Removal of the phage-shock protein PspB causes reduction of virulence in Salmonella enterica serovar Typhimurium independently of NRAMP1

The phage-shock protein (Psp) system is believed to manage membrane stress in all Enterobacteriaceae and has recently emerged as being important for virulence in several pathogenic species of this phylum. The core of the Psp system consists of the pspA–D operon and the distantly located pspG gene. In Salmonella enterica serovar Typhimurium (S. Typhimurium), it has recently been reported that PspA is essential for systemic infection of mice, but only in NRAMP1+ mice, signifying that attenuation is related to coping with divalent cation starvation in the intracellular environment. In the present study, we investigated the contribution of individual psp genes to virulence of S. Typhimurium. Interestingly, deletion of the whole pspA–D set of genes caused attenuation in both NRAMP1+ and NRAMP1− mice, indicating that one or more of the psp genes contribute to virulence independently of NRAMP1 expression in the host. Investigations of single gene mutants showed that knock out of pspB reduced virulence in both types of mice, while deletion of pspA only caused attenuation in NRAMP1+ mice, and deletion of pspD had a minor effect in NRAMP1− mice, while deletions of either pspC or pspG did not affect virulence. Experiments addressed at elucidating the role of PspB in virulence revealed that PspB is dispensable for uptake to and intracellular replication in cultured macrophages and resistance to complement-induced killing. Furthermore, the Psp system of S. Typhimurium was dispensable during pIV-induced secretin stress. In conclusion, our results demonstrate that removal of PspB reduces virulence in S. Typhimurium independently of host NRAMP1 expression, demonstrating that PspB has roles in intra-host survival distinct from the reported contributions of PspA.

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Role of Periplasmic Peptidylprolyl Isomerases in Salmonella enterica Serovar Typhimurium Virulence

Infection and Immunity ◽

10.1128/iai.71.9.5386-5388.2003 ◽

2003 ◽

Vol 71 (9) ◽

pp. 5386-5388 ◽

Cited By ~ 27

Author(s):

Sue Humphreys ◽

Gary Rowley ◽

Andrew Stevenson ◽

William J. Kenyon ◽

Michael P. Spector ◽

...

Keyword(s):

Sigma Factor ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Minor Effect ◽

Alternative Sigma Factor ◽

Macrophage Cell ◽

Serovar Typhimurium ◽

A Minor ◽

Peptidylprolyl Isomerase

ABSTRACT FkpA is a peptidylprolyl isomerase whose expression is regulated by the alternative sigma factor, sigma factor E (σE). In contrast to the results of a previous report, inactivation of fkpA was found to have only a minor effect on the ability of Salmonella enterica serovar Typhimurium to invade and survive within epithelial and macrophage cell lines and cause infection in mice. However, an effect of the fkpA mutation on serovar Typhimurium virulence was seen if the mutation was combined with mutations in surA or htrA, two other σE-regulated genes, which encode proteins involved in protein folding and/or degradation in the periplasm.

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Cystathionine β-Lyase Is Important for Virulence of Salmonella enterica Serovar Typhimurium

Infection and Immunity ◽

10.1128/iai.72.6.3310-3314.2004 ◽

2004 ◽

Vol 72 (6) ◽

pp. 3310-3314 ◽

Cited By ~ 43

Author(s):

Linda J. Ejim ◽

Vanessa M. D'Costa ◽

Nadine H. Elowe ◽

J. Concepción Loredo-Osti ◽

Danielle Malo ◽

...

Keyword(s):

Salmonella Enterica ◽

Biosynthetic Pathway ◽

Antibacterial Agents ◽

Antimicrobial Agents ◽

Salmonella Enterica Serovar Typhimurium ◽

Systemic Infection ◽

Bacterial Virulence ◽

Methionine Biosynthesis ◽

Insertional Inactivation ◽

Serovar Typhimurium

ABSTRACT The biosynthesis of methionine in bacteria requires the mobilization of sulfur from Cys by the formation and degradation of cystathionine. Cystathionine β-lyase, encoded by metC in bacteria and STR3 in Schizosaccharomyces pombe, catalyzes the breakdown of cystathionine to homocysteine, the penultimate step in methionine biosynthesis. This enzyme has been suggested to be the target for pyridinamine antimicrobial agents. We have demonstrated, by using purified enzymes from bacteria and yeast, that cystathionine β-lyase is not the likely target of these agents. Nonetheless, an insertional inactivation of metC in Salmonella enterica serovar Typhimurium resulted in the attenuation of virulence in a mouse model of systemic infection. This result confirms a previous chemical validation of the Met biosynthetic pathway as a target for the development of antibacterial agents and demonstrates that cystathionine β-lyase is important for bacterial virulence.

