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 degrees C and pH 7.0 without NaCl. The major cellular fatty acids were identified as iso-C-15:0 and C-16:1 omega 5c. 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.