Chryseobacterium tagetis sp. nov., a plant growth promoting bacterium with an antimicrobial activity isolated from the roots of medicinal plant (Tagetes patula).

A novel plant growth-promoting and indole acetic acid (IAA) producing strain designated RG1T was isolated from the roots of Tagetes patula (marigold) collected from Goyang, South Korea. The cells of strain RG1T is aerobic, yellow, Gram-stain-negative, pleomorphic and non-motile. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain RG1T belongs to the genus Chryseobacterium and is closely related to Chryseobacterium gwangjuense THG-A18T (98.6%). The strain produced IAA (70.5 µg ml-1) in the presence of L-tryptophan and showed antimicrobial activity against Gram-negative bacterium Xanthomonas campestris pv. campestris KACC 10377T. The isolate had a significant positive effect on rice plant shoot and root growth. The novel strain RG1T had a draft genome size of 4,430,189 bp, with ten scaffolds and 3969 protein-coding genes. The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain RG1T and other closely related members ranged from 21.5 to 36.6% and from 79.2 to 86.6%, respectively. The genomic DNA G + C content was 34.8 mol%. Furthermore, anti-SMASH analysis of the whole genome revealed six putative biosynthetic gene clusters responsible for various secondary metabolites. The major respiratory quinone was MK-6 and the major fatty acids were iso-C15:0, summed feature 3 (comprising C16: 1ω7c and/or C16: 1ω6c) and summed feature 9 (comprising iso-C17: 1 ω9c and/or 10-methyl C16:0). The major polar lipid is phosphatidylethanolamine. Based on the genotypic, chemotaxonomic and physiological data, strain RG1T represents a novel species, for which the name Chryseobacterium tagetis sp. nov. is proposed. The type strain is designated as RG1T ( = KCTC 82696T = NBRC 115057T).