Reclassification of Bifidobacterium faecale Choi et al. 2014 as a later heterotypic synonym of Bifidobacterium adolescentis Reuter 1963

Shinnosuke Okuhama; Hidenori Takahashi; Yasunori Nakayama; Akihito Endo

doi:10.1099/ijsem.0.006706

International Journal of Systematic and Evolutionary Microbiology

Volume 75, Issue 3

Research Article

Reclassification of Bifidobacterium faecale Choi et al. 2014 as a later heterotypic synonym of Bifidobacterium adolescentis Reuter 1963

Shinnosuke Okuhama¹, Hidenori Takahashi¹, Yasunori Nakayama¹ and Akihito Endo²
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¹ Department of Biolier Business, Teijin Limited, 4-3-2 Asahigaoka, Hino, Tokyo 191-8512, Japan ² Department of Nutritional Science and Food Safety, Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
*Correspondence: Shinnosuke Okuhama, [email protected] *Correspondence: Akihito Endo, [email protected]
Published: 13 March 2025 https://doi.org/10.1099/ijsem.0.006706

Abstract

Bifidobacterium faecale CU 3-7T (=JCM 19861T=KACC 17904T) was identified as a novel species primarily through phylogenetic analyses of the 16S rRNA gene, heat shock protein 60 (hsp60) and dnaJ1 sequences, and in vitro DNA–DNA hybridization (DDH) compared to Bifidobacterium adolescentis. However, genome-based taxonomic approaches have not been studied yet. This study reassessed the taxonomic relationship between B. faecale and B. adolescentis using overall genome-associated indices. The type strains of the two species possessed heterogeneous copies of the 16S rRNA gene within their genomes, with similarities below the species threshold of 98.7–99.0%. Therefore, we were unable to assess the 16S rRNA gene similarity-based taxonomic relationships. This indicated that the 16S rRNA gene is not an appropriate marker for studying the taxonomy of B. adolescentis-associated taxa. The type strains exhibited an ortho average nucleotide identity uncorrected value of 97.7% and a digital DDH value of 80.7%, indicating that they should be assigned to a single taxon. A genome-based re-assessment indicated that B. faecale should be reclassified as a later heterotypic synonym of B. adolescentis.

Received: 29/05/2024
Accepted: 20/02/2025
Published Online: 13/03/2025

Keyword(s): 16S rRNA heterogeneity , Bifidobacterium adolescentis , Bifidobacterium faecale and synonymous relationship

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Reclassification of Bifidobacterium faecale Choi et al. 2014 as a later heterotypic synonym of Bifidobacterium adolescentis Reuter 1963

Int J Syst Evol Microbiol 75, 006706 (2025); https://doi.org/10.1099/ijsem.0.006706

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International Journal of Systematic and Evolutionary Microbiology

Volume 75, Issue 3

Research Article

Reclassification of Bifidobacterium faecale Choi et al. 2014 as a later heterotypic synonym of Bifidobacterium adolescentis Reuter 1963

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