scholarly journals In Vivo Genetic Analysis Indicates That PhoP-PhoQ and the Salmonella Pathogenicity Island 2 Type III Secretion System Contribute Independently to Salmonella enterica Serovar Typhimurium Virulence

2001 ◽  
Vol 69 (12) ◽  
pp. 7254-7261 ◽  
Author(s):  
Carmen R. Beuzón ◽  
Kate E. Unsworth ◽  
David W. Holden
Keyword(s):  
Virulence Factors ◽  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Type Iii Secretion System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Type Iii ◽  
Serovar Typhimurium

ABSTRACT Many virulence factors are required for Salmonella enterica serovar Typhimurium to replicate intracellularly and proliferate systemically within mice. In this work, we have carried out genetic analyses in vivo to determine the functional relationship between two major virulence factors necessary for systemic infection byS. enterica serovar Typhimurium: theSalmonella pathogenicity island 2 (SPI-2) type III secretion system (TTSS) and the PhoP-PhoQ two-component regulatory system. Although previous work suggested that PhoP-PhoQ regulates SPI-2 TTSS gene expression in vitro, in vivo competitive analysis of mutant strains indicates that these systems contribute independently toS. typhimurium virulence. Our results also suggest that mutation of phoP may compensate partially for defects in the SPI-2 TTSS by deregulating SPI-1 TTSS expression. These results provide an explanation for previous reports showing an apparent functional overlap between these two systems in vitro.

scholarly journals Accelerated Type III Secretion System 2-Dependent Enteropathogenesis by a Salmonella enterica Serovar Enteritidis PT4/6 Strain

2009 ◽  
Vol 77 (9) ◽  
pp. 3569-3577 ◽  
Author(s):  
Mrutyunjay Suar ◽  
Balamurugan Periaswamy ◽  
Pascal Songhet ◽  
Benjamin Misselwitz ◽  
Andreas Müller ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Alternative Pathway ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Mucosal Inflammation ◽  
Classical Pathway ◽  
Type Iii ◽  
Serovar Typhimurium

ABSTRACT Salmonella enterica subsp. I serovars Typhimurium and Enteritidis are major causes of enteric disease. The pathomechanism of enteric infection by serovar Typhimurium has been studied in detail. Serovar Typhimurium employs two pathways in parallel for triggering disease, i.e., the “classical” pathway, triggered by type III secretion system 1 (TTSS-1), and the “alternative” pathway, mediated by TTSS-2. It had remained unclear whether these two pathways would also explain the enteropathogenesis of strains from other serovars. We chose the isolate P125109 of the epidemic serovar Enteritidis PT4/6, generated isogenic mutants, and studied their virulence. Using in vitro and in vivo infection experiments, a dendritic cell depletion strategy, and MyD88−/− knockout mice, we found that P125109 employs both the “classical” and “alternative” pathways for triggering mucosal inflammation. The “classical” pathway was phenotypically similar in serovar Typhimurium strain SL1344 and in P125109. However, the kinetics of the “alternative” pathway differed significantly. Via TTSS-2, P125109 colonized the gut tissue more efficiently and triggered mucosal inflammation approximately 1 day faster than SL1344 did. In conclusion, our data demonstrate that different Salmonella spp. can differ in their capacity to trigger mucosal inflammation via the “alternative” pathway in vivo.

scholarly journals Functional Characterization of SsaE, a Novel Chaperone Protein of the Type III Secretion System Encoded by Salmonella Pathogenicity Island 2

2009 ◽  
Vol 191 (22) ◽  
pp. 6843-6854 ◽  
Author(s):  
Tsuyoshi Miki ◽  
Yoshio Shibagaki ◽  
Hirofumi Danbara ◽  
Nobuhiko Okada
Keyword(s):  
Protein Interactions ◽  
Type Iii Secretion ◽  
Functional Characterization ◽  
Coiled Coil ◽  
Type Iii Secretion System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Type Iii ◽  
Serovar Typhimurium

