The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Josep Casadesús - One of the best experts on this subject based on the ideXlab platform.
-
Virulence Plasmid interchange between strains ATCC 14028, LT2, and SL1344 of Salmonella enterica serovar Typhimurium
Plasmid, 2010Co-Authors: Meritxell García-quintanilla, Josep CasadesúsAbstract:Strains ATCC 14028 and SL1344 of Salmonella enterica serovar Typhimurium are more virulent than LT2 in the BALB/c mouse model. Virulence Plasmid swapping between strains ATCC 14208, LT2, and SL1344 does not alter their competitive indexes during mouse infection, indicating that the three Plasmids are functionally equivalent, and that their contribution to Virulence is independent from the host background. Strains ATCC 14028 and LT2 are more efficient than SL1344 as conjugal donors of the Virulence Plasmid. Virulence Plasmid swapping indicates that reduced ability of conjugal transfer is a property of the SL1344 Plasmid, not of the host strain. An A→V amino acid substitution in the TraG protein appears to be the major cause that reduces conjugal transfer in the Virulence Plasmid of SL1344. Additional sequence differences in the tra operon are found between the SL1344 Plasmid and the ATCC 14028 and LT2 Plasmids. Divergence in the tra operon may reflect the occurrence of genetic drift either after laboratory domestication or in the environment. The latter might provide evidence that possession of conjugal transfer functions is a neutral trait in Salmonella populations, a view consistent with the abundance of Salmonella isolates whose Virulence Plasmids are non-conjugative.
-
Conjugal transfer of the Salmonella enterica Virulence Plasmid in the mouse intestine.
Journal of bacteriology, 2008Co-Authors: Meritxell García-quintanilla, Francisco Ramos-morales, Josep CasadesúsAbstract:BALB/c mice were infected with two Salmonella enterica serovar Typhimurium strains, one of which lacked the Virulence Plasmid. Transconjugants were found at high frequencies in the mouse feces and at low frequencies in the liver and the spleen, suggesting that mating occurred in the gut. Laboratory conditions that mimic those of the small intestine (microaerophilic growth in the presence of 0.3 M NaCl) increased the frequency of Virulence Plasmid transfer. Sodium deoxycholate, which is found at high concentrations in the duodenum, and sodium propionate, which is abundant in the large intestine, reduced the conjugation frequency. Feces inhibited conjugation. Altogether, these observations suggested that transfer of the Virulence Plasmid occurred in the distal portion of the small intestine. Conjugation trials in ileal loops provided direct evidence that conjugal transfer of the Salmonella Virulence Plasmid occurs in the ileum in mice.
-
Bile-Induced Curing of the Virulence Plasmid in Salmonella enterica Serovar Typhimurium
Journal of bacteriology, 2006Co-Authors: Meritxell García-quintanilla, Francisco Ramos-morales, Ana I. Prieto, Laurent Barnes, Josep CasadesúsAbstract:Exposure to bile induces curing of the Virulence Plasmid in Salmonella enterica serovar Typhimurium (pSLT). Disruption of the ccdB gene increases pSLT curing, both spontaneous and induced by bile, suggesting that the pSLT ccdAB genes may encode a homolog of the CcdAB addiction module previously described in the F sex factor. Unlike the F sex factor, synthesis of pSLT-encoded pili does not confer bile sensitivity. These observations may provide insights into the evolution of Virulence Plasmids in Salmonella subspecies I, as well as the causes of Virulence Plasmid loss in other Salmonella subspecies.
-
Regulation of traJ transcription in the Salmonella Virulence Plasmid by strand‐specific DNA adenine hemimethylation
Molecular microbiology, 2005Co-Authors: Eva María Camacho, Josep CasadesúsAbstract:The traJ gene of the Virulence Plasmid of Salmonella enterica serovar Typhimurium (pSLT) encodes a transcriptional activator of the transfer operon. The leucine-responsive regulatory protein (Lrp) is an activator of traJ transcription. The upstream-activating-sequence of the pSLT traJ promoter contains two Lrp binding sites (LRP-1 and LRP-2), both necessary for transcriptional activation. The promoter-proximal site (LRP-2) contains a GATC site (GATC-II) whose methylation state affects Lrp binding: GATC-II methylation in both DNA strands decreases the affinity of Lrp for the LRP-2 site, while efficient Lrp binding occurs to a non-methylated GATC-II site. The effect of GATC-II hemimethylation on Lrp binding is strand-specific: methylation of the traJ non-coding strand permits formation of the major Lrp-DNA retardation complex, but methylation of the coding strand does not. This asymmetry supports a model in which passage of the replication fork may permit Lrp-mediated activation of conjugal transfer in one daughter Plasmid molecule but not in the other. A remarkable trait of this regulatory design is that hemimethylation of a single GATC site can generate distinct epigenetic signals in otherwise identical Plasmid DNA molecules.
