In the present study, in an attempt to explore the diversity of bacteria in the roots of rice plants, a Gram-stain-negative, motile, facultatively anaerobic, non-pigmented, catalase-positive, oxidase-negative and rod-shaped bacterium with polar flagella was isolated. Phylogenetic analysis based on 16S rRNA gene sequences revealed highest sequence similarity to Limnohabitans parvus KCTC 42859T (98.2%) followed by Limnohabitans curvus KCTC 42562T (98%), Limnohabitans planktonicicus II-D5T (97.9%) and Limnohabitans australis MWH-BRAZ-DAM2DT (97.4%). Growth of strain JUR4T occurred at 10-37 °C (optimum, 30 °C), at pH 5.5-8.0 (optimum, 6.5-7) and in the presence of 0-0.2% NaCl (optimum, 0%, w/v). The genome size of strain JUR4T was found to be 3.34 Mb containing 3139 predicted protein-coding genes with a DNA G+C content of 61.5 mol%. The digital DNA-DNA hybridization and average nucleotide identity values between the genome sequence of strain JUR4T and closely related reference strains were 21.0-24.8% and 74.7-81.4%, respectively. Strain JUR4T contained diphosphatidylglycerol, phoshatidylethanolamine, one unidentified phosphoglycolipid, one unidentified aminophosphoglycolipid, one unidentified phospholipid and seven unidentified glycolipids. The major fatty acids were C16:0 and summed feature 3 (comprising C16:1 ω7c and/or C16:1 ω6c), and ubiquinone Q-8 was the sole isoprenoid quinone. So far, all species belonging to the genus Limnohabitans have been described as non-motile and devoid of flagella. All species were isolated from freshwater and are therefore denoted as planktonic bacteria. This present study introduces a novel motile member of Limnohabitans isolated from the root of rice plant, and introduces the genes associated with motility and methyl-accepting chemotaxis proteins. Phylogenetic, phenotypic, chemotaxonomic and genotypic data clearly indicates that strain JUR4T represents a novel species of the genus Limnohabitans for which the name Limnohabitans radicicola sp. nov. is proposed. The type strain is JUR4T (=KACC 21745T=NBRC 114484T).
Keywords: Limnohabitans radicicola; non-pigmented; polar flagella; rhizosphere.