# Ten novel psychrophilic Flavobacterium species from Tibetan Plateau glaciers define a cryospheric lineage with global cold-origin relatives

## TL;DR

Scientists discovered ten new cold-loving Flavobacterium species from Tibetan glaciers, which form a unique group related to other cold-dwelling bacteria worldwide.

## Contribution

The discovery of ten novel Flavobacterium species and the identification of a global cryospheric lineage through phylogenomic analysis.

## Key findings

- Twenty-three novel psychrophilic Flavobacterium strains were isolated from Tibetan glaciers.
- The ten novel species form a distinct 'Cryospheric Lineage' clade with global cold-origin relatives.
- Phylogenomic and genomic analyses confirmed these species as distinct based on low ANI and dDDH values.

## Abstract

Twenty-three novel psychrophilic bacteria, represented by the type strains LB2P44T, LB2P6T, LB1P62T, LB3P6T, LS1P3T, XS2P39T, XS1P32T, ZB4P13T, ZS1P14T and GT2P42T, were isolated from ice, cryoconite and meltwater of five Tibetan Plateau glaciers. All strains were Gram-stain-negative, aerobic, rod-shaped and psychrophilic, with optimal growth at 14–20 °C and pH 7.0. 16S rRNA gene sequence similarities to validly named Flavobacterium species ranged from 98.12% to 99.56%. Phylogenomic analysis of 81 concatenated core genes positioned the 23 strains (comprising the ten novel species) within a robust monophyletic clade — the ‘Cryospheric Lineage’ — together with 31 other psychrophilic type strains predominantly from glaciers, permafrost and polar regions. Average nucleotide identity (ANI) values of ≤94.4% and digital DNA–DNA hybridization (dDDH) values of ≤57.3% against closest relatives were below species thresholds (95–96% ANI, 70% dDDH). Major fatty acids were iso-C15:0 (8.1–16.8%), iso-C15:0 3-OH (3-hydroxy, 5.2–16.0%) and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c, 10.1–27.6%), with elevated branched-chain and unsaturated components typical of cold adaptation. Polyphasic taxonomic evidence supports the description of ten novel species within the genus Flavobacterium: Flavobacterium amylolyticum sp. nov. (LB2P44T=CGMCC 1.11256T=NBRC 114815T), Flavobacterium glucosi sp. nov. (LB2P6T=CGMCC 1.11263T=NBRC 114816T), Flavobacterium esculini sp. nov. (LB1P62T=CGMCC 1.11346T=NBRC 114817T), Flavobacterium labens sp. nov. (LB3P6T=CGMCC 1.11428T=NBRC 114818T), Flavobacterium pasteuri sp. nov. (LS1P3T=CGMCC 1.11474T=NBRC 114821T), Flavobacterium rhamnosi sp. nov. (XS2P39T=CGMCC 1.23204T=NBRC 115054T), Flavobacterium frigidum sp. nov. (XS1P32T=CGMCC 1.23370T=NBRC 115055T), Flavobacterium glycogeni sp. nov. (ZB4P13T=CGMCC 1.24050T=NBRC 115056T), Flavobacterium kochi sp. nov. (ZS1P14T=CGMCC 1.24093T=NBRC 114828T) and Flavobacterium cryophilum sp. nov. (GT2P42T=CGMCC 1.24821T=NBRC 114831T).