scholarly journals Delineation of the Salmonella enterica Serovar Typhimurium HilA Regulon through Genome-Wide Location and Transcript Analysis

2007 ◽  
Vol 189 (13) ◽  
pp. 4587-4596 ◽  
Author(s):  
Inge M. V. Thijs ◽  
Sigrid C. J. De Keersmaecker ◽  
Abeer Fadda ◽  
Kristof Engelen ◽  
Hui Zhao ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Target Genes ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Effector Proteins ◽  
Transcript Analysis ◽  
Genome Wide ◽  
Serovar Typhimurium ◽  
Genes Encoding

ABSTRACT The Salmonella enterica serovar Typhimurium HilA protein is the key regulator for the invasion of epithelial cells. By a combination of genome-wide location and transcript analysis, the HilA-dependent regulon has been delineated. Under invasion-inducing conditions, HilA binds to most of the known target genes and a number of new target genes. The sopB, sopE, and sopA genes, encoding effector proteins secreted by the type III secretion system on Salmonella pathogenicity island 1 (SPI-1), were identified as being both bound by HilA and differentially regulated in an HilA mutant. This suggests a cooperative role for HilA and InvF in the regulation of SPI-1-secreted effectors. Also, siiA, the first gene of SPI-4, is both bound by HilA and differentially regulated in an HilA mutant, thus linking this pathogenicity island to the invasion key regulator. Finally, the interactions of HilA with the SPI-2 secretion system gene ssaH and the flagellar gene flhD imply a repressor function for HilA under invasion-inducing conditions.

scholarly journals Secretion of the orgC Gene Product by Salmonella enterica Serovar Typhimurium

2003 ◽  
Vol 71 (11) ◽  
pp. 6680-6685 ◽  
Author(s):  
James B. Day ◽  
Catherine A. Lee
Keyword(s):  
Gene Product ◽  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Virulence Genes ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Type Iii Secretion System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Serovar Typhimurium ◽  
Transposon Insertions

ABSTRACT HilA activates the transcription of genes on Salmonella pathogenicity island 1 (SPI1), which encodes a type III secretion system (TTSS). Previous studies showed that transposon insertions in orgC, a gene located on SPI1, increase hilA expression. We characterize the orgC gene product and show that it is secreted via the SPI1 TTSS. We propose a model whereby OrgC functions as a secreted repressor of the SPI1 virulence genes.

scholarly journals SiiE Is Secreted by the Salmonella enterica Serovar Typhimurium Pathogenicity Island 4-Encoded Secretion System and Contributes to Intestinal Colonization in Cattle

2007 ◽  
Vol 75 (3) ◽  
pp. 1524-1533 ◽  
Author(s):  
Eirwen Morgan ◽  
Alison J. Bowen ◽  
Sonya C. Carnell ◽  
Timothy S. Wallis ◽  
Mark P. Stevens
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Type I ◽  
Intestinal Colonization ◽  
Serovar Typhimurium

ABSTRACT Here we report that Salmonella enterica serovar Typhimurium pathogenicity island 4 carries a type I secretion system (siiCDF) which secretes an ∼600-kDa protein (encoded by siiE). SiiE is surface expressed, and its production is regulated by HilA. SiiE and SiiF influence colonization in cattle and the invasion of bovine enterocytes.

scholarly journals RamA, a Member of the AraC/XylS Family, Influences Both Virulence and Efflux in Salmonella enterica Serovar Typhimurium

2010 ◽  
Vol 192 (6) ◽  
pp. 1607-1616 ◽  
Author(s):  
Andrew M. Bailey ◽  
Al Ivens ◽  
Rob Kingsley ◽  
Jennifer L. Cottell ◽  
John Wain ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Target Genes ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Consensus Sequence ◽  
Altered Expression ◽  
Expression Of Genes ◽  
Mouse Macrophages ◽  
Serovar Typhimurium ◽  
Genes Encoding ◽  
High Level

ABSTRACT The transcriptomes of Salmonella enterica serovar Typhimurium SL1344 lacking a functional ramA or ramR or with plasmid-mediated high-level overexpression of ramA were compared to those of the wild-type parental strain. Inactivation of ramA led to increased expression of 14 SPI-1 genes and decreased expression of three SPI-2 genes, and it altered expression of ribosomal biosynthetic genes and several amino acid biosynthetic pathways. Furthermore, disruption of ramA led to decreased survival within RAW 264.7 mouse macrophages and attenuation within the BALB/c ByJ mouse model. Highly overexpressed ramA led to increased expression of genes encoding multidrug resistance (MDR) efflux pumps, including acrAB, acrEF, and tolC. Decreased expression of 34 Salmonella pathogenicity island (SPI) 1 and 2 genes, decreased SipC production, decreased adhesion to and survival within macrophages, and decreased colonization of Caenorhabditis elegans were also seen. Disruption of ramR led to the increased expression of ramA, acrAB, and tolC, but not to the same level as when ramA was overexpressed on a plasmid. Inactivation of ramR had a more limited effect on pathogenicity gene expression. In silico analysis of a suggested RamA-binding consensus sequence identified target genes, including ramR, acrA, tolC, sipABC, and ssrA. This study demonstrates that the regulation of a mechanism of MDR and expression of virulence genes show considerable overlap, and we postulate that such a mechanism is dependent on transcriptional activator concentration and promoter sensitivity. However, we have no evidence to support the hypothesis that increased MDR via RamA regulation of AcrAB-TolC gives rise to a hypervirulent strain.

