Oryzicola mucosus gen. nov., sp. nov., a novel slime producing bacterium belonging to the family Phyllobacteriaceae isolated from the rhizosphere of rice plants.

A novel Gram-stain negative, asporogenous, slimy, rod-shaped, non-motile bacterium ROOL2 was isolated from the root samples collected from a rice field located in Ilsan, South Korea. Phylogenetic analysis of the 16S rRNA sequence showed 96.5% similarity to Tianweitania sediminis Z8 followed by species of genera Mesorhizobium (96.4-95.6%), Aquabacterium (95.9-95.7%), Rhizobium (95.8%) and Ochrobactrum (95.6%). Strain ROOL2 grew optimally at 30 °C in the presence of 1-6% (w/v) NaCl and at pH 7.5. The major respiratory quinone was ubiquinone-10 and the major cellular fatty acids were Cω7c, summed feature 4 (comprising iso-C I and/or anteiso-C B) and summed feature 8 (comprising Cω6c and/or Cω7c). The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidylmethylethanolamine, phosphatidylglycerol, one unidentified aminolipid and two unidentified lipids. The assembled draft genome of strain ROOL2 had 28 contigs with N50 value of 656,326 nt, total length of 4,894,583 bp and a DNA G + C content of 61.5%. The average amino acid identity (AAI) values of strain ROOL2 against the genomes of related members belonging to the same family were below 68% and the ANI and dDDH values between the strain ROOL2 and the type strains of phylogenetically related species were 61.8-76.3% and 19.4-21.1%, respectively. Strain ROOL2 only produces carotenoid-type pigment when grown on LB agar and slime on R2A agar. In the presence of tryptophan, strain ROOL2 produced indole acetic acid (IAA), a phytohormone in plant growth and development. Gene clusters for indole-3-glycerol phosphatase and tryptophan synthase were found in the genome of strain ROOL2. The genotypic and phenotypic characteristics indicated that strain ROOL2 represents a novel genus belonging the family Phyllobacteriaceae, for which the name Oryzicola mucosus gen. nov., sp. nov. is proposed. The type strain is ROOL2 (KCTC 82711 = NBRC 114717).