New higher rank taxa include five families (Luteibaculaceae, Parvicellaceae, Salibacteraceae, Vicingaceae and Weeksellaceae) and 43 genera (‘Paracrocinitomix’, Putridiphycobacter, ‘Taishania’, Abyssalbus, Aegicerativicinus, Aestuariimonas, ‘Aggregatimonas’, Amniculibacterium, Antarcticibacterium, ‘Ascidiaceibacter’, ‘Avrilella’, Christiangramia, ‘Citreibacter’, Cochleicola, ‘Constantimarinum’, ‘Coraliitalea’, Haloflavibacter, ‘Halomarinibacterium’, Luteirhabdus, Mesohalobacter, Paramesonia, Pareuzebyella, Patiriisocius, Paucihalobacter, Pelagihabitans, Pontimicrobium, Poritiphilus, Pseudalgibacter, Pukyongia, ‘Rasiella’, Sinisalibacter, Spodiobacter, ‘Spongiibacterium’ (currently contains only the orphan species S. fuscum), Ulvibacterium, Urechidicola, Wocania, Parvicella, Croceimicrobium, Thermaurantimonas, Acidiluteibacter, Vicingus, Faecalibacter and Frigoriflavimonas). New species and species that were transferred to another genus number 480 (across 114 genera out of the 200 belonging to Flavobacteriia); 63 species names still require official validation as of the time of the meeting. Reclassification of species occurred in the genera Algibacter, Arcticiflavibacter, Arenitalea, Chryseobacterium, Epilithonimonas, Flagellimonas, Flavihalobacter, Flaviramulus, Flavobacterium, Formosa, Ichthyenterobacterium, Kaistella, Maripseudobacter, Mesoflavibacter, Muricauda, Soonwooa, Spongiibacterium, Ulvibacter and Vitellibacter. For example, the taxonomy of the genus Chryseobacterium has been redefined using genome-based taxonomy [4] and some of its species have been assigned to the genera Epilithonomonas, Kaistella, Halpernia and Soonwooa. The name Christiangramia is the replacement for the genus Gramella owing to it already being the name for fossil ostracods, described originally in 1971 [5]. The genus Flavobacterium is remarkable in that its number of species has now swelled to more than 300. Two Candidatus genera are listed in the LPSN, called Candidatus ‘Prosiliicoccus’ and Candidatus ‘Merdimorpha’. Though not listed in the LPSN, Candidatus ‘Marisimplicoccus’, Candidatus ‘Marivariicella’, Candidatus ‘Maricapacicella’ and Candidatus ‘Arcticimaribacter’ were defined to represent genus-level groups within a major clade of uncultured marine bacteria designated the NS5 clade, located within the family Flavobacteriaceae [6]. Further details are mentioned in the LPSN.

The sphingobacteria now include three new genera named Albibacterium, Daejeonella and Pararcticibacter as well as 106 new species names described across 10 genera. Most new species belong to the species rich genera, Mucilaginibacter, Pedobacter and Sphingobacterium. Species reclassification mainly affected genus Pedobacter in which eight species were reclassified as Daejeonella (seven species) or Albibacterium (one species). The type species of Pseudosphingobacterium (P. domesticum) was also transferred to the genus Olivibacter.

A total of 21 new genus names were described including Agriterribacter, Aurantisolimonas, Deminuibacter, Edaphocola, Flavipsychrobacter, ‘Foetidibacter’, ‘Ginsengibacter’, Gynurincola, ‘Hanamia’, Ilyomonas, Limnovirga, ‘Longitalea’, Mucibacter, Nemorincola, Paracnuella, Paraflavisolibacter, Paraflavitalea, Parapseudoflavitalea, Phnomibacter, Pinibacter and ‘Pseudocnuella’. Furthermore, 85 new species names (across 40 genera) were described or were created due to reclassification. Reclassification resulted in the type species of Asinibacterium, Crenotalea, Filimonas, Pseudobacter and Vibrionimonas being merged into other genera that had priority due to an earlier publication date. More details are provided by the LPSN.

A total of eight new family names were created between 2018–2023 mainly due to reclassification of species on the basis of genome-based taxonomy. These include Cesiribacteraceae, Fulvivirgaceae, Mangrovivirgaceae, Marivirgaceae, Raineyaceae, Reichenbachiellaceae, Roseivirgaceae and Thermoflexibacteraceae. In addition, 22 new genus names were described: Arthrospiribacter, Cognataquiflexum, Pararhodonellum, Penaeicola, Pleomorphovibrio, Aquirufa, Arundinibacter, ‘Chryseosolibacter’, Chryseotalea, ‘Dawidia’, Edaphorhabdus, Sandaracinomonas, Tellurirhabdus, ‘Marinigracilibium’, Xanthovirga, Parachryseolinea, Pseudochryseolinea, Botryobacter, Sabulibacter, Raineya, ‘Fibrivirga’, Marinilongibacter and Rhodoflexus. The genera Fabibacter and Fabivirga were also reclassified into the genus Roseivirga. Species description was highly active with more than 190 new species described across 48 genera, including major expansions of the genera Hymenobacter (51 new species) and Spirosoma (24 new species).

The saprospiria expanded only by four genera since 2018, including Portibacter, Flavilitoribacter, Neolewinella and Membranihabitans. The genera Flavilitoribacter and Neolewinella were created by the reclassification of most species of the genus Lewinella, which now includes currently only its type species L. cohaerens. In addition, the genus Membranicola was merged with Membranihabitans. Only two truly new saprospiria species were described from marine samples, Flavilitoribacter nigricans and Membranihabitans marinus. This lack of species descriptions suggests the saprospiria are challenging to culture. As a likely consequence several Candidatus taxa have been described and which are listed in the LPSN. These include Candidatus ‘Brachybacter’, Candidatus ‘Defluviibacterium’, Candidatus ‘Opimibacter’, Candidatus ‘Parvibacillus’ and Candidatus ‘Vicinibacter’ and are in addition to what has been named by Pallen and colleagues.

Amongst members of class Bacteroidia able to utilize oxygen (Marinifilaceae, Marinilabiliaceae, Prolixabacteraceae) a number of new genera were described since 2018 including Aquipluma, Maribellus, Labilibaculum and Puteibacter. The genus Breznakibacter was also created to accommodate the long misclassified species [Cytophaga] xylanolyticus while the genus Labilibacter was merged into the genus Saccharicrinis. This still leaves the species Labilibacter sediminis as an orphan species. Ignoring new combinations collectively 25 species were created across the facultatively anaerobic members of Bacteroidia.

A proposal was made to combine the genera Fodinibius and Aliifodinibius; however, as indicated on the LPSN at the time of the Subcommittee meeting, the resulting nomenclature remains to be validated. A new family called ‘Cyclonatronaceae’ was defined containing the genera ‘Cyclonatronum’ and ‘Natronogracilivirga’, isolated from hypersaline soda lakes. Another soil-derived genus called Halalkalibaculum which possesses a single species was also described separately. A further six species have been proposed for the genera Fodinibius, Aliifodinibius, Gracilimonas and Rhodohalobacter.

This former clade of Bacteroidota shows continual slow expansion. The genus Rhodocaloribacter was added to the family Rhodothermaceae. The genus Rhodothermus acquired one additional species while in the case of Salinibacter five species were described since 2018. The genus Salinivenus (belonging to family Salinibacteraceae) and its two species was validly described in 2018. A new genus called Roseithermus was described within the family Salisaetaceae while another member of this family, the genus Natronotalea, acquired an additional species.