Using bacterial pan-genomes obtained through whole genome sequencing (WGS), coding DNA sequences (CDSs) can be clustered into pan-genome orthologous groups (POGs). We aimed to investigate comparative genomic features of Streptococcus canis based on POG analysis and to determine CDSs specific to prevalent sequence type (ST) 9. Twenty WGS datasets from S. canis strains, including invasive and non-invasive specimens, were retrieved from the National Center for Biotechnology Information Assembly database. Based on the WGS data, we performed comparative genome hybridization (CGH), pan- and core-genome prediction, Venn diagram testing with five ST9 strains, and phylogenetic analysis with ST determination. We compared the CDSs of seven ST9 and 13 non-ST9 strains. We observed genomic diversity based on CGH and Venn diagram analyses. The predicted pan- and core-genomes contained 4,772 and 1,403 genes, respectively. We found five clades consisting of different STs (ST1, ST44/2, ST13/14, ST21/15/41, and ST9) based on the phylogenetic tree. There were differences in four pathways (DNA restriction-modification system, DNA-mediated transposition, extracellular region, and response to oxidative stress) regulated by CDSs specific to ST9. Our findings describe genomic diversity in CGH and Venn diagram testing, pan- and core-genomes, five clades of genomes consisting of different STs, and unique CDS features associated with ST9.
Keywords: Streptococcus canis; comparative genomics; pan-genome orthologous group; sequence type; whole genome sequencing.