 1985, Blastobacter Zavarzin 1961 (Approved Lists 1980), Bosea Das et al. 1996, Bradyrhizobium Jordan 1982 (the nomenclatural type), Nitrobacter Winogradsky 1892 (Approved Lists 1980), Oligotropha Meyer et al. 1994, Rhodoblastus Imhoff 2001 and Rhodopseudomonas Czurda and Maresch 1937 (Approved Lists 1980). However, Nitrobacter Winogradsky 1892 (Approved Lists 1980) is the nomenclatural type of Nitrobacteraceae Buchanan 1917 (Approved Lists 1980) a name at the rank of family that was validly published prior to the valid publication of Bradyrhizobiaceae Garrity et al. 2006 and has priority. In addition Rule 51b (1) of the International Code of Nomenclature of Prokaryotes rules that under these circumstances Bradyrhizobiaceae Garrity et al. 2006 is an illegitimate name. Illegitimate names may not be used (Rule 51a) and illegitimate names are also not taken into consideration when determining priority (Rule 23a). Nitrobacteraceae Buchanan 1917 (Approved Lists 1980) is the only correct name (Rule 23a). Despite these facts the name Bradyrhizobiaceae Garrity et al. 2006 continues to be used, perhaps because the fact that it is an illegitimate name and the consequences of that status are not fully understood. A revision of Rule 54 would also appear to be appropriate in order to further emphasise the fact that the family name Bradyrhizobiaceae Garrity et al. 2006 must be replaced by the family name Nitrobacteraceae Buchanan 1917 (Approved Lists 1980), which is the oldest legitimate name and is the only correct name that may be used for the taxon that includes Bradyrhizobium Jordan 1982 and Nitrobacter Winogradsky 1892 (Approved Lists 1980).

Arachnia propionica (Buchanan and Pine 1962) Pine and Georg 1969 (Approved Lists 1980), Propionibacterium propionicum corrig. (Buchanan and Pine 1962) Charfreitag et al. 1988 and Pseudopropionibacterium propionicum (Buchanan and Pine 1962) Scholz and Kilian 2016 and the nomenclatural consequences of changes in the taxonomy of the genus Propionibacterium.

In a recent publication dealing with the classification of species assigned to the genus Propionibacterium, evidence was presented supporting that it would be appropriate to sub-divide the genus into four genera, Propionibacterium Orla-Jensen 1909 (Approved Lists 1980) emend. Scholz and Kilian 2016, Acidipropionibacterium Scholz and Kilian 2016, Cutibacterium Scholz and Kilian 2016 and Pseudopropionibacterium Scholz and Kilian 2016. Of these genera, Pseudopropionibacterium Scholz and Kilian 2016 was proposed to contain a single species Pseudopropionibacterium propionicum (Buchanan and Pine 1962) Scholz and Kilian 2016 that is also the nomenclatural type. The nomenclatural type of Pseudopropionibacterium propionicum (Buchanan and Pine 1962) Scholz and Kilian 2016 is also the nomenclatural type of Propionibacterium propionicum corrig. (Buchanan and Pine 1962) Charfreitag et al. 1988 and Arachnia propionica (Buchanan and Pine 1962) [Pine and Georg 1969 (Approved Lists 1980)] and are consequently homotypic synonyms. Arachnia propionica(Buchanan and Pine 1962) Pine and Georg 1969 (Approved Lists 1980) was the nomenclatural type and only species placed within the genus Arachnia Pine and Georg 1969 (Approved Lists 1980). In the light of this fact, the consequences for the names Arachnia propionica (Buchanan and Pine 1962) Pine and Georg 1969 (Approved Lists 1980), Propionibacterium propionicum corrig. (Buchanan and Pine 1962) Charfreitag et al. 1988 and Pseudopropionibacterium propionicum(Buchanan and Pine 1962) Scholz and Kilian 2016 are discussed together with the correct name for the recently validly published name Pseudopropionibacterium rubrum Saito et al. 2018.