- Volume 71, Issue 10, 2021

After the International Committee on Systematics of Prokaryotes (ICSP) had voted to include the rank of phylum in the rules of the International Code of Nomenclature of Prokaryotes (ICNP), and following publication of the decision in the IJSEM, we here present names and formal descriptions of 42 phyla to effect valid publication of their names, based on genera as the nomenclatural types.

Parvularcula flava was proposed as a novel member of genus Parvularcula in 2016. Some time earlier, Aquisalinus flavus has been proposed as a novel species of a novel genus named Aquisalinus . When comparing the 16S rRNA gene sequences of type strains P. flava NH6-79T and A. flavus D11M-2T, they showed 97.9 % sequence identity, much higher than the sequence identities 92.7–94.3 % between P. flava NH6-79T and type strains in the genus Parvularcula , indicating that the later proposed novel taxon Parvularcula flava need reclassification. The phylogenetic trees based on 16S rRNA gene sequences and genome sequences both showed that P. flava NH6-79T and A. flavus D11M-2T formed a separated branch away from strains in the genera Parvularcula , Marinicaulis and Amphiplicatus . The average amino acid identity and average nucleotide identity values of P. flava NH6-79T and A. flavus D11M-2T were 87.9 and 85.0 %, respectively, much higher than the values between P. flava NH6-79T and other closely related type strains (54.3 %–58.1 % and 68.6–70.4 %, respectively). P. flava NH6-79T and A. flavus D11M-2T also contained summed feature 8 (C18 : 1  ω6c and/or C18 : 1  ω7c) and C16 : 0 as major fatty acids, distinguishing them from other closely related taxa. Based on the results of the phylogenetic, comparative genomic and phenotypic analyses, Parvularcula flava should be reclassified as Aquisalinus luteolus nom. nov. and the description of genus Aquisalinus is emended.

Hanstruepera crassostreae L53T was compared with Pseudobizionia ponticola MM-14T to examine the taxonomic relationship between the two type strains. The 16S rRNA gene sequence of H. crassostreae L53T had complete similarity (100.0%) to that of P. ponticola MM-14T. The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that the two strains formed a tight cluster within the genus Pseudobizionia . Draft genomic comparison between the two strains revealed an average nucleotide identity of 96.9 % and a digital DNA–DNA hybridization estimate of 75.3±2.8 %, strongly indicating that the two strains represented a single species. In addition, neither strain displayed any striking difference in metabolic, physiological or chemotaxonomic features. Therefore, we propose that Hanstruepera crassostreae is a later heterotypic synonym of Pseudobizionia ponticola .

The taxonomic positions of members within the family Pseudonocardiaceae were assessed based on phylogenomic trees reconstructed using core-proteome and genome blast distance phylogeny approaches. The closely clustered genome sequences from the type strains of validly published names within the family Pseudonocardiaceae were analysed using overall genome-related indices based on average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values. The family Pseudonocardiaceae consists of the type genus Pseudonocardia , as well as the genera Actinoalloteichus , Actinocrispum , Actinokineospora , Actinomycetospora , Actinophytocola , Actinopolyspora , Actinorectispora , Actinosynnema , Allokutzneria , Allosaccharopolyspora gen. nov., Amycolatopsis , Bounagaea , Crossiella , Gandjariella , Goodfellowiella , Haloactinomyces , Haloechinothrix , Halopolyspora , Halosaccharopolyspora gen. nov., Herbihabitans , Kibdelosporangium , Kutzneria , Labedaea , Lentzea , Longimycelium , Prauserella , Saccharomonospora , Saccharopolyspora , Saccharothrix , Salinifilum , Sciscionella , Streptoalloteichus , Tamaricihabitans , Thermocrispum , Thermotunica and Umezawaea . The G+C contents of the Pseudonocardiaceae genomes ranged from 66.2 to 74.6 mol% and genome sizes ranged from 3.69 to 12.28 Mbp. Based on the results of phylogenomic analysis, the names Allosaccharopolyspora coralli comb. nov., Halosaccharopolyspora lacisalsi comb. nov. and Actinoalloteichus caeruleus comb. nov. are proposed. This study revealed that Actinokineospora mzabensis is a heterotypic synonym of Actinokineospora spheciospongiae , Lentzea deserti is a heterotypic synonym of Lentzea atacamensis , Prauserella endophytica is a heterotypic synonym of Prauserella coralliicola , and Prauserella flava and Prauserella sediminis are heterotypic synonyms of Prauserella salsuginis . This study addresses the nomenclature conundrums of Actinoalloteichus cyanogriseus and Streptomyces caeruleus as well as Micropolyspora internatus and Saccharomonospora viridis .