scholarly journals Activation of theListeria monocytogenesVirulence Program by a Reducing Environment

mBio ◽  
2017 ◽  
Vol 8 (5) ◽  
Author(s):  
Jonathan L. Portman ◽  
Samuel B. Dubensky ◽  
Bret N. Peterson ◽  
Aaron T. Whiteley ◽  
Daniel A. Portnoy
Keyword(s):  
Gene Expression ◽  
Synthetic Medium ◽  
Virulence Gene ◽  
Intracellular Pathogen ◽  
Intracellular Pathogens ◽  
Virulence Gene Expression ◽  
Cell Cytosol ◽  
Host Cell Cytosol

ABSTRACTUpon entry into the host cell cytosol, the facultative intracellular pathogenListeria monocytogenescoordinates the expression of numerous essential virulence factors by allosteric binding of glutathione (GSH) to the Crp-Fnr family transcriptional regulator PrfA. Here, we report that robust virulence gene expression can be recapitulated by growing bacteria in a synthetic medium containing GSH or other chemical reducing agents. Bacteria grown under these conditions were 45-fold more virulent in an acute murine infection model and conferred greater immunity to a subsequent lethal challenge than bacteria grown in conventional media. During cultivationin vitro, PrfA activation was completely dependent on the intracellular levels of GSH, as a glutathione synthase mutant (ΔgshF) was activated by exogenous GSH but not reducing agents. PrfA activation was repressed in a synthetic medium supplemented with oligopeptides, but the repression was relieved by stimulation of the stringent response. These data suggest that cytosolicL. monocytogenesinterprets a combination of metabolic and redox cues as a signal to initiate robust virulence gene expressionin vivo.IMPORTANCEIntracellular pathogens are responsible for much of the worldwide morbidity and mortality from infectious diseases. These pathogens have evolved various strategies to proliferate within individual cells of the host and avoid the host immune response. Through cellular invasion or the use of specialized secretion machinery, all intracellular pathogens must access the host cell cytosol to establish their replicative niches. Determining how these pathogens sense and respond to the intracellular compartment to establish a successful infection is critical to our basic understanding of the pathogenesis of each organism and for the rational design of therapeutic interventions.Listeria monocytogenesis a model intracellular pathogen with robustin vitroandin vivoinfection models. Studies of the host-sensing and downstream signaling mechanisms evolved byL. monocytogenesoften describe themes of pathogenesis that are broadly applicable to less tractable pathogens. Here, we describe how bacteria use external redox states as a cue to activate virulence.

Vibrio harveyi virulence gene expression in vitro and in vivo during infection in black tiger shrimp Penaeus monodon

2020 ◽  
Vol 139 ◽  
pp. 153-160
Author(s):  
S Peeralil ◽  
TC Joseph ◽  
V Murugadas ◽  
PG Akhilnath ◽  
VN Sreejith ◽  
...  
Keyword(s):  
Gene Expression ◽  
Virulence Genes ◽  
Vibrio Harveyi ◽  
Penaeus Monodon ◽  
Challenge Test ◽  
Virulence Gene ◽  
Economic Losses ◽  
Virulence Gene Expression

Luminescent Vibrio harveyi is common in sea and estuarine waters. It produces several virulence factors and negatively affects larval penaeid shrimp in hatcheries, resulting in severe economic losses to shrimp aquaculture. Although V. harveyi is an important pathogen of shrimp, its pathogenicity mechanisms have yet to be completely elucidated. In the present study, isolates of V. harveyi were isolated and characterized from diseased Penaeus monodon postlarvae from hatcheries in Kerala, India, from September to December 2016. All 23 tested isolates were positive for lipase, phospholipase, caseinase, gelatinase and chitinase activity, and 3 of the isolates (MFB32, MFB71 and MFB68) showed potential for significant biofilm formation. Based on the presence of virulence genes, the isolates of V. harveyi were grouped into 6 genotypes, predominated by vhpA+ flaB+ ser+ vhh1- luxR+ vopD- vcrD+ vscN-. One isolate from each genotype was randomly selected for in vivo virulence experiments, and the LD50 ranged from 1.7 ± 0.5 × 103 to 4.1 ± 0.1 × 105 CFU ml-1. The expression of genes during the infection in postlarvae was high in 2 of the isolates (MFB12 and MFB32), consistent with the result of the challenge test. However, in MFB19, even though all genes tested were present, their expression level was very low and likely contributed to its lack of virulence. Because of the significant variation in gene expression, the presence of virulence genes alone cannot be used as a marker for pathogenicity of V. harveyi.

