Complete genome sequence of Salmonella enterica serovar typhimurium LT2

Salmonella enterica subspecies I, serovar Typhimurium (S. typhimurium), is a leading cause of human gastroenteritis, and is used as a mouse model of h uman typhoid fever(1). The incidence of non-typhoid salmonellosis is increa sing worldwide(2-4), causing millions of infections and many deaths in the human population each year. Here we sequenced the 4,857-kilobase (kb) chrom osome and 94-kb virulence plasmid of S. typhimurium strain LT2. The distrib ution of close homologues of S. typhimurium LT2 genes in eight related ente robacteria was determined using previously completed genomes of three relat ed bacteria, sample sequencing of both S. enterica serovar Paratyphi A (S. paratyphi A) and Klebsiella pneumoniae, and hybridization of three unsequen ced genomes to a microarray of S. typhimurium LT2 genes. Lateral transfer o f genes is frequent, with 11% of the S. typhimurium LT2 genes missing from S. enterica serovar Typhi (S. typhi), and 29% missing from Escherichia coli K12. The 352 gene homologues of S. typhimurium LT2 confined to subspecies I of S. enterica- containing most mammalian and bird pathogens(5)- are usef ul for studies of epidemiology, host specificity and pathogenesis. Most of these homologues were previously unknown, and 50 may be exported to the per iplasm or outer membrane, rendering them accessible as therapeutic or vacci ne targets.