PMC:1069006 / 16036-18451 JSONTXT

{"project":"2_test","denotations":[{"id":"15781495-11677609-76989459","span":{"begin":624,"end":625},"obj":"11677609"},{"id":"15781495-11677608-76989460","span":{"begin":626,"end":628},"obj":"11677608"},{"id":"15781495-12775700-76989461","span":{"begin":629,"end":631},"obj":"12775700"},{"id":"15781495-12775700-76989462","span":{"begin":1028,"end":1030},"obj":"12775700"},{"id":"15781495-11677608-76989463","span":{"begin":1979,"end":1981},"obj":"11677608"},{"id":"15781495-11677609-76989464","span":{"begin":2406,"end":2407},"obj":"11677609"},{"id":"15781495-11677608-76989464","span":{"begin":2406,"end":2407},"obj":"11677608"},{"id":"15781495-12644504-76989464","span":{"begin":2406,"end":2407},"obj":"12644504"},{"id":"15781495-12775700-76989465","span":{"begin":2411,"end":2413},"obj":"12775700"}],"text":"Pathogenicity islands\nGenomic islands are regions of DNA on the chromosome of bacteria acquired via horizontal gene transfer. They are named pathogenicity, metabolic or resistance islands depending on functions of the genes on the islands. Salmonella have acquired a large number of virulence genes required during various stages of pathogenesis. In S.Choleraesuis, we have identified the five Salmonella pathogenicity islands (SPIs) shared by S.Typhimurium and S.Typhi. The average G+C content of the five SPIs in S.Choleraesuis genome is 46.62% (range, 43.55–50.33%). Of the five, we found variations in SPI-1, -3 and -5 (9,10,31). SPI-3 of S.Typhimurium harbors 10 genes, including the mgtCB operon that is required for survival in macrophages and growth in low-Mg2+ environment. Two genes, sugR and rhuM, were not found in SPI-3 of S.Choleraesuis. In addition, the high level of variability of sequence adjacent to selC among different Salmonella serovars implied that SPI-3 may be still evolving through gene acquisitions (31). SPI-1 and SPI-5 encode the most important invasion and enteropathology phenotypes of Salmonella. A 321 bp orf (SC1043) was found between pipB and pipC of SPI-5 in S.Choleraesuis, instead of the 431 bp orf (STM1089) in S.Typhimurium. Two genes (STM1092 and STM1093) between sopB and pipD of SPI-5 were absent in S.Choleraesuis. Within SPI-1 of S.Choleraesuis, while avrA and three other genes of unknown function (STM2901-STM2903) were not identified, three other unique genes (SC2841-SC2843) were present between pphB and STM2908. Two genes within SPI-1 of S.Typhimurium encoding a putative permease and a LysR transcriptional regulator are pseudogenes in S.Choleraesuis. The variation in SPI-1 and -5 may be another reason to explain why S.Choleraesuis produces fewer diarrheas when infecting humans. In addition to the SPIs 1-5, we also found SPI-6 and -9 (Figure 1A) that were previously identified in S.Typhi in the genome of S.Choleraesuis (10). We further discovered two SPIs (designated SPI-11 and -12) that had not been described previously and two metabolic islands in S.Choleraesuis (Table 5). These DNA segments have abnormal G+C contents that deviate from the genome average and are in proximity to tRNA genes or mobile elements. All the major SPIs, including SPIs 1-5 and the newly described SPIs 11-12 are highly conserved among the three Salmonella genomes (9–11,31)."}