ABSTRACT The type III secretion system (T3SS) encoded by Salmonella pathogenicity island 2 (SPI-2) is involved in systemic infection and intracellular replication of Salmonella enterica serovar Typhimurium. In this study, we investigated the function of SsaE, a small cytoplasmic protein encoded within the SPI-2 locus, which shows structural similarity to the T3SS class V chaperones. An S. enterica serovar Typhimurium ssaE mutant failed to secrete SPI-2 translocator SseB and SPI-2-dependent effector PipB proteins. Coimmunoprecipitation and mass spectrometry analyses using an SsaE-FLAG fusion protein indicated that SsaE interacts with SseB and a putative T3SS-associated ATPase, SsaN. A series of deleted and point-mutated SsaE-FLAG fusion proteins revealed that the C-terminal coiled-coil domain of SsaE is critical for protein-protein interactions. Although SseA was reported to be a chaperone for SseB and to be required for its secretion and stability in the bacterial cytoplasm, an sseA deletion mutant was able to secrete the SseB in vitro when plasmid-derived SseB was overexpressed. In contrast, ssaE mutant strains could not transport SseB extracellularly under the same assay conditions. In addition, an ssaE(I55G) point-mutated strain that expresses the SsaE derivative lacking the ability to form a C-terminal coiled-coil structure showed attenuated virulence comparable to that of an SPI-2 T3SS null mutant, suggesting that the coiled-coil interaction of SsaE is absolutely essential for the functional SPI-2 T3SS and for Salmonella virulence. Based on these findings, we propose that SsaE recognizes translocator SseB and controls its secretion via SPI-2 type III secretion machinery.

scholarly journals Killing of Candida albicans Filaments by Salmonella enterica Serovar Typhimurium Is Mediated by sopB Effectors, Parts of a Type III Secretion System

2011 ◽  
Vol 10 (6) ◽  
pp. 782-790 ◽  
Author(s):  
Younghoon Kim ◽  
Eleftherios Mylonakis
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Critical Role ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Content Type ◽  
Type Iii ◽  
Serovar Typhimurium ◽  
Fungal Interactions

ABSTRACTAlthough bacterial-fungal interactions shape microbial virulence during polymicrobial infections, only a limited number of studies have evaluated this interaction on a genetic level. We report here that one interaction is mediated bysopB, an effector of a type III secretion system (TTSS) ofSalmonella entericaserovar Typhimurium. In these studies, we screened 10 TTSS effector-related mutants and determined their role in the killing ofC. albicansfilamentsin vitroduring coinfection in planktonic environments. We found that deleting thesopBgene (which encodes inositol phosphatase) was associated with a significant decrease inC. albicanskilling at 25°C after 5 days, similar to that caused by the deletion ofsipB(which encodes TTSS translocation machinery components). ThesopBdeletion dramatically influenced the killing ofC. albicansfilaments. It was associated with repressed filamentation in theCaenorhabditis elegansmodel ofC. albicans-S.Typhimurium coinfection, as well as with biofilm formation byC. albicans. We confirmed that SopB translocated to fungal filaments through SipB during coinfection. Using quantitative real-time PCR assays, we found that theCandidasupernatant upregulated theS.Typhimurium genes associated withC. albicanskilling (sopBandsipB). Interestingly, the sopBeffector negatively regulated the transcription ofCDC42, which is involved in fungal viability. Taken together, these results indicate that specific TTSS effectors, including SopB, play a critical role in bacterial-fungal interactions and are important toS.Typhimurium in order to selectively compete with fungal pathogens. These findings highlight a new role for TTSS ofS.Typhimurium in the intestinal tract and may further explain the evolution and maintenance of these traits.

scholarly journals Thioredoxin 1 Participates in the Activity of the Salmonella enterica Serovar Typhimurium Pathogenicity Island 2 Type III Secretion System

2009 ◽  
Vol 191 (22) ◽  
pp. 6918-6927 ◽  
Author(s):  
Aurel Negrea ◽  
Eva Bjur ◽  
Speranta Puiac ◽  
Sofia Eriksson Ygberg ◽  
Fredrik Åslund ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Functional Integration ◽  
Type Iii Secretion System ◽  
Pathogenicity Island ◽  
Secretion System ◽  
Type Iii ◽  
Serovar Typhimurium ◽  
Thioredoxin 1

