Rhodocytophaga rosea sp. nov. and Nibribacter ruber sp. nov., two radiation-resistant bacteria isolated from soil

Two bacterial strains, 172606-1^T and BT10^T, were isolated from soil, Korea. Both strains were Gram-stain-negative and rod-shaped bacteria. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain 172606-1^T formed a distinct lineage within the family Cytophagaceae (order Cytophagales, class Cytophagia, phylum Bacteroidetes). Strain 172606-1^T was most closely related to a member of the genus Rhodocytophaga (93.8% 16S rRNA gene sequence similarity to Rhodocytophaga aerolata 5416T-29^T). The complete genome sequence of strain 172606-1^T is 8,983,451 bp size. Optimal growth occurred at 25 °C and pH 7.0 without NaCl. The major cellular fatty acids were identified as iso-C_15:0 and C_16:1 ω5c. The major respiratory quinone was MK-7. The major polar lipid was phosphatidylethanolamine. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain BT10^T belongs to the genus Nibribacter and is closely related to Nibribacter koreensis GSR 3061^T (96.5%), Rufibacter glacialis MDT1-10-3^T (95.7%), Rufibacter sediminis H-1^T (95.1%) and Rufibacter quisquiliarum CAI-18b^T (94.9%). The complete genome sequence of strain BT10^T is 4,374,810 bp size. The predominant (> 10%) cellular fatty acids of strain BT10^T were iso-C_15:0 and summed feature 4 (anteiso-C_17:1 B/iso-C_17:1 I) and a predominant quinone was MK-7. In addition, strain BT10^T has phosphatidylethanolamine (PE) as the major polar lipid. On the basis of biochemical, chemotaxonomic and phylogenetic analyses, strain 172606-1^T represents a novel bacterial species of the genus Rhodocytophaga, for which the name Rhodocytophaga rosea is proposed and strain BT10^T represents a novel species of the genus Nibribacter, for which the name Nibribacter ruber is proposed. The type strains of Rhodocytophaga rosea and Nibribacter ruber are 172606-1^T (= KCTC 62096^T = NBRC 114410^T) and BT10^T (= KCTC 62607^T = NBRC 114383^T), respectively.