Helen Wang - One of the best experts on this subject based on the ideXlab platform.
-
spatiotemporal variations in growth rate and Virulence Plasmid copy number during yersinia pseudotuberculosis infection
Infection and Immunity, 2021Co-Authors: Stephan Schneiders, Tifaine Hechard, Tomas Edgren, Kemal Avican, Maria Fällman, Anna Fahlgren, Helen WangAbstract:ABSTRACT Pathogenic Yersinia spp. depend on the activity of a potent Virulence Plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Yersinia pseudotuberculosis upregulates the Virulence Plasmid copy number (PCN) during infection and that the resulting elevated gene dose of Plasmid-encoded T3SS genes is essential for Virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the Virulence Plasmid during infection is unknown. In the present study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis Virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyer’s patches and cecum during the clonal invasive phase of the infection, while the highest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the Plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues and will be readily applicable to other infection models.
-
Spatiotemporal Variations in Growth Rate and Virulence Plasmid Copy Number during Yersinia pseudotuberculosis Infection.
Infection and immunity, 2021Co-Authors: Stephan Schneiders, Tifaine Hechard, Tomas Edgren, Kemal Avican, Maria Fällman, Anna Fahlgren, Helen WangAbstract:Pathogenic Yersinia spp. depend on the activity of a potent Virulence Plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Y. pseudotuberculosis up-regulates the Virulence Plasmid copy number (PCN) during infection and the resulting elevated gene dose of Plasmid-encoded T3SS genes is essential for Virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the Virulence Plasmid during infection is unknown. In the current study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis Virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyer's Patches and caecum during the clonal invasive phase of the infection, while the fastest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the Plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues, and will be readily applicable to other infection models.
-
Spatiotemporal Variations in Growth Rate and Virulence Plasmid Copy Number during Yersinia pseudotuberculosis Infection
2020Co-Authors: Stephan Schneiders, Tifaine Hechard, Tomas Edgren, Kemal Avican, Maria Fällman, Anna Fahlgren, Helen WangAbstract:Pathogenic Yersinia spp. depend on the activity of a potent Virulence Plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Y. pseudotuberculosis up-regulates the Virulence Plasmid copy number (PCN) during infection and the resulting elevated gene dose of Plasmid-encoded T3SS genes is essential for Virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the Virulence Plasmid during infection is unknown. In the current study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis Virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyers Patches and caecum during the clonal invasive phase of the infection, while the fastest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the Plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues, and will be readily applicable to other infection models. ImportanceStudying pathogenic bacteria proliferating inside infected hosts is challenging using traditional methods, especially the transit and reversible genetic events. The bacteria are effectively diluted by the overwhelming number of host cells present in infected tissues. Using an innovative droplet digital PCR (ddPCR) approach, we have determined the Virulence Plasmid copy number (PCN) variations and growth rates of Yersinia during the course of infection in a mouse model. Here, we show that both the Virulence Plasmid copy number and bacterial growth rates display spatiotemporal variations in mice during infection. We demonstrate that the peak-to-trough ratio can be used as a proxy for determining the growth rate of invasive bacterial pathogen during infection, and ddPCR as the method of choice for quantifying DNA in host-pathogen interaction context. This proof-of-concept ddPCR approach can be easily applied for any bacterial pathogens and any infection models, for analysis of PCN, growth dynamics and bacterial loads.
Anthony T. Maurelli - One of the best experts on this subject based on the ideXlab platform.
-
Establishment of unipolar localization of IcsA in Shigella flexneri 2a is not dependent on Virulence Plasmid determinants.
