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

Abstract

Two bacterial strains, 172606-1T and BT10T, 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 172606-1T formed a distinct lineage within the family Cytophagaceae (order Cytophagales, class Cytophagia, phylum Bacteroidetes). Strain 172606-1T was most closely related to a member of the genus Rhodocytophaga (93.8% 16S rRNA gene sequence similarity to Rhodocytophaga aerolata 5416T-29T). The complete genome sequence of strain 172606-1T is 8,983,451bp size. Optimal growth occurred at 25°C and pH 7.0 without NaCl. The major cellular fatty acids were identified as iso-C15:0 and C16:1 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 BT10T belongs to the genus Nibribacter and is closely related to Nibribacter koreensis GSR 3061T (96.5%), Rufibacter glacialis MDT1-10-3T (95.7%), Rufibacter sediminis H-1T (95.1%) and Rufibacter quisquiliarum CAI-18bT (94.9%). The complete genome sequence of strain BT10T is 4,374,810bp size. The predominant (> 10%) cellular fatty acids of strain BT10T were iso-C15:0 and summed feature 4 (anteiso-C17:1 B/iso-C17:1 I) and a predominant quinone was MK-7. In addition, strain BT10T has phosphatidylethanolamine (PE) as the major polar lipid. On the basis of biochemical, chemotaxonomic and phylogenetic analyses, strain 172606-1T represents a novel bacterial species of the genus Rhodocytophaga, for which the name Rhodocytophaga rosea is proposed and strain BT10T 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 172606-1T (= KCTC 62096T = NBRC 114410T) and BT10T (= KCTC 62607T = NBRC 114383T), respectively.