Polaromonas glacialis sp. nov. and Polaromonas cryoconiti sp. nov., isolated from alpine glacier cryoconite

The taxonomic positions of two Gram-staining-negative, psychrophilic bacteria, which were isolated from alpine glacier cryoconite and designated strains Cr4-12^T and Cr4-35^T, were investigated using a polyphasic approach. Both novel strains contained ubiquinone Q-8 as the sole quinone, summed feature 3 (C_16 : 1ω7c and/or C_16 : 1ω6c) and C_16 : 0 as the dominant cellular fatty acids, putrescine and 2-hydroxyputrescine as the major polyamines, and diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine as the major polar lipids. The genomic DNA G+C contents of strains Cr4-12^T and Cr4-35^T were 61.3 mol% and 60.7 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the two strains belonged to the genus Polaromonas. Although the 16S rRNA gene sequences of strains Cr4-12^T and Cr4-35^T were very similar (98.7 % sequence similarity), hybridizations indicated a DNA–DNA relatedness value of only 26.9 % between the two novel strains. In pairwise comparisons with the type strains of recognized Polaromonas species, strains Cr4-12^T and Cr4-35^T showed 16S rRNA gene sequence similarities of 96.4–98.5 % and 96.5–98.4 %, respectively. Based on the phenotypic and phylogenetic evidence and DNA–DNA relatedness data, strains Cr4-12^T and Cr4-35^T represent two novel species within the genus Polaromonas, for which the names Polaromonas glacialis sp. nov. and Polaromonas cryoconiti sp. nov., respectively, are proposed. The type strain of Polaromonas glacialis sp. nov. is Cr4-12^T ( = DSM 24062^T  = LMG 26049^T  = KACC 15089^T) and that of Polaromonas cryoconiti sp. nov. is Cr4-35^T ( = DSM 24248^T  = LMG 26050^T  = KACC 15090^T).