scholarly journals 18β-Glycyrrhetinic Acid Inhibits Methicillin-Resistant Staphylococcus aureus Survival and Attenuates Virulence Gene Expression

2012 ◽  
Vol 57 (1) ◽  
pp. 241-247 ◽  
Author(s):  
Danyelle R. Long ◽  
Julia Mead ◽  
Jay M. Hendricks ◽  
Michele E. Hardy ◽  
Jovanka M. Voyich
Keyword(s):  
Gene Expression ◽  
Staphylococcus Aureus ◽  
Virulence Gene ◽  
Glycyrrhetinic Acid ◽  
Licorice Root ◽  
Methicillin Resistant ◽  
Content Type ◽  
Virulence Gene Expression

ABSTRACTMethicillin-resistantStaphylococcus aureus(MRSA) has become a major source of infection in hospitals and in the community. Increasing antibiotic resistance inS. aureusstrains has created a need for alternative therapies to treat disease. A component of the licorice rootGlycyrrhizaspp., 18β-glycyrrhetinic acid (GRA), has been shown to have antiviral, antitumor, and antibacterial activity. This investigation explores thein vitroandin vivoeffects of GRA on MRSA pulsed-field gel electrophoresis (PFGE) type USA300. GRA exhibited bactericidal activity at concentrations exceeding 0.223 μM. Upon exposure ofS. aureusto sublytic concentrations of GRA, we observed a reduction in expression of key virulence genes, includingsaeRandhla. In murine models of skin and soft tissue infection, topical GRA treatment significantly reduced skin lesion size and decreased the expression ofsaeRandhlagenes. Our investigation demonstrates that at high concentrations GRA is bactericidal to MRSA and at sublethal doses it reduces virulence gene expression inS. aureusbothin vitroandin vivo.

scholarly journals Genome-Wide Identification of Genes Regulated by the Rcs Phosphorelay System in Erwinia amylovora

2012 ◽  
Vol 25 (1) ◽  
pp. 6-17 ◽  
Author(s):  
Dongping Wang ◽  
Mingsheng Qi ◽  
Bernarda Calla ◽  
Schuyler S. Korban ◽  
Steven J. Clough ◽  
...  
Keyword(s):  
Gene Expression ◽  
Erwinia Amylovora ◽  
Virulence Gene ◽  
Luria Bertani ◽  
Regulatory Genes ◽  
Bacterial Cells ◽  
Virulence Gene Expression ◽  
Genome Wide

The exopolysaccharide amylovoran is one of the major pathogenicity factors in Erwinia amylovora, the causal agent of fire blight of apples and pears. We have previously demonstrated that the RcsBCD phosphorelay system is essential for virulence by controlling amylovoran biosynthesis. We have also found that the hybrid sensor kinase RcsC differentially regulates amylovoran production in vitro and in vivo. To further understand how the Rcs system regulates E. amylovora virulence gene expression, we conducted genome-wide microarray analyses to determine the regulons of RcsB and RcsC in liquid medium and on immature pear fruit. Array analyses identified a total of 648 genes differentially regulated by RcsCB in vitro and in vivo. Consistent with our previous findings, RcsB acts as a positive regulator in both conditions, while RcsC positively controls expression of amylovoran biosynthetic genes in vivo but negatively controls expression in vitro. Besides amylovoran biosynthesis and regulatory genes, cell-wall and cell-envelope (membrane) as well as regulatory genes were identified as the major components of the RcsBC regulon, including many novel genes. We have also demonstrated that transcripts of rcsA, rcsC, and rcsD genes but not the rcsB gene were up-regulated when bacterial cells were grown in minimal medium or following infection of pear fruits compared with those grown in Luria Bertani medium. Furthermore, using the genome of E. amylovora ATCC 49946, a hidden Markov model predicted 60 genes with a candidate RcsB binding site in the intergenic region, 28 of which were identified in the microarray assay. Based on these findings as well as previous reported data, a working model has been proposed to illustrate how the Rcs phosphorelay system regulates virulence gene expression in E. amylovora.

scholarly journals A Systems Biology Approach To Modeling Vibrio cholerae Gene Expression under Virulence-Inducing Conditions