ABSTRACT The facultative intracellular pathogen Salmonella enterica serovar Typhimurium relies on its Salmonella pathogenicity island 2 (SPI2) type III secretion system (T3SS) for intracellular replication and virulence. We report that the oxidoreductase thioredoxin 1 (TrxA) and SPI2 are coinduced for expression under in vitro conditions that mimic an intravacuolar environment, that TrxA is needed for proper SPI2 activity under these conditions, and that TrxA is indispensable for SPI2 activity in both phagocytic and epithelial cells. Infection experiments in mice demonstrated that SPI2 strongly contributed to virulence in a TrxA-proficient background whereas SPI2 did not affect virulence in a trxA mutant. Complementation analyses using wild-type trxA or a genetically engineered trxA coding for noncatalytic TrxA showed that the catalytic activity of TrxA is essential for SPI2 activity in phagocytic cells whereas a noncatalytic variant of TrxA partially sustained SPI2 activity in epithelial cells and virulence in mice. These results show that TrxA is needed for the intracellular induction of SPI2 and provide new insights into the functional integration between catalytic and noncatalytic activities of TrxA and a bacterial T3SS in different settings of intracellular infections.

scholarly journals Type III Secretion of Salmonella enterica Serovar Typhimurium Translocated Effectors and SseFG

2002 ◽  
Vol 70 (3) ◽  
pp. 1403-1409 ◽  
Author(s):  
Imke Hansen-Wester ◽  
Bärbel Stecher ◽  
Michael Hensel
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Type Iii ◽  
Serovar Typhimurium ◽  
Substrate Proteins

ABSTRACT The type III secretion system (TTSS) encoded by Salmonella enterica serovar Typhimurium pathogenicity island 2 (SPI2) is employed by Salmonella enterica for interaction with host cells during the intracellular phase of pathogenesis. This TTSS secretes a set of SPI2-encoded proteins in vitro and translocates Salmonella serovar Typhimurium translocated effectors (STE) that are encoded by genes outside of SPI2 into host cells. Using an epitope-tagging approach, we analyzed secretion of proteins by the TTSS of SPI2 and identified SseF and SseG as further secreted substrate proteins. Three members of the STE family, SifA, SifB, and SseJ, were secreted under conditions that also induce secretion of SPI2-encoded substrate proteins.

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 A Salmonella Virulence Factor Activates the NOD1/NOD2 Signaling Pathway

mBio ◽  
2011 ◽  
Vol 2 (6) ◽  
Author(s):  
A. Marijke Keestra ◽  
Maria G. Winter ◽  
Daisy Klein-Douwel ◽  
Mariana N. Xavier ◽  
Sebastian E. Winter ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Intestinal Inflammation ◽  
Inflammatory Responses ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Content Type ◽  
Type Iii

ABSTRACTThe invasion-associated type III secretion system (T3SS-1) ofSalmonella entericaserotype Typhimurium (S. Typhimurium) activates the transcription factor NF-κB in tissue culture cells and induces inflammatory responses in animal models through unknown mechanisms. Here we show that bacterial delivery or ectopic expression of SipA, a T3SS-1-translocated protein, led to the activation of the NOD1/NOD2 signaling pathway and consequent RIP2-mediated induction of NF-κB-dependent inflammatory responses. SipA-mediated activation of NOD1/NOD2 signaling was independent of bacterial invasionin vitrobut required an intact T3SS-1. In the mouse colitis model, SipA triggered mucosal inflammation in wild-type mice but not in NOD1/NOD2-deficient mice. These findings implicate SipA-driven activation of the NOD1/NOD2 signaling pathway as a mechanism by which the T3SS-1 induces inflammatory responsesin vitroandin vivo.IMPORTANCESalmonella entericaserotype Typhimurium (S. Typhimurium) deploys a type III secretion system (T3SS-1) to induce intestinal inflammation and benefits from the ensuing host response, which enhances growth of the pathogen in the intestinal lumen. However, the mechanisms by which the T3SS-1 triggers inflammatory responses have not been resolved. Here we show that the T3SS-1 effector protein SipA induces NF-κB activation and intestinal inflammation by activating the NOD1/NOD2 signaling pathway. These data suggest that the T3SS-1 escalates innate responses through a SipA-mediated activation of pattern recognition receptors in the host cell cytosol.

Sign in / Sign up

Export Citation Format

Share Document