Complete Genome Analysis of A Virulent Vibrio Scophthalmi Strain VSc190401 Isolated form Diseased Marine Fish Half-Smooth Tongue Sole, Cynoglossus Semilaevis

Abstract

Background: Vibrio scophthalmi is an opportunistic bacterial pathogen, which is widely distributed in marine environment. Earlier studies have suggested that it is a normal microorganism in 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 mechanism.Results: In 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 3,185 coding genes. Among these genes, 2,648, 2,298 and 1,915 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 database 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.Conclusions: Based 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 might be complicated.