Two yellow-pigmented, Gram-stain-negative and rod-shaped bacterial strains, designated as RY24T and ZYY160, were isolated from rice. Results of phylogenetic analysis based on 16S rRNA gene sequences showed that strains RY24T and ZYY160 belonged to the genus Pseudomonas, and the 16S rRNA gene sequence similarity was 100 % The DNA homology between the two strains was 99.7 %. The 16S rRNA and rpoD gene sequences of the two strains showed highest similarity values to Pseudomonas oryzihabitans CGMCC 1.3392T and Pseudomonas psychrotolerans DSM 15758T (sharing 99.31 and 94.34 %, respectively). The major fatty acids of two strains were identified as summed feature 8 (C18:1ω7c and/or C18:1ω6c), C16;0 and summed feature 3 (C16:1ω7c and/or C16:1ω6c), and the major respiratory quinone was identified as ubiquinone Q-9, which are typical chemotaxonomic features of members of the genus Pseudomonas. The genomic DNA G+C contents of strains RY24T and ZYY160 were determined to be 64.25 and 64.21 mol%, respectively. The DNA-DNA relatedness and average nucleotide identity values between the two strains and their closely related type strains were below 36 and 90 %, which supported that RY24T and ZYY160 represent a novel species in the genus Pseudomonas. Phylogenetic and chemotaxonomic evidence, together with phenotypic characteristics, showed that the two isolates constitute a novel species of the genus Pseudomonas. The type strain is RY24T (JCM 33201T=ACCC 61555T), for which the name Pseudomonas rhizoryzae sp. nov. is proposed.
Keywords: Pseudomonas; endophytic bacteria; rhizosphere; rice seeds.