Infection and immunity, 1999Co-Authors: Robin C. Sandlin, Anthony T. MaurelliAbstract:Unipolar localization of IcsA on the surface of Shigella flexneri is required for efficient formation of actin tails and protrusions in infected eucaryotic cells. Lipopolysaccharide (LPS) mutations have been demonstrated to affect either the establishment or the maintenance of IcsA in a unipolar location, although the mechanism is unknown. In order to analyze the contribution of Virulence Plasmid determinants on the unipolar localization of IcsA, we examined the localization of IcsA expressed from a cloned Plasmid copy in two different genetic backgrounds. The localization of IcsA was first examined in a Virulence Plasmid-cured derivative of the wild-type S. flexneri 2a isolate 2457T. This approach examined the contribution of Virulence Plasmid-borne factors, including the previously identified Virulence Plasmid-borne protease that is responsible for cleaving IcsA in the outer membrane and releasing the 95-kDa secreted form from the cell surface. IcsA localization in a related but nonpathogenic Escherichia coli strain expressing LPS of the O8 serotype was also examined. IcsA surface presentation in both of these genetic backgrounds continued to be unipolar, demonstrating that Virulence Plasmid-borne determinants are not responsible for unipolar localization of IcsA. The unipolar localization of IcsA in the E. coli background suggests that a common pathway that allows IcsA to be spatially restricted to one pole on the bacterial cell surface exists in Shigella and E. coli.
-
Virulence Plasmid instability in Shigella flexneri 2a is induced by Virulence gene expression.
Infection and immunity, 1997Co-Authors: Raymond Schuch, Anthony T. MaurelliAbstract:Expression of the predominantly Plasmid-encoded Virulence regulon of Shigella flexneri 2a is induced by growth at 37 degrees C and repressed by growth at 30 degrees C. During growth at 37 degrees C, spontaneous S. flexneri mutants arise which have undergone Virulence Plasmid curing or rearrangement and no longer display the virulent phenotype. In the laboratory, the unstable nature of the Virulence Plasmid causes complete loss of Virulence in a growing population. We have undertaken an analysis of Virulence Plasmid instability, classifying events which produced individual avirulent derivatives within a virulent population and identifying the factor(s) which controlled conversion. Multiplex PCR analysis of DNA obtained from spontaneous avirulent derivatives indicated that virF and virB were deleted or otherwise inactivated in over 97% of the isolates. The virF and virB loci encode regulatory proteins required for transcriptional activation of the Virulence regulon. Inactivation of these key regulatory loci in the vast majority of avirulent derivatives which arose during growth at 37 degrees C suggested that Virulence gene expression induced Virulence Plasmid instability. Consistent with this hypothesis, we observed stable Virulence Plasmid maintenance during growth of a wild-type strain at 30 degrees C where Virulence gene expression was repressed. The Virulence Plasmid was also stably maintained in virF and virB mutants grown at 37 degrees C. Conversely, Virulence Plasmid destabilization was induced at 30 degrees C and accelerated at 37 degrees C through expression of VirF or VirB from multicopy Plasmids. These results indicate that exposure of S. flexneri to conditions favoring induction of the virulent phenotype also favor its loss. The significance of this paradox of Shigella pathogenicity is discussed.
Eva María Camacho - One of the best experts on this subject based on the ideXlab platform.
-
Regulation of traJ transcription in the Salmonella Virulence Plasmid by strand‐specific DNA adenine hemimethylation
Molecular microbiology, 2005Co-Authors: Eva María Camacho, Josep CasadesúsAbstract:The traJ gene of the Virulence Plasmid of Salmonella enterica serovar Typhimurium (pSLT) encodes a transcriptional activator of the transfer operon. The leucine-responsive regulatory protein (Lrp) is an activator of traJ transcription. The upstream-activating-sequence of the pSLT traJ promoter contains two Lrp binding sites (LRP-1 and LRP-2), both necessary for transcriptional activation. The promoter-proximal site (LRP-2) contains a GATC site (GATC-II) whose methylation state affects Lrp binding: GATC-II methylation in both DNA strands decreases the affinity of Lrp for the LRP-2 site, while efficient Lrp binding occurs to a non-methylated GATC-II site. The effect of GATC-II hemimethylation on Lrp binding is strand-specific: methylation of the traJ non-coding strand permits formation of the major Lrp-DNA retardation complex, but methylation of the coding strand does not. This asymmetry supports a model in which passage of the replication fork may permit Lrp-mediated activation of conjugal transfer in one daughter Plasmid molecule but not in the other. A remarkable trait of this regulatory design is that hemimethylation of a single GATC site can generate distinct epigenetic signals in otherwise identical Plasmid DNA molecules.
