From >2,000 bacterial isolates cultured at 14Β°C from Midui, Hailuogou, Laigu, Renlongba, Zepu and Gawalong glaciers (Tibetan Plateau, collected 2009β2016), the authors delineated 15 novel Janthinobacterium species (e.g., J. algoris, J. darwini, J. woesei, J. violaceum, J. amylolyticum), roughly tripling the genus' validly named species count .
The taxonomic case is strong: all 15 pairwise ANI values fell below 95%; dDDH values against related type strains ranged 22.2β64.0% (threshold <70%); four strains matched glacial MAGs/isolates from India and the Alps at ANI β₯96%, suggesting conserved glacial species. Genome quality was high (100% completeness, 0β1.4% contamination; sizes 4.90β6.44 Mb; GC 60.8β63.3%) . The authors candidly note that 16S rRNA NJ trees showed low bootstrap supportβan acknowledged limitation correctly addressed by phylogenomics, consistent with the known poor resolution of 16S in rapidly radiating Burkholderiaceae .
All reported dDDH values sit far below the 70% species boundary, supporting species distinctness with a comfortable margin.
Each species rests on a single type strain, so intra-species genomic plasticity is uncharacterized; cultivation bias (R2A/PYG at 14Β°C) restricts inferred diversity; and ecological/functional roles (e.g., violacein production, which shows antimicrobial and anti-cancer activity in related taxa ) remain unexplored in the new species. ANI/dDDH thresholds are themselves debated in prokaryotic taxonomy. Falsification would require any strain showing ANI β₯95% or dDDH β₯70% with a named species. Confidence: high for species distinctness (strong genomic data), moderate for ecological claims.
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