Comparison of Salmonella genomes
Ye Feng, Wei-Qiao Liu, Kenneth E. Sanderson, and Shu-Lin Liu
from: Salmonella: From Genome to Function (Edited by: Steffen Porwollik). Caister Academic Press, U.K. (2011)
Salmonella contains over 2600 known lineages, each with distinct biological characteristics, including differences in the niche in which they dwell and the nature of diseases they may cause in their hosts. Genomic sequence analysis is beginning to reveal the genetic basis that determines the phenotypic differences among them. Comparison of eight sequenced genomes of Salmonella subgroup I lineages, which infect warm-blooded animals including humans, demonstrates that these pathogens share about 90% of their genes (the "core" genome), with the remaining ca. 10% genes being unique to each of the lineages (the "accessory" genome). Prophages and Salmonella Pathogenicity Islands (SPIs) are the main components of the accessory genome. Insertion of large DNA segments, such as SPI7 in S. Typhi, may disrupt physical balance of the genome between replication origin and terminus and rearrangements of the genome, such as inversions or translocations mediated by homologous sites (rrn operons, prophages, IS200, etc.) may accelerate rebalancing of the genome. Laterally transferred genes are the main driving force in Salmonella evolution and speciation; evidence exists indicating that mismatch repair genes may spontaneously regulate bacterial mutability through allele conversion to facilitate or inhibit incorporation of foreign DNA. Further studies may help elucidate the genetic basis of distinct pathogeneses and host ranges among the Salmonella pathogens read more ...