2010 ◽  
Vol 192 (17) ◽  
pp. 4300-4310 ◽  
Author(s):  
Sanjat Kanjilal ◽  
Robert Citorik ◽  
Regina C. LaRocque ◽  
Marco F. Ramoni ◽  
Stephen B. Calderwood
Keyword(s):  
Gene Expression ◽  
Systems Biology ◽  
Vibrio Cholerae ◽  
Regulation Of Gene Expression ◽  
Virulence Gene ◽  
Temporal Separation ◽  
New Members ◽  
Virulence Gene Expression

ABSTRACT Vibrio cholerae is a Gram-negative bacillus that is the causative agent of cholera. Pathogenesis in vivo occurs through a series of spatiotemporally controlled events under the control of a gene cascade termed the ToxR regulon. Major genes in the ToxR regulon include the master regulators toxRS and tcpPH, the downstream regulator toxT, and virulence factors, the ctxAB and tcpA operons. Our current understanding of the dynamics of virulence gene expression is limited to microarray analyses of expression at selected time points. To better understand this process, we utilized a systems biology approach to examine the temporal regulation of gene expression in El Tor V. cholerae grown under virulence-inducing conditions in vitro (AKI medium), using high-resolution time series genomic profiling. Results showed that overall gene expression in AKI medium mimics that of in vivo studies but with less clear temporal separation between upstream regulators and downstream targets. Expression of toxRS was unaffected by growth under virulence-inducing conditions, but expression of toxT was activated shortly after switching from stationary to aerating conditions. The tcpA operon was also activated early during mid-exponential-phase growth, while the ctxAB operon was turned on later, after the rise in toxT expression. Expression of ctxAB continued to rise despite an eventual decrease in toxT. Cluster analysis of gene expression highlighted 15 hypothetical genes and six genes related to environmental information processing that represent potential new members of the ToxR regulon. This study applies systems biology tools to analysis of gene expression of V. cholerae in vitro and provides an important comparator for future studies done in vivo.

scholarly journals Pneumococcal Virulence Gene Expression and Host Cytokine Profiles during Pathogenesis of Invasive Disease

2007 ◽  
Vol 76 (2) ◽  
pp. 646-657 ◽  
Author(s):  
Layla K. Mahdi ◽  
Abiodun D. Ogunniyi ◽  
Kim S. LeMessurier ◽  
James C. Paton
Keyword(s):  
Gene Expression ◽  
Expression Patterns ◽  
Virulence Gene ◽  
Invasive Disease ◽  
Gene Expression Patterns ◽  
Putative Virulence Factor ◽  
Necrosis Factor Alpha ◽  
Virulence Gene Expression

ABSTRACTPneumococcal disease continues to account for significant morbidity and mortality worldwide. For the development of novel prophylactic and therapeutic strategies against the disease spectrum, a complete understanding of pneumococcal behavior in vivo is necessary. We evaluated the expression patterns of the proven and putative virulence factor genesadcR,cbpA,cbpD,cbpG,cpsA,nanA,pcpA,piaA,ply,psaA,pspA, andspxBafter intranasal infection of CD1 mice with serotype 2, 4, and 6A pneumococci by real-time reverse transcription-PCR. Simultaneous gene expression patterns of selected host immunomodulatory molecules, CCL2, CCL5, CD54, CXCL2, interleukin-6, and tomor necrosis factor alpha, were also investigated. We show that pneumococcal virulence genes are differentially expressed in vivo, with some genes demonstrating niche- and serotype-specific differential expression. The in vivo expression patterns could not be attributed to in vitro differences in expression of the genes in transparent and opaque variants of the three strains. The host molecules were significantly upregulated, especially in the lungs, blood, and brains of mice. The pneumococcal-gene expression patterns support their ascribed roles in pathogenesis, providing insight into which protein combinations might be more appropriate as vaccine antigens against invasive disease. This is the first simultaneous comparison of bacterial- and host gene expression in the same animal during pathogenesis. The strategy provides a platform for prospective evaluation of interaction kinetics between invading pneumococci and human patients in culture-positive cases and should be feasible in other infection models.

scholarly journals Virulence gene regulation inside and outside

2000 ◽  
Vol 355 (1397) ◽  
pp. 657-665 ◽  
Author(s):  
Victor J. DiRita ◽  
N. Cary Engleberg ◽  
Andrew Heath ◽  
Alita Miller ◽  
J. Adam Crawford ◽  
...  
Keyword(s):  
Gene Expression ◽  
Gene Regulation ◽  
Regulatory System ◽  
Virulence Gene ◽  
Virulence Gene Expression ◽  
Regulatory Cascade ◽  
Transcription Activators ◽  
Regulated Gene Expression

