Four strains, designated as C-2, C-17T, C-39T and Ch-15, were isolated from farmed rainbow trout samples showing clinical signs during an investigation for a fish-health screening study. The pairwise 16S rRNA gene sequence analysis showed that strain C-17T shared the highest identity level of 98.1 % with the type strain of Chryseobacterium piscium LMG 23089T while strains C-2, C-39T and Ch-15 were closely related to Chryseobacterium balustinum DSM 16775T with an identity level of 99.3 %. A polyphasic approach involving phenotypic, chemotaxonomic and genome-based analyses was employed to determine the taxonomic provenance of the strains. The overall genome relatedness indices including dDDH and ANI analyses confirmed that strains C-2, C-17T, C-39T and Ch-15 formed two novel species within the genus Chryseobacterium. Chemotaxonomic analyses showed that strains C-17T and C-39T have typical characteristics of the genus Chryseobacterium by having phosphatidylethanolamine in their polar lipid profile, MK-6 as only isoprenoid quinone and the presence of iso-C15:0 as major fatty acid. The genome size and G + C content of the strains ranged between 4.4 and 5.0 Mb and 33.5 - 33.6 %, respectively. Comprehensive genome analyses revealed that the strains have antimicrobial resistance genes, prophages and horizontally acquired genes in addition to secondary metabolite-coding gene clusters. In conclusion, based on the polyphasic analyses conducted on the present study, strains C-17T and C-39T are representatives of two novel species within the genus Chryseobacterium, for which the names Chryseobacterium turcicum sp. nov. and Chryseobacterium muglaense sp. nov. with the type strains C-17T (=JCM 34190T = KCTC 82250T) and C-39T (=JCM 34191T = KCTC 822251T), respectively, are proposed.
Keywords: Antimicrobial resistance genes; Aquaculture; Chryseobacterium; Oncorhynchus mykiss; Rainbow trout.
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