Paraconexibacter antarcticus sp. nov., a novel actinobacterium isolated from Antarctic tundra soil

A Gram-negative, non-motile, aerobic bacterium, named 02-257^T, was isolated from Antarctic soil. The cells are surrounded by relatively thin capsules and were catalase-positive and oxidase-negative cocci. Growth of strain 02-257^T was observed at 4-35 °C (optimum, 28-30 °C), pH 6.0-8.0 (optimum, pH 6.0) and with 0-1.5% NaCl (optimum, 0 %). Strain 02-257 showed the highest 16S rRNA gene sequence similarity to Paraconexibacter algicola Seoho-28^T (95.06 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 02-257^T is a member of a novel species belonging to the clade formed by members of the genus Paraconexibacter in the family Paraconexibacteraceae. The DNA G+C content was 72.9 mol%. Strain 02-257^T contained C_16 : 0-iso (23.0 %), C_{18  :  1} ω9c (13.8 %), C_16 : 0 (12.5 %) and C_17 : 1 ω9c-iso (10.8 %) as major cellular fatty acids and menaquinone MK-7(H₄) was detected as the only isoprenoid quinone. Diphosphatidylglycerol, phosphatidylinositol, phosphatidylinositole mannoside, phosphatidylinositole dimannoside, unidentified phosphoglycolipid, unidentified aminophospholipid, two unidentified phospholipids, three unidentified aminolipids and six unidentified lipids were the major polar lipids. meso-Diaminopimelic acids were the diagnostic diamino acids in the cell-wall peptidoglycan. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain 02-257^T is considered to represent a novel species of the genus Paraconexibacter, for which the name Paraconexibacter antarcticus sp. nov. is proposed. The type strain is 02-257^T (=CCTCC AB 2021030^T=KCTC 49619^T).