In Bordetella, bpl genes are involved in the synthesis of the LPS, which has been shown to be essential for the expression of complete virulence in mice [44]. Given that the additional 14 genes unique to the S. canis genome were

absent in the other pyogenic genomes, it is possible that these loci were gained via LGT. The two genes homologous to the virulence factors discussed above, were contiguous in the genome Sepantronium suggesting they were gained in a single evolutionary event. Integrative plasmid With the exception of two loci, S. canis shared a contiguous section of 53 CDS with S. agalactiae (NEM316) (Figure 2) (see also Additional file 2: locus tags SCAZ3_04485 through SCAZ3_04760 [50,114 bp]). Sequence identity between the shared 53 CDS was very high: 99.2%. First described in S. agalactiae (NEM316) [45], this section of DNA (designated

pNEM316-1) ICG-001 datasheet was proposed to be a putative integrative plasmid (it could exist in circular form and was present as three copies within the genome). Here we designate the S. canis copy of the putative plasmid as FSL Z3-227-p. The last 24 bp at the terminal ends of pNEM316-1 were imperfect repeats of themselves (see Additional file 4). Alignment of pNEM316-1 with FSL Z3-227-p revealed identical terminal sequence for FSL Z3-227-p. Putative recombination attL and attR sites were also identified. As for pNEM316-1, these sites were 9 bp direct repeats. Figure 2 Gene organization within putative integrative plasmids for S. agalactiae strain NEM316 (plasmid designated pNEM316-1) and S. canis strain FSL Z3-227 (plasmid designated Fossariinae FSL Z3-227-p). Locus IDs for (i) CDS with putative plasmid functional role (blue arrows), and (ii) CDS homologous with established virulence factors (red arrows) are shown for S. canis (see text for detailed description). Grey arrow shows a miscellaneous feature that is a common BLAST hit with the M protein from S. pyogenes. Two horizontal black/grey bars are a generalized representation of the aligned nucleotide sequences, with black shading representing 100% identity. Figure created using Geneious

v5.1.2 and Adobe Illustrator. Annotation of several S. canis CDS within this 50 kb region suggest a plasmid functional role (Figure 2 and Additional file 2). For example, DNA topoisomerase (SCAZ3_04630), conjugation protein (SCAZ3_04680, SCAZ3_04720), and plasmid partition protein (SCAZ3_04740) were identified. In addition, four CDS were homologous with established virulence factors (see Additional file 2, locus tags are highlighted in red in the annotations worksheet). Specifically, SCAZ3_04635 (ATP-dependent clp protease) was homologous with clpE, an ATP-dependent protease from Listeria monocytogenes; clp genes have been shown to play a role in competence, development, and stress survival (thermotolerance) in S. pneumoniae[46].