Chryseobacterium cucumeris sp nov., an endophyte isolated from cucumber (Cucumis sativus L.) root, and emended description of Chryseobacterium arthrosphaerae

Abstract

The Gram-stain-negative, yellow-pigmented, rod-shaped bacterial strain GSE06(T), isolated from the surface-sterilized root of a cucumber plant grown in a field in Gunsan, Korea, was characterized by not only cultural and morphological features but also physiological, biochemical and molecular analyses. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain GSE06(T) was most closely related to species of the genus Chryseobacterium. Furthermore, strain GSE06(T) exhibited the highest sequence similarities with the type strains Chryseobacterium indologenes ATCC 29897(T) (98.9 %), Chryseobacterium gleum ATCC 35910(T) (98.8 %), Chryseobacterium arthrosphaerae CC-VM-7(T) (98.7 %), Chryseobacterium contaminans C26(T) (98.5 %), Chryseobacterium artocarpi UTM-3(T) (98.3 %), and Chryseobacterium gallinarum 100(T) (97.9 %). Average nucleotide identity values between genome sequences of strain GSE06(T) and the above-mentioned reference strains ranged from 81.2 to 86.9 %, which were lower than the threshold of 95% (corresponding to a DNA-DNA reassociation value of 70 %). The DNA G+C content of strain GSE06(T) was 36.1 mol%; the predominant respiratory quinone of the strain was MK-6. The major fatty acids were iso-C-15 : 0, summed feature 9 (iso-C-17 (:) (1)omega 9c), summed feature 3 (C-16 : 1 omega 7c and/or C-16 (:) (1)omega 6c) and iso-C-17 (: 0) 3-OH. The major polar lipids were phosphatidylethanolamine, three aminolipids, one aminophospholipid, four glycolipids and one unidentified lipid. These results of phenotypic and genotypic characteristics could differentiate strain GSE06(T) from closely related type strains belonging to the genus Chryseobacterium. Thus, strain GSE06(T) is proposed as a representative of a novel species in the genus Chryseobacterium, Chryseobacterium cucumeris sp. nov. The type strain is GSE06(T) (=KACC 18798(T) =JCM 31422(T)).