title: Differences in Salmonella enterica serovar Typhimurium strain invasiveness are associated with heterogeneity in SPI-1 gene expression.
abstract: Most studies on Salmonella enterica serovar Typhimurium infection focus on strains ATCC SL1344 or NTCC 12023 (ATCC 14028). We have compared the abilities of these strains to induce membrane ruffles and invade epithelial cells. S. Typhimurium strain 12023 is less invasive and induces smaller membrane ruffles on MDCK cells compared with SL1344. Since the SPI-1 effector SopE is present in SL1344 and absent from 12023, and SL1344 sopE mutants have reduced invasiveness, we investigated whether 12023 is less invasive due to the absence of SopE. However, comparison of SopE(+) and SopE(-) S. Typhimurium strains, sopE deletion mutants and 12023 expressing a sopE plasmid revealed no consistent relationship between SopE status and relative invasiveness. Nevertheless, absence of SopE was closely correlated with reduced size of membrane ruffles. A PprgH-gfp reporter revealed that relatively few of the 12023 population (and that of the equivalent strain ATCC 14028) express SPI-1 compared to other S. Typhimurium strains. Expression of a PhilA-gfp reporter mirrored that of PprgH-gfp in 12023 and SL1344, implicating reduced signalling via the transcription factor HilA in the heterogeneous SPI-1 expression of these strains. The previously unrecognized strain heterogeneity in SPI-1 expression and invasiveness has important implications for studies of Salmonella infection.
authors.affiliation: School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Leann
authors.initials: L
authors.lastname: Clark
authors.affiliation: School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Perrett
authors.affiliation: School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Layla
authors.initials: L
authors.lastname: Malt
authors.affiliation: School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Caryn
authors.initials: C
authors.lastname: Harward
authors.affiliation: School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Humphrey
authors.affiliation: School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Katy A
authors.initials: KA
authors.lastname: Jepson
authors.affiliation: School of Cellular and Molecular Medicine, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Isabel
authors.initials: I
authors.lastname: Martinez-Argudo
authors.affiliation: School of Cellular and Molecular Medicine, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Carney
authors.affiliation: Microbial Sciences Division, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK.|Department of Bacteriology, Veterinary Laboratories Agency, Weybridge, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB, UK.
authors.forename: Roberto M
authors.initials: RM
authors.lastname: La Ragione
authors.affiliation: School of Veterinary Sciences, University of Bristol, Langford, Bristol BS40 5DU, UK.
authors.forename: Tom J
authors.initials: TJ
authors.lastname: Humphrey
authors.affiliation: School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Jepson
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000382:microbiology; D015870:Gene Expression; D017930:Genes, Reporter; D044404:Genomic Islands / Q000235:genetics*; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D017384:Sequence Deletion; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D037521:Virulence Factors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C102236:HilA protein, Salmonella; C079790:PrgH protein, Salmonella typhimurium; C103987:SopE protein, Salmonella; D015534:Trans-Activators; D037521:Virulence Factors