Isolation and characterization of two new species, Hymenobacter mellowenesis sp. nov. and Hymenobacter aranciens sp. nov., from soil

Strains M29^T and ASUV-10-1^T, which are aerobic, non-flagellated, and Gram-stain-negative, were isolated from soil samples collected in Inje (37°57’49.1"N 128°19’53.7"E) and Cheonan City (36°48’47.1"N 127°05’22.4"E), South Korea. Phylogenetic analyses based on rRNA gene sequences revealed that strains M29^T and ASUV-10-1^T form a distinct branch within the family Hymenobacter (order Cytophagales, class Cytophagia). Strain M29^T is most closely related to Hymenobacter rubidus DG7B^T with a 16 S rRNA gene sequence similarity of 97.05%. Strain ASUV-10-1^T shows closest genetic similarity to Hymenobacter frigidus B1789^T (96.42%), Hymenobacter jeongseonensis BT683^T (95.97%), and Hymenobacter terricola 3F2T^T (95.65%). The optimal growth conditions for these strains are pH 7.0, no NaCl, and a temperature of 25 °C. The dominant cellular fatty acids identified in these strains are iso-C_15:0, anteiso-C_15:0, and Summed Feature 3 (C_16:1ω 7c / C_16:1ω 6c). Both strains predominantly contain MK-7 as the respiratory quinone. The major polar lipids in strains M29^T and ASUV-10-1^T are phosphatidylethanolamine, aminophospholipid, and aminolipid. Based on biochemical, chemotaxonomic, and phylogenetic data, it is evident that M29^T and ASUV-10-1^T represent new species within the genus Hymenobacter. The new species were classified based on biochemical and chemotaxonomic characteristics. The taxonomic classification of these species was conducted following the guidelines and protocols outlined in Bergey’s Manual of Systematic Bacteriology. We followed the methods for determining physiological and biochemical characteristics, as well as chemotaxonomic markers such as fatty acid profiles, quinone types, and polar lipid compositions. We also compared with the results of carbohydrate utilization and enzyme activities results [Bergey 1994]. Therefore, we propose the names Hymenobacter mellowenesis for strain M29^T (= KCTC 102056^T = NBRC 116578^T) and Hymenobacter aranciens for strain ASUV-10-1^T (= KCTC 92969^T = NBRC 116575^T).