Evolution of Salmonella Chromosomes and Its Influence on Gene Expression and Chromosomal Conformation

Salmonella is one of the most important bacterial pathogens in the world, causing an estimated 120 million infections each year. There is considerable diversity, with ∼2,600 serovars, but it remains unclear how the genomes have evolved as the species and subspecies of Salmonella differentiate. Here, we have reconstructed the ancient orthologous chromosomes of each major Salmonella lineage and traced their evolutionary process. In total, 911 rearrangement events were identified, with 64% of events occurring in a locus-specific way. Using RNA sequencing and multi-strain association analysis, we demonstrate that genetic rearrangements have a significant effect on gene expression across Salmonella lineages. Moreover, we perform chromosome conformation capture (3C) sequencing analysis, which demonstrates large variations for the organization of ter chromosomal interaction domains among Salmonella lineages. In conclusion, our work delineates the evolutionary trajectory of Salmonella chromosomes, and demonstrates the influence of rearrangements on gene expression profiles and chromosomal conformation.