- Volume 75, Issue 3, 2025

The genus Saccharopolyspora consists of Gram-positive bacteria that are found in nature. The Saccharopolyspora genus, belonging to the family Pseudonocardiaceae and order Pseudonocardiales, has shown considerable phylogenetic and taxonomic overlaps. Therefore, a phylogenetic, phylogenomic and comparative genomic investigation was conducted to elucidate the taxonomic position of four Saccharopolyspora taxa. Analysis of the 16S rRNA genes showed that the sequence similarity between the tested species ranged from 95.59 to 100%, with Saccharopolyspora hirsuta VKM Ac-666T as the type species. Moreover, the analysis of digital DNA–DNA hybridization revealed that Saccharopolyspora subtropica CGMCC 4.7206ᵀ and Saccharopolyspora thermophila JCM 10664ᵀ were 97.97% and Saccharopolyspora erythraea DSM 40517ᵀ and Saccharopolyspora spinosporotrichia JCM 10303ᵀ reached 99.9%. In addition, the average nucleotide identity values for all the combinations exceed 99%, indicating little genomic variation for these strains. Our genomic data strongly indicate the close genetic affinity between S. subtropica Wu et al. 2016 and S. thermophila Liu et al. 2001 and S. spinosporotrichia Zhou et al. 1998 and S. erythraea corrig. (Waksman 1923) Labeda 1987, which support their reclassification.

A corrigendum of this article has been published full details can be found at 10.1099/ijsem.0.007033

We present the description of the new species, Rhodococcus parequi, found during phylogenomic investigations of a global collection of strains identified as Rhodococcus (Prescottella) equi. Strain PAM 2766T was isolated from horse-breeding farm soil in Normandy, France, and was indistinguishable from R. equi based on the usual identification tests. Whole-genome phylogenetic analyses located PAM 2766T in the same Rhodococcus sublineage as R. equi, together with Rhodococcus agglutinans, Rhodococcus defluvii, Rhodococcus soli, Rhodococcus subtropicus, Rhodococcus spongiicola and Rhodococcus xishaensis. PAM 2766T is most closely related to, but sufficiently distinct from, R. equi DSM 20307 T to be considered a separate species. The average nt identity (ANI) and average aa identity (AAI) values are 88.60% and 92.35, respectively, well below the species cutoff. The PAM 2766T draft genome is ~5.3 Mb in size with 68.98% G+C mol content. PAM 2766T is strictly aerobic and non-motile and produces smooth, creamy to buff-coloured colonies very similar to those of R. equi. It phenotypically differs from the latter by the ability to grow at 5 °C, a strongly positive urease test at 24 h and specificities in the carbon and nitrogen source utilization profile as determined by phenotype microarray screens. Our data indicate that PAM 2766T belongs to a novel species, for which the name Rhodococcus parequi sp. nov. is proposed. R. parequi was avirulent in macrophage infection assays and is assumed to be non-pathogenic. The type strain is PAM 2766T (=CETC 30995T=NCTC 14987T).

The generic name Methylacidiphilum Awala et al. 2023 contravenes Rule 51b(5) of the International Code of Nomenclature of Prokaryotes (ICNP) for being a later homonym of Methylacidiphilum Ratnadevi et al. 2023, leading to the illegitimacy of Methylacidiphilum caldifontis Awala et al. 2023, Methylacidiphilaceae Awala et al. 2023 and Methylacidiphilales Awala et al. 2023. Previous taxonomic analyses revealed that the names Methylacidiphilum Awala et al. 2023 and Methylacidiphilum Ratnadevi et al. 2023 happen to be heterotypic synonyms as well, which makes sense since both the names are derived from Candidatus Methylacidiphilum. And therefore, to resolve the illegitimacy and prevent nomenclatural instability, we refrain from proposing replacement names and here call for action by the Judicial Commission to conserve Methylacidiphilum Awala et al. 2023 over Methylacidiphilum Ratnadevi et al. 2023 according to Rule 23a Note 4(1) and Rule 56b of the ICNP. The conservation of the generic name Methylacidiphilum Awala et al. 2023 will retain the usage of the family name Methylacidiphilaceae and the order name Methylacidiphilales in prokaryotic taxonomy.