Abstract
BackgroundVibrio scophthalmi is an opportunistic bacterial pathogen, which is widely distributed in the marine environment. Earlier studies have suggested that it is a normal microorganism in the turbot gut. However, recent studies have confirmed that this bacterial strain can cause diseases in many different marine animals. Therefore, it is necessary to investigate its whole genome for better understanding its physiological and pathogenic mechanisms.ResultsIn the present study, we obtained a pathogenic strain of V. scophthalmi from diseased half-smooth tongue sole (Cynoglossus semilaevis) and sequenced its whole genome. Its genome contained two circular chromosomes and two plasmids with a total size of 3,541,838 bp, which harbored 3185 coding genes. Among these genes, 2648, 2298, and 1915 genes could be found through annotation information in COG, Blast2GO, and KEGG databases, respectively. Moreover, 10 genomic islands were predicted to exist in the chromosome I through IslandViewer online system. Comparison analysis in VFDB and PHI databases showed that this strain had 334 potential virulence-related genes and 518 pathogen-host interaction-related genes. Although it contained genes related to four secretion systems of T1SS, T2SS, T4SS, and T6SS, there was only one complete T2SS secretion system. Based on CARD database blast results, 180 drug resistance genes belonging to 27 antibiotic resistance categories were found in the whole genome of such strain. However, there were many differences between the phenotype and genotype of drug resistance.ConclusionsBased on the whole genome analysis, the pathogenic V. scophthalmi strain contained many types of genes related to pathogenicity and drug resistance. Moreover, it showed inconsistency between phenotype and genotype on drug resistance. These results suggested that the physiological mechanism seemed to be complex.
Highlights
Vibrio scophthalmi is an opportunistic bacterial pathogen, which is widely distributed in the marine environment
2298 genes were annotated into three classifications in the Blast2GO database, accounting for 72.15% of total genes
The analysis results based on the Virulence Factors of Pathogenic Bacteria (VFDB) database showed that the strain VSc190401 contained 334 potential virulence genes, including four secretion systems of T1SS, T2SS, T4SS, T6SS related genes, and many different reported virulence genes
Summary
Vibrio scophthalmi is an opportunistic bacterial pathogen, which is widely distributed in the marine environment. In terms of phylogenetic status, this bacterium shares very high gene sequence similarity and amino acid identity with Vibrio ichthyoenteri [2] They have similar physiological and biochemical characteristics [3]. Earlier studies have suggested that V. scophthalmi is a type of common organism colonized in the turbot (Scophthalmus maximus) gut, which is not pathogenic and has certain host specificity for turbot [4]. This bacterium is successively isolated from diseased Paralichthys olivaceus [5], Paralichthys dentatus [6], Dentex dentex [7], Ruditapes philippinarum [8] and Thunnus maccoyii [9], supporting its pathogenicity to aquatic animals
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