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Role of Toll-Like Receptor 4 in Macrophage Activation and Tolerance during Salmonella enterica Serovar Typhimurium Infection

Infection and Immunity ◽

10.1128/iai.71.9.4873-4882.2003 ◽

2003 ◽

Vol 71 (9) ◽

pp. 4873-4882 ◽

Cited By ~ 34

Author(s):

Qian Li ◽

Bobby J. Cherayil

Keyword(s):

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Peritoneal Macrophages ◽

Phagocytic Cells ◽

Necrosis Factor Alpha ◽

Tnf Α ◽

Serovar Typhimurium ◽

Tlr4 Gene ◽

Factor Alpha

ABSTRACT Toll-like receptors (TLRs) play an important role in the innate immune response, particularly in the initial interaction between the infecting microorganism and phagocytic cells, such as macrophages. We investigated the role of TLR4 during infection of primary murine peritoneal macrophages with Salmonella enterica serovar Typhimurium. We found that macrophages from the C3H/HeJ mouse strain, which carries a functionally inactive Tlr4 gene, exhibit marked impairment of tumor necrosis factor alpha (TNF-α) secretion in response to S. enterica serovar Typhimurium infection. However, activation of extracellular growth factor-regulated kinase and NF-κB signaling pathways was relatively unaffected, as was increased expression of TNF-α mRNA. Furthermore, macrophage tolerance, which is associated with increased expression of the NF-κB p50 and p52 subunits, was induced by S. enterica serovar Typhimurium even in the absence of functional TLR4. These results indicate that during infection of macrophages by S. enterica serovar Typhimurium, TLR4 signals are required at a posttranscriptional step to maximize secretion of TNF-α. Signals delivered by pattern recognition receptors other than TLR4 are sufficient for the increased expression of the TNF-α transcript and at least some genes associated with macrophage tolerance.

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Virulence Plasmid-Borne spvB and spvC Genes Can Replace the 90-Kilobase Plasmid in Conferring Virulence to Salmonella enterica Serovar Typhimurium in Subcutaneously Inoculated Mice

Journal of Bacteriology ◽

10.1128/jb.183.15.4652-4658.2001 ◽

2001 ◽

Vol 183 (15) ◽

pp. 4652-4658 ◽

Cited By ~ 69

Author(s):

Hidenori Matsui ◽

Christopher M. Bacot ◽

Wendy A. Garlington ◽

Thomas J. Doyle ◽

Steve Roberts ◽

...

Keyword(s):

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Systemic Infection ◽

Reticuloendothelial System ◽

Host Cells ◽

Virulence Plasmid ◽

Replication Rate ◽

Oral Inoculation ◽

Low Copy Number ◽

Serovar Typhimurium

ABSTRACT In a mouse model of systemic infection, the spv genes carried on the Salmonella enterica serovar Typhimurium virulence plasmid increase the replication rate of salmonellae in host cells of the reticuloendothelial system, most likely within macrophages. A nonpolar deletion in the spvB gene greatly decreased virulence but could not be complemented by spvBalone. However, a low-copy-number plasmid expressing spvBCfrom a constitutive lacUV5 promoter did complement thespvB deletion. By examining a series of spvmutations and cloned spv sequences, we deduced thatspvB and spvC could be sufficient to confer plasmid-mediated virulence to S. enterica serovar Typhimurium. The spvBC-bearing plasmid was capable of replacing all of the spv genes, as well as the entire virulence plasmid, of serovar Typhimurium for causing systemic infection in BALB/c mice after subcutaneous, but not oral, inoculation. A point mutation in the spvBC plasmid preventing translation but not transcription of spvC eliminated the ability of the plasmid to confer virulence. Therefore, it appears that both spvB and spvC encode the principal effector factors for Spv- and plasmid-mediated virulence of serovar Typhimurium.

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SoxS regulates the expression of the Salmonella enterica serovar Typhimurium ompW gene

Microbiology ◽

10.1099/mic.0.027433-0 ◽

2009 ◽

Vol 155 (8) ◽

pp. 2490-2497 ◽

Cited By ~ 15

Author(s):

F. Gil ◽

I. Hernández-Lucas ◽

R. Polanco ◽

N. Pacheco ◽

B. Collao ◽

...

Keyword(s):

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Regulatory Region ◽

Transcription Start ◽

Mobility Shift ◽

Serovar Typhimurium ◽

A Minor ◽

Electrophoretic Mobility Shift Assays ◽

Putative Binding Site ◽

Transcriptional Fusions

OmpW of Salmonella enterica serovar Typhimurium has been described as a minor porin involved in osmoregulation, and is also affected by environmental conditions. Biochemical and genetic evidence from our laboratory indicates that OmpW is involved in efflux of and resistance towards paraquat (PQ), and its expression has been shown to be activated in response to oxidative stress. In this study we have explored ompW expression in response to PQ. Primer extension and transcriptional fusions showed that its expression was induced in the presence of PQ. In silico analyses suggested a putative binding site for the SoxS transcriptional factor at the ompW regulatory region. Electrophoretic mobility shift assays (EMSAs) and footprinting experiments showed that SoxS binds at a region that starts close to −54 and ends at about −197 upstream of the transcription start site. Transcriptional fusions support the relevance of this region in ompW activation. The SoxS site is in the forward orientation and its location suggests that the ompW gene has a class I SoxS-dependent promoter.