scholarly journals The Salmonella Pathogenicity Island 2-Encoded Type III Secretion System Is Essential for the Survival of Salmonella enterica Serovar Typhimurium in Free-Living Amoebae

2009 ◽  
Vol 75 (6) ◽  
pp. 1793-1795 ◽  
Author(s):  
Benjamin Bleasdale ◽  
Penelope J. Lott ◽  
Aparna Jagannathan ◽  
Mark P. Stevens ◽  
Richard J. Birtles ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Type Iii Secretion System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Free Living ◽  
Type Iii ◽  
Serovar Typhimurium ◽  
Potential Reservoir

ABSTRACT Free-living amoebae represent a potential reservoir and predator of Salmonella enterica. Through the use of type III secretion system (T3SS) mutants and analysis of transcription of selected T3SS genes, we demonstrated that the Salmonella pathogenicity island 2 is highly induced during S. enterica serovar Typhimurium infection of Acanthamoeba polyphaga and is essential for survival within amoebae.

scholarly journals Genetic Analysis of Colistin Resistance in Salmonella enterica Serovar Typhimurium

2009 ◽  
Vol 53 (6) ◽  
pp. 2298-2305 ◽  
Author(s):  
Song Sun ◽  
Aurel Negrea ◽  
Mikael Rhen ◽  
Dan I. Andersson
Keyword(s):  
Mutation Rate ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Clinical Settings ◽  
Missense Mutations ◽  
Regulator Protein ◽  
Serovar Typhimurium ◽  
Sensor Kinases ◽  
Genes Encoding

ABSTRACT Colistin is a cyclic cationic peptide that kills gram-negative bacteria by interacting with and disrupting the outer membrane. We isolated 44 independent mutants in Salmonella enterica serovar Typhimurium with reduced susceptibility to colistin and identified 27 different missense mutations located in the pmrA and pmrB genes (encoding the regulator and sensor of a two-component regulatory system) that conferred increased resistance. By comparison of the two homologous sensor kinases, PmrB and EnvZ, the 22 missense mutations identified in pmrB were shown to be located in four different structural domains of the protein. All five pmrA mutations were located in the phosphate receiver domain of the regulator protein. The mutants appeared at a mutation rate of 0.6 × 10−6 per cell per generation. The MICs of colistin for the mutants increased 2- to 35-fold, and the extent of killing was reduced several orders of magnitude compared to the susceptible strain. The growth rates of the mutants were slightly reduced in both rich medium and M9-glycerol minimal medium, whereas growth in mice appeared unaffected by the pmrA and pmrB mutations. The low fitness costs and the high mutation rate suggest that mutants with reduced susceptibility to colistin could emerge in clinical settings.

Identification of Salmonella enterica Serovar Typhimurium Using Specific PCR Primers Obtained by Comparative Genomics in Salmonella Serovars

2006 ◽  
Vol 69 (7) ◽  
pp. 1653-1661 ◽  
Author(s):  
H. J. KIM ◽  
S. H. PARK ◽  
T. H. LEE ◽  
B. H. NAHM ◽  
Y. H. CHUNG ◽  
...  
Keyword(s):  
Comparative Genomics ◽  
Salmonella Enterica ◽  
Target Genes ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Foodborne Pathogen ◽  
Pcr Primers ◽  
Genomic Sequences ◽  
Local Alignment ◽  
Serovar Typhimurium ◽  
Salmonella Serovars

Salmonella enterica serovar Typhimurium is a major foodborne pathogen throughout the world. Until now, the specific target genes for the detection and identification of serovar Typhimurium have not been developed. To determine the specific probes for serovar Typhimurium, the genes of serovar Typhimurium LT2 that were expected to be unique were selected with the BLAST (Basic Local Alignment Search Tool) program within GenBank. The selected genes were compared with 11 genomic sequences of various Salmonella serovars by BLAST. Of these selected genes, 10 were expected to be specific to serovar Typhimurium and were not related to virulence factor genes of Salmonella pathogenicity island or to genes of the O and H antigens of Salmonella. Primers for the 10 selected genes were constructed, and PCRs were evaluated with various genomic DNAs of Salmonella and non-Salmonella strains for the specific identification of Salmonella serovar Typhimurium. Among all the primer sets for the 10 genes, STM4497 showed the highest degree of specificity to serovar Typhimurium. In this study, a specific primer set for Salmonella serovar Typhimurium was developed on the basis of the comparison of genomic sequences between Salmonella serovars and was validated with PCR. This method of comparative genomics to select target genes or sequences can be applied to the specific detection of microorganisms.

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