Isolation of Chryseobacterium siluri sp. nov., from liver of diseased catfish (Silurus asotus)

Woo Taek Oh,Sang Guen Kim,Sang Wha Kim,Jin Woo Jun,Sib Sankar Giri,Saekil Yun,Hyoun Joong Kim,Se Jin Han,Jun Kwon,Se Chang Park

doi:10.1016/j.heliyon.2020.e03454

Abstract

Yellow-pigmented, circular bacteria (strain SNU WT7) were isolated from the liver of moribund eastern catfish (Silurus asotus). Our study focused on the taxonomic description of SNU WT7 using phylogenetic, phenotypic, and chemotaxonomic analyses. The 16S rRNA gene sequence of the SNU WT7 strain was highly similar to that of Chryseobacterium haifense H38T (97.29% similarity), followed by Chryseobacterium hominis P2K6T (97.22% similarity), while other species exhibited similarity values of less than 97.0%. The genome of strain SNU WT7 displayed average nucleotide identity and genome-to-genome distance values of 72.35% and 22.0%, respectively, which clearly indicated that the novel species was distant from the other Chryseobacterium species, with its closest relative being C. haifense H38T. Furthermore, the phenotypic characteristics, including acid production from glucose, D-fructose, lactose, and maltose, of strain SNU WT 7 differed from those of C. haifense H38T. The major polar lipid of the strain was phosphatidylethanolamine, and several unidentified aminolipids and lipids were also present. Similar to other Chryseobacterium species, the quinone system was composed mainly of MK-6. The genome of SNU WT7 is 2,690,367 bp with a G + C content of 43.6%. Taken together, our data indicate that the isolate SNU WT7 represents a novel species of the genus Chryseobacterium. Thus, we present the name Chryseobacterium siluri sp. nov. for the novel type strain SNU WT7T (KCTC 72626, JCM 33707).

Highlights

The genus Chryseobacterium, which belongs to class Flavobacteriia and family Flavobacteriaceae, was first described by Vandamme et al in 1994 [1]
Our study suggested the strain to be one of the novel species among Chryseobacterium group based on the analysis result of its 16S rRNA gene sequence, phylogenetic study, whole genome sequence, and phenotypic characteristics
Strain SNU WT 7 exhibited the highest similarity to C. haifense H38T (97.29% sequence similarity), followed by C. hominis DSM 19326T (97.22%), C. pallidum DSM 18015T (96.73%), and C. molle DSM 18016T

Summary

Introduction

The genus Chryseobacterium, which belongs to class Flavobacteriia and family Flavobacteriaceae, was first described by Vandamme et al in 1994 [1]. Chryseobacterium spp. are detected in both healthy as well as diseased individuals, and despite their presence in diverse environments under normal conditions, they are considered to be pathogenic and are associated with numerous infections in both humans [5] and animals [6]. Chryseobacterium spp. are associated with numerous infections in aquatic animals, especially fish, with various species reported to be pathogenic in different kinds of fish [6, 10]. As it exhibits resistance to multiple antibiotics, Chryseobacterium is considered to be a serious bacterial pathogen that threatens aquaculture [10]. In this context, we isolated a bacterial strain belonging to the genus Chryseobacterium from a catfish (Silurus asotus) farm in Korea. Meet the criteria for classification in novel species of bacteria and our study present C. siluri as a novel bacterial species isolated from Korean catfish (Silurus asotus)

Isolation and ecology

Complete genome sequence and genome comparison

Phenotypic characterization

Results and discussion

Protologue

Competing interest statement