Abstract
A novel Gram-stain negative, asporogenous, slimy, rod-shaped, non-motile bacterium ROOL2T 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 Z8T followed by species of genera Mesorhizobium (96.4-95.6%), Aquabacterium (95.9-95.7%), Rhizobium (95.8%) and Ochrobactrum (95.6%). Strain ROOL2T 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 C18:1ω7c, summed feature 4 (comprising iso-C17:1 I and/or anteiso-C17:1 B) and summed feature 8 (comprising C18:1ω6c and/or C18:1ω7c). The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidylmethylethanolamine, phosphatidylglycerol, one unidentified aminolipid and two unidentified lipids. The assembled draft genome of strain ROOL2T had 28 contigs with N50 value of 656,326 nt, total length of 4,894,583bp and a DNA G + C content of 61.5%. The average amino acid identity (AAI) values of strain ROOL2T against the genomes of related members belonging to the same family were below 68% and the ANI and dDDH values between the strain ROOL2T and the type strains of phylogenetically related species were 61.8-76.3% and 19.4-21.1%, respectively. Strain ROOL2T only produces carotenoid-type pigment when grown on LB agar and slime on R2A agar. In the presence of tryptophan, strain ROOL2T 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 ROOL2T. The genotypic and phenotypic characteristics indicated that strain ROOL2T represents a novel genus belonging the family Phyllobacteriaceae, for which the name Oryzicola mucosusgen. nov., sp. nov. is proposed. The type strain is ROOL2T (KCTC 82711T = NBRC 114717T).
Highlights
The family Phyllobacteriaceae belongs to the order Rhizobiales, class Alphaproteobacteria and phylum Proteobacteria and was originally described by Knosel (1984)
Over 80% of rhizosphere bacteria may be capable of synthesizing indole acetic acid (IAA) The present study aimed to determine the exact taxonomic position of slime and IAA producing strain ROOL2T using a polyphasic approach, which included phenotypic, chemotaxonomic, phylogenetic and genomic analysis and results indicate that this strain represents a novel species belonging to a novel genus within the family Phyllobacteriaceae
M. tamadayense DSM 28320T and M. mediterraneum USDA 3392T were very far from strain ROOL2T and formed a different cluster in the present study, we considered T. sediminis Z8T and A. soli NK8T as reference strains for comparative analysis
Summary
The family Phyllobacteriaceae belongs to the order Rhizobiales, class Alphaproteobacteria and phylum Proteobacteria and was originally described by Knosel (1984). At the time of writing, the family consisted of twenty genera (https://lpsn.dsmz.de/family/phyllobacteriaceae). Of these Aquamicrobium species use nitrate as an alternative terminal electron acceptor, while Mesorhizobium species are facultatively chemolithotrophic and use thiosulfate or elemental sulfur as the sole energy source. The bacterial cells belonging to the family Phyllobacteriaceae are usually Gram-stain negative, rodshaped, aerobic, non-spore forming and non-motile or motile by means of polar or subpolar or lateral flagella. Over 80% of rhizosphere bacteria may be capable of synthesizing IAA The present study aimed to determine the exact taxonomic position of slime and IAA producing strain ROOL2T using a polyphasic approach, which included phenotypic, chemotaxonomic, phylogenetic and genomic analysis and results indicate that this strain represents a novel species belonging to a novel genus within the family Phyllobacteriaceae
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