Much knowledge about microbial gene regulation and virulence is derived from genetic and biochemical studies done outside of hosts. The aim of this review is to correlate observations made in vitro and in vivo with two different bacterial pathogens in which the nature of regulated gene expression leading to virulence is quite different. The first is Vibrio cholerae , in which the concerted action of a complicated regulatory cascade involving several transcription activators leads ultimately to expression of cholera toxin and the toxin–coregulated pilus. The regulatory cascade is active in vivo and is also required for maintenance of V . cholerae in the intestinal tract during experimental infection. Nevertheless, specific signals predicted to be generated in vivo , such as bile and a temperature of 37°C, have a severe downmodulating effect on activation of toxin and pilus expression. Another unusual aspect of gene regulation in this system is the role played by inner membrane proteins that activate transcription. Although the topology of these proteins suggests an appealing model for signal transduction leading to virulence gene expression, experimental evidence suggests that such a model may be simplistic. In Streptococcus pyogenes , capsule production is critical for virulence in an animal model of necrotizing skin infection. Yet capsule is apparently produced to high levels only from mutation in a two–component regulatory system, CsrR and CsrS. Thus it seems that in V . cholerae a complex regulatory pathway has evolved to control virulence by induction of gene expression in vivo , whereas in S. pyogenes at least one mode of pathogenicity is potentiated by the absence of regulation.

Quorum sensing regulation of virulence gene expression in Vibrio harveyi in vitro and in vivo during infection of gnotobiotic brine shrimp larvae

2011 ◽  
Vol 3 (5) ◽  
pp. 597-602 ◽  
Author(s):  
H. A. Darshanee Ruwandeepika ◽  
Patit Paban Bhowmick ◽  
Indrani Karunasagar ◽  
Peter Bossier ◽  
Tom Defoirdt
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Brine Shrimp ◽  
Vibrio Harveyi ◽  
Virulence Gene ◽  
Virulence Gene Expression

Virulence gene expression in vivo

2004 ◽  
Vol 7 (3) ◽  
pp. 283-289 ◽  
Author(s):  
S SHELBURNE ◽  
J MUSSER
Keyword(s):  
Gene Expression ◽  
Virulence Gene ◽  
Virulence Gene Expression

scholarly journals Role of BrnQ1 and BrnQ2 in Branched-Chain Amino Acid Transport and Virulence in Staphylococcus aureus

2014 ◽  
Vol 83 (3) ◽  
pp. 1019-1029 ◽  
Author(s):  
Julienne C. Kaiser ◽  
Sameha Omer ◽  
Jessica R. Sheldon ◽  
Ian Welch ◽  
David E. Heinrichs
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Gene ◽  
Defined Medium ◽  
Infection Model ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Branched Chain Amino Acid ◽  
Branched Chain

The branched-chain amino acids (BCAAs; Ile, Leu, and Val) not only are important nutrients for the growth ofStaphylococcus aureusbut also are corepressors for CodY, which regulates virulence gene expression, implicating BCAAs as an important link between the metabolic state of the cell and virulence. BCAAs are either synthesized intracellularly or acquired from the environment.S. aureusencodes three putative BCAA transporters, designated BrnQ1, BrnQ2, and BrnQ3; their functions have not yet been formally tested. In this study, we mutated all threebrnQparalogs so as to characterize their substrate specificities and their roles in growthin vitroandin vivo. We demonstrated that in the community-associated, methicillin-resistantS. aureus(CA-MRSA) strain USA300, BrnQ1 is involved in uptake of all three BCAAs, BrnQ2 transports Ile, and BrnQ3 does not have a significant role in BCAA transport under the conditions tested. Of the three, only BrnQ1 is essential for USA300 to grow in a chemically defined medium that is limited for Leu or Val. Interestingly, we observed that abrnQ2mutant grew better than USA300 in media limited for Leu and Val, owing to the fact that this mutation leads to overexpression ofbrnQ1. In a murine infection model, thebrnQ1mutant was attenuated, but in contrast,brnQ2mutants had significantly increased virulence compared to that of USA300, a phenotype we suggest is at least partially linked to enhancedin vivoscavenging of Leu and Val through BrnQ1. These data uncover a hitherto-undiscovered connection between nutrient acquisition and virulence in CA-MRSA.

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