Genome Comparisons of Salmonella: Functional Conservation of Genes within Pathogenicity Islands (pp. 237-249)
Authors: (Alison Garner, Anish Bavishi, Cole Anderson, Madhusudan Choudhary, Aaron M. Lynne, Department of Biological Sciences, Sam Houston State University, Huntsville, Texas, USA)
Abstract: Members of Salmonella are able to infect a wide range of hosts with some subspecies and serovars being host-specific while others are wide host range organisms. Salmonella is most commonly associated with humans, food animals (bovine, swine and poultry) and reptiles such as turtles, lizards, and iguanas. The exact nature of this diversity towards host susceptibility is still unclear. In the present study, whole genomes and subsequent protein homologues from Salmonella Pathogenicity Islands 1 and 2 of several Salmonella serovars were analyzed for their structure-function constraints to identify evolutionary pressures. Whole genome alignment showed no explicit pattern of rearrangement, phylogenetic trees of pathogenicity islands genes revealed that the branch lengths were very small, and functional constraint analysis revealed that most of these genes were operating under negative selection. The results indicate that genes of Salmonella Pathogenicity Island 1 and 2 are functionally conserved across serovars, regardless of host range. Thus, the present result suggests that genes located in the pathogenic islands may not be sufficient solely for host specificity and pathogenesis, and other accessory proteins from different strains as well as host factors may play an important role in influencing the severity of the outcome of the diseases.