PCR-based genotyping of carrier strains for 18 genes absolutely unique to D30 and in-silico comparison with other genomes. Panel A represents the bovine pathogenicity island present in D30 and 930918-3 as compared to the complete BPI described. Polymorphism in BPI is common and it is apparent in the two strains. Panel B details the transposon that carries the putative T7SS in D30. Many genes of this transposon are absent in 930918-3. Panel C in the figure shows the presence (black) or absence (white) of the 18 genes that constitute the Unique Non-Fragmented (UNF) gene group in D30. The genes are divided based on the mobile element of origin. It can be seen majority of these genes are borne on a transposable element. Also the bovine pathogenicity element (SaPIBov) contributes to four genes in three reading frames where genes BPI13 and BPI14 are fused. It is interesting to note the placement of strains USA300 and NCTC8325 in this figure. USA300 is similar to D30 (14 of 18 genes present) while NCTC8325 has a profile very similar to 930918-3. This placement is in contrast with their overall proximity to each other (Figures 1 and 3B). Such disparity between overall proximity and carriage status stresses the importance of mobile genetic elements in nasal carriage.