Strain CA7T, a Gram-stain-negative, non-motile, non-spore-forming, aerobic and rod-shaped bacterial strain, was isolated from raw cow's milk collected from a farm affiliated with Chung-Ang University, Anseong, Korea, and characterized by a polyphasic approach. Optimal growth of strain CA7T was observed on tryptic soy agar at 30 °C and pH 7.0 with 0 % NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain CA7T belonged to the genus Chryseobacterium. The most closely related strains (16S rRNA gene sequence similarity indicated in parentheses), based on the phylogenetic analysis, were Chryseobacterium rhizosphaerae KCTC 22548T (98.08 %), Chryseobacterium nakagawai CCUG 60563T (98.61 %), Chryseobacterium jejuense KACC 12501T (97.85 %) and Chryseobacterium aurantiacum KCTC 62135T (97.78 %). Whole genome sequencing indicated that the genome size was 5 125 723 bp and had a DNA G+C content of 37.4 mol%. Average nucleotide identity values for strain CA7T with C. rhizosphaerae, C. nakagawai, C. jejuense, C. aurantiacum, and the type species of the genus Chryseobacterium, C. gleum, were 80.2, 79.8, 79.8, 79.6 and 80.4 %, respectively. The digital DNA-DNA hybridization values of CA7T compared to C. rhizosphaerae, C. nakagawai, C. jejuense, C. aurantiacum and C. gleum were 24.1, 23.9, 23.9, 23.7 and 24.3 %, respectively. The major fatty acids were iso-C15 : 0, summed feature 9 (iso-C17 : 1 ω9c and/or C16 : 0 10-methyl), iso-C17 : 0 3-OH and summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1 ω7c). Menaquinone-6 was the only respiratory quinone. The major polar lipid was phosphatidylethanolamine. Based on this polyphasic taxonomic study, strain CA7T represents a novel species of the genus Chryseobacterium for which the name Chryseobacterium vaccae sp. nov. is proposed. The type strain is CA7T (=KACC 21402T=JCM 33749T).
Keywords: Chryseobacterium strain CA7T; Chryseobacterium vaccae; bovine raw milk.