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Flagella and Chemotaxis Are Required for Efficient Induction of Salmonella enterica Serovar Typhimurium Colitis in Streptomycin-Pretreated Mice

Infection and Immunity ◽

10.1128/iai.72.7.4138-4150.2004 ◽

2004 ◽

Vol 72 (7) ◽

pp. 4138-4150 ◽

Cited By ~ 210

Author(s):

Bärbel Stecher ◽

Siegfried Hapfelmeier ◽

Catherine Müller ◽

Marcus Kremer ◽

Thomas Stallmach ◽

...

Keyword(s):

Virulence Factors ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Innate Immune ◽

Gastrointestinal Infections ◽

Infection Models ◽

Serovar Typhimurium ◽

Efficient Induction ◽

Toll Like Receptor 5

ABSTRACT Salmonella enterica subspecies 1 serovar Typhimurium is a common cause of gastrointestinal infections. The host's innate immune system and a complex set of Salmonella virulence factors are thought to contribute to enteric disease. The serovar Typhimurium virulence factors have been studied extensively by using tissue culture assays, and bovine infection models have been used to verify the role of these factors in enterocolitis. Streptomycin-pretreated mice provide an alternative animal model to study enteric salmonellosis. In this model, the Salmonella pathogenicity island 1 type III secretion system has a key virulence function. Nothing is known about the role of other virulence factors. We investigated the role of flagella in murine serovar Typhimurium colitis. A nonflagellated serovar Typhimurium mutant (fliGHI) efficiently colonized the intestine but caused little colitis during the early phase of infection (10 and 24 h postinfection). In competition assays with differentially labeled strains, the fliGHI mutant had a reduced capacity to get near the intestinal epithelium, as determined by fluorescence microscopy. A flagellated but nonchemotactic cheY mutant had the same virulence defects as the fliGHI mutant for causing colitis. In competitive infections, both mutants colonized the intestine of streptomycin-pretreated mice by day 1 postinfection but were outcompeted by the wild-type strain by day 3 postinfection. Together, these data demonstrate that flagella are required for efficient colonization and induction of colitis in streptomycin-pretreated mice. This effect is mostly attributable to chemotaxis. Recognition of flagellar subunits (i.e., flagellin) by innate immune receptors (i.e., Toll-like receptor 5) may be less important.

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Role of the alternative sigma factors σ E and σ S in survival of Salmonella enterica serovar Typhimurium during starvation, refrigeration and osmotic shock

Microbiology ◽

10.1099/mic.0.29235-0 ◽

2007 ◽

Vol 153 (1) ◽

pp. 263-269 ◽

Cited By ~ 39

Author(s):

Alisdair McMeechan ◽

Mark Roberts ◽

Tristan A. Cogan ◽

Frieda Jørgensen ◽

Andrew Stevenson ◽

...

Keyword(s):

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Osmotic Shock ◽

Sigma Factors ◽

Alternative Sigma Factors ◽

Serovar Typhimurium

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The enzyme phosphoglucomutase (Pgm) is required by Salmonella enterica serovar Typhimurium for O-antigen production, resistance to antimicrobial peptides and in vivo fitness

Microbiology ◽

10.1099/mic.0.029553-0 ◽

2009 ◽

Vol 155 (10) ◽

pp. 3403-3410 ◽

Cited By ~ 22

Author(s):

G. K. Paterson ◽

D. B. Cone ◽

S. E. Peters ◽

D. J. Maskell

Keyword(s):

Antimicrobial Peptides ◽

Salmonella Enterica ◽

Salmonella Enterica Serovar Typhimurium ◽

Live Attenuated Vaccine ◽

Antigen Production ◽

O Antigen ◽

Serovar Typhimurium

The enzyme phosphoglucomutase (Pgm) catalyses the interconversion of glucose 1-phosphate and glucose 6-phosphate and contributes to glycolysis and the generation of sugar nucleotides for biosynthesis. To assess the role of this enzyme in the biology of the pathogen Salmonella enterica serovar Typhimurium we have characterized a pgm deletion mutant in strain SL1344. Compared to SL1344, SL1344 pgm had impaired growth in vitro, was deficient in the ability to utilize galactose as a carbon source and displayed reduced O-antigen polymer length. The mutant was also more susceptible to antimicrobial peptides and showed decreased fitness in the mouse typhoid model. The in vivo phenotype of SL1344 pgm indicated a role for pgm in the early stages of infection, most likely through deficient O-antigen production. Although pgm mutants in other pathogens have potential as live attenuated vaccine strains, SL1344 pgm was not sufficiently attenuated for such use.

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