Stephan Schneiders - One of the best experts on this subject based on the ideXlab platform.
-
spatiotemporal variations in growth rate and Virulence Plasmid copy number during yersinia pseudotuberculosis infection
Infection and Immunity, 2021Co-Authors: Stephan Schneiders, Tifaine Hechard, Tomas Edgren, Kemal Avican, Maria Fällman, Anna Fahlgren, Helen WangAbstract:ABSTRACT Pathogenic Yersinia spp. depend on the activity of a potent Virulence Plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Yersinia pseudotuberculosis upregulates the Virulence Plasmid copy number (PCN) during infection and that the resulting elevated gene dose of Plasmid-encoded T3SS genes is essential for Virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the Virulence Plasmid during infection is unknown. In the present study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis Virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyer’s patches and cecum during the clonal invasive phase of the infection, while the highest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the Plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues and will be readily applicable to other infection models.
-
Spatiotemporal Variations in Growth Rate and Virulence Plasmid Copy Number during Yersinia pseudotuberculosis Infection.
Infection and immunity, 2021Co-Authors: Stephan Schneiders, Tifaine Hechard, Tomas Edgren, Kemal Avican, Maria Fällman, Anna Fahlgren, Helen WangAbstract:Pathogenic Yersinia spp. depend on the activity of a potent Virulence Plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Y. pseudotuberculosis up-regulates the Virulence Plasmid copy number (PCN) during infection and the resulting elevated gene dose of Plasmid-encoded T3SS genes is essential for Virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the Virulence Plasmid during infection is unknown. In the current study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis Virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyer's Patches and caecum during the clonal invasive phase of the infection, while the fastest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the Plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues, and will be readily applicable to other infection models.
-
Spatiotemporal Variations in Growth Rate and Virulence Plasmid Copy Number during Yersinia pseudotuberculosis Infection
2020Co-Authors: Stephan Schneiders, Tifaine Hechard, Tomas Edgren, Kemal Avican, Maria Fällman, Anna Fahlgren, Helen WangAbstract:Pathogenic Yersinia spp. depend on the activity of a potent Virulence Plasmid-encoded ysc/yop type 3 secretion system (T3SS) to colonize hosts and cause disease. It was recently shown that Y. pseudotuberculosis up-regulates the Virulence Plasmid copy number (PCN) during infection and the resulting elevated gene dose of Plasmid-encoded T3SS genes is essential for Virulence. When and how this novel regulatory mechanism is deployed and regulates the replication of the Virulence Plasmid during infection is unknown. In the current study, we applied droplet digital PCR (ddPCR) to investigate the dynamics of Y. pseudotuberculosis Virulence PCN variations and growth rates in infected mouse organs. We demonstrated that both PCN and growth varied in different tissues and over time throughout the course of infection, indicating that the bacteria adapted to discrete microenvironments during infection. The PCN was highest in Peyers Patches and caecum during the clonal invasive phase of the infection, while the fastest growth rates were found in the draining mesenteric lymph nodes. In deeper, systemic organs, the PCN was lower and more modest growth rates were recorded. Our study indicates that increased gene dosage of the Plasmid-encoded T3SS genes is most important early in the infection during invasion of the host. The described ddPCR approach will greatly simplify analyses of PCN, growth dynamics, and bacterial loads in infected tissues, and will be readily applicable to other infection models. ImportanceStudying pathogenic bacteria proliferating inside infected hosts is challenging using traditional methods, especially the transit and reversible genetic events. The bacteria are effectively diluted by the overwhelming number of host cells present in infected tissues. Using an innovative droplet digital PCR (ddPCR) approach, we have determined the Virulence Plasmid copy number (PCN) variations and growth rates of Yersinia during the course of infection in a mouse model. Here, we show that both the Virulence Plasmid copy number and bacterial growth rates display spatiotemporal variations in mice during infection. We demonstrate that the peak-to-trough ratio can be used as a proxy for determining the growth rate of invasive bacterial pathogen during infection, and ddPCR as the method of choice for quantifying DNA in host-pathogen interaction context. This proof-of-concept ddPCR approach can be easily applied for any bacterial pathogens and any infection models, for analysis of PCN, growth dynamics and bacterial loads.
