Chitinophaga oryzae sp. nov., an epiphytic bacterium isolated from rice root surfaces

Abstract

Two Gram-stain-negative, non-motile, rod-shaped bacterial strains were isolated from the surfaces of rice roots. They were designated as strains 1303T and 1310. Their colonies were circular, entire, opaque, convex and yellow. They were chitinase- and catalase-positive, reduced nitrate and grew at 16–37 °C (optimum, 30 °C), pH 5.0–10.0 (optimum, pH 7.0) and 0–2.0% NaCl (optimum, 1.0 %). Based on the 16S rRNA gene sequence analysis, they were classified as members of the genus Chitinophaga . Results of phylogenetic and phylogenomic analyses indicated that they formed a cluster with Chitinophaga eiseniae YC6729T, Chitinophaga qingshengii JN246T, Chitinophaga varians 10-7 W-9003T and Chitinophaga fulva G-6-1-13T. When the genomic sequences of strains 1303T and 1310 were compared with their close relatives, the average nucleotide identity and digital DNA–DNA hybridization values were below the cut-off levels. Phosphatidylethanolamine was the major polar lipid. MK-7 was the major respiratory quinone. iso-C15 : 0, C16 : 1  ω5c, iso-C17 : 0 3-OH and summed feature 3 (C16 : 1  ω7c/C16 : 1  ω6c) were the predominant fatty acids. Differential characteristics between both strains and their close relatives were also observed. Based on the distinctions in genotypic, phenotypic and chemotypic features, strains 1303T and 1310 represent members of a novel species of the genus Chitinophaga , for which the name Chitinophaga oryzae sp. nov. is proposed. The type strain is 1303T (=KACC 22075T=TBRC 12926T).