scholarly journals Transcriptional Organization and Function of Invasion Genes within Salmonella enterica Serovar Typhimurium Pathogenicity Island 1, Including the prgH,prgI, prgJ, prgK, orgA,orgB, and orgC Genes

2000 ◽  
Vol 68 (6) ◽  
pp. 3368-3376 ◽  
Author(s):  
Joanna R. Klein ◽  
Thomas F. Fahlen ◽  
Bradley D. Jones
Keyword(s):  
Epithelial Cells ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Pathogenicity Island ◽  
Pcr Analysis ◽  
Intestinal Epithelial ◽  
Reading Frame ◽  
Bacterial Proteins ◽  
Serovar Typhimurium ◽  
And Function

ABSTRACT Salmonella enterica serovar Typhimurium initiates infection of a host by inducing its own uptake into specialized M cells which reside within the epithelium overlaying Peyer's patches. Entry of Salmonella into intestinal epithelial cells is dependent upon invasion genes that are clustered together inSalmonella pathogenicity island 1 (SPI-1). Upon contact between serovar Typhimurium and epithelial cells targeted for bacterial internalization, bacterial proteins are injected into the host cell through a type III secretion system that leads to internalization of the bacteria. Previous work has established that the prgH, -I, -J, and -K and orgAgenes reside in SPI-1, and the products of these genes are predicted to be components of the invasion secretion apparatus. We report that an error in the published orgA DNA sequence has been identified so that this region encodes two small genes rather than a single large open reading frame. These genes have been designatedorgA and orgB. Additionally, an opening reading frame downstream of orgB, which we have designatedorgC, has been identified and partially characterized. Previously published work has indicated that the prgH, -I, -J, and -K genes are transcribed from a promoter distinct from that used by the gene immediately downstream, orgA. Here, we present experiments indicating that orgA expression is driven by theprgH promoter. In addition, using reverse transcriptase PCR analysis, we have found that this polycistronic message extends downstream of prgH to include a total of 10 genes. To more fully characterize this invasion operon, we demonstrate that theprgH, prgI, prgJ, prgK,orgA, and orgB genes are each required for invasion and secretion, while orgC is not essential for the invasive phenotype.

scholarly journals Salmonella enterica Serovar Typhimurium Invasion Is Repressed in the Presence of Bile

2000 ◽  
Vol 68 (12) ◽  
pp. 6763-6769 ◽  
Author(s):  
A. M. Prouty ◽  
J. S. Gunn
Keyword(s):  
Epithelial Cells ◽  
Cell Invasion ◽  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Eukaryotic Cell ◽  
Intestinal Epithelial ◽  
Two Component System ◽  
Serovar Typhimurium ◽  
Invasive Capacity

ABSTRACT As enteric pathogens, the salmonellae have developed systems by which they can sense and adapt appropriately to deleterious intestinal components that include bile. Previously, growth in the presence of bile was shown to repress the transcription of prgH, a locus encoding components of the Salmonella pathogenicity island I (SPI-1) type III secretion system (TTSS) necessary for eukaryotic cell invasion. This result suggested an existing interaction between salmonellae, bile, and eukaryotic cell invasion. Transcription assays demonstrated that invasion gene regulators (e.g.,sirC and invF) are repressed by bile. However, bile does not interact with any of the invasion regulators directly but exerts its effect at or upstream of the two-component system at the apex of the invasion cascade, SirA-BarA. As suggested by the repression of invasion gene transcription in the presence of bile, Western blot analysis demonstrated that proteins secreted by the SPI-1 TTSS were markedly reduced in the presence of bile. Furthermore, Salmonella enterica serovar Typhimurium grown in the presence of bile was able to invade epithelial cells at only 4% of the level of serovar Typhimurium grown without bile. From these data, we propose a model whereby serovar Typhimurium uses bile as an environmental signal to repress its invasive capacity in the lumen of the intestine, but upon mucous layer penetration and association with intestinal epithelial cells, where the apparent bile concentration would be reduced, the system would become derepressed and invasion would be initiated.

scholarly journals Regulation of CorA Mg2+ Channel Function Affects the Virulence of Salmonella enterica Serovar Typhimurium

2008 ◽  
Vol 190 (19) ◽  
pp. 6509-6516 ◽  
Author(s):  
Krisztina M. Papp-Wallace ◽  
Michael E. Maguire
Keyword(s):  
Epithelial Cells ◽  
Metabolic Pathways ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Primary Source ◽  
Selective Inhibitor ◽  
High Concentration ◽  
Protein Levels ◽  
Serovar Typhimurium ◽  
And Function

ABSTRACT The CorA Mg2+ channel is the primary source of intracellular Mg2+ in Salmonella enterica serovar Typhimurium. In another study, we found that a strain lacking corA was attenuated in mice and also defective for invasion and replication within Caco-2 epithelial cells (K. M. Papp-Wallace, M. Nartea, D. G. Kehres, S. Porwollik, M. McClelland, S. J. Libby, F. C. Fang, and M. E. Maguire, J. Bacteriol. 190:6517-6523, 2008). Therefore, we further examined Salmonella interaction with Caco-2 epithelial cells. Inhibiting CorA acutely or chronically with a high concentration of a selective inhibitor, Co(III) hexaammine, had no effect on S. enterica serovar Typhimurium invasion of Caco-2 epithelial cells. Complementing the corA mutation with corA from various species rescued the invasion defect only if the complementing allele was functional and if it was evolutionarily similar to S. enterica serovar Typhimurium CorA. One explanation for these results could be that regulation of CorA function is needed for optimal virulence. Further experiments examining corA transcription, CorA protein content, CorA transport, and cell Mg2+ content indicated that both CorA expression and CorA function are differentially regulated. Moreover, the rates of Mg2+ influx via CorA are not closely correlated with either protein levels or Mg2+ content. We conclude that loss of the CorA protein disrupts a regulatory network(s) with the ultimate phenotype of decreased virulence. This conclusion is compatible with the microarray results in our other study, which showed that loss of corA resulted in changes in transcription (and protein expression) in multiple metabolic pathways (Papp-Wallace et al., J. Bacteriol. 190:6517-6523, 2008). Further study of the regulation of CorA expression and function provides an opportunity to dissect the complexity of Mg2+ homeostasis and its ties to virulence within the bacterium.

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