Salmonella gallinarum: Distinct genomic insertions/deletions and rare rearrangements

Salmonella gallinarum is a fowl-adapted pathogen, causing typhoid-like fever in chickens. It has the same antigenic formula as Salmonella pullorum, which is also adapted to fowl but causes pullorum disease. The close relatedness but distinct pathogenesis make this pair of fowl pathogens good models for the studies of bacterial genomic evolution and the way they acquired their pathogenicity. To locate and characterize the genomic differences between S. gallinarum and other Salmonella, we constructed a genome map of S. gallinarum SARB21. On the genome map, we located two regions with increased lengths (insertions) and six regions with decreased lengths (deletions) relative to S. typhimurium LT2. With bioinformatics tools, we identified the deleted regions as prophages, and genes for effector proteins, fimbriae, and a type I restriction system in S. typhimurium LT2. In addition, we analyzed the genomic structures of wild type strains of S. gallinarum and S. pullorum, and found that genomic rearrangements were widespread in these bacteria.