A novel Gram-stain-negative strain, designated ZYY5T, was isolated from rice roots. Results of 16S rRNA gene analysis indicated that strain ZYY5T was a member of the genus Dickeya, with a highest similarity to Dickeya zeae DSM 18068T (98.5%). The major fatty acids were summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), C16:0 and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). Multi-locus sequence analysis using five concatenated genes (16S rRNA, atpD, infB, recA and gyrB) and phylogenomic analysis based on 2940 core gene sequences showed that strain ZYY5T formed a robust cluster with strains EC1, ZJU1202, DZ2Q, NCPPB 3531 and CSL RW192, while separated from the other strains of D. zeae. The orthologous average nucleotide identity (ANI) and digital DNA-DNAhybridization (dDDH) values among these six strains ranged from 96.8-99.9% and 73.7-99.8%, which supported that they were belonged to the same species. However, strain ZYY5T shared 58.4 of dDDH and 94.5% of ANI values with type strain D. zeae DSM 18068T, which were lower than the proposed species boundary cut-off for dDDH and ANI. The genomic analysis revealed that strain ZYY5T contained virulence-associated genes, which is same as the phylogenetic-related strains of the genus Dickeya. Based on the results of the polyphasic approaches, we propose that strain ZYY5T represents a novel species in the genus Dickeya, for which the name Dickeya oryzae sp. nov. (=JCM 33020 T=ACCC 61554 T) is proposed. Strains EC1, ZJU1202, DZ2Q, NCPPB 3531 and CSL RW192 should also be classified in the same genomospecies of D. oryzae same as ZYY5T.
Keywords: Dickeya; genome; polyphasic taxonomy; rice endophytic bacteria.