scholarly journals The Host Plant Metabolite Glucose Is the Precursor of Diffusible Signal Factor (DSF) Family Signals in Xanthomonas campestris

2015 ◽  
Vol 81 (8) ◽  
pp. 2861-2868 ◽  
Author(s):  
Yinyue Deng ◽  
Xiaoling Liu ◽  
Ji'en Wu ◽  
Jasmine Lee ◽  
Shaohua Chen ◽  
...  
Keyword(s):  
Host Plant ◽  
Virulence Factor ◽  
Xanthomonas Campestris ◽  
Ethanol Extract ◽  
Burkholderia Cenocepacia ◽  
Content Type ◽  
Communication Signal ◽  
Factor Production ◽  
Diffusible Signal Factor ◽  
Virulence Factor Production

ABSTRACTPlant pathogenXanthomonas campestrispv. campestris producescis-11-methyl-2-dodecenoic acid (diffusible signal factor [DSF]) as a cell-cell communication signal to regulate biofilm dispersal and virulence factor production. Previous studies have demonstrated that DSF biosynthesis is dependent on the presence of RpfF, an enoyl-coenzyme A (CoA) hydratase, but the DSF synthetic mechanism and the influence of the host plant on DSF biosynthesis are still not clear. We show here that exogenous addition of host plant juice or ethanol extract to the growth medium ofX. campestrispv. campestris could significantly boost DSF family signal production. It was subsequently revealed thatX. campestrispv. campestris produces not only DSF but also BDSF (cis-2-dodecenoic acid) and another novel DSF family signal, which was designated DSF-II. BDSF was originally identified inBurkholderia cenocepaciato be involved in regulation of motility, biofilm formation, and virulence inB. cenocepacia. Functional analysis suggested that DSF-II plays a role equal to that of DSF in regulation of biofilm dispersion and virulence factor production inX. campestrispv. campestris. Furthermore, chromatographic separation led to identification of glucose as a specific molecule stimulating DSF family signal biosynthesis inX. campestrispv. campestris.13C-labeling experiments demonstrated that glucose acts as a substrate to provide a carbon element for DSF biosynthesis. The results of this study indicate thatX. campestrispv. campestris could utilize a common metabolite of the host plant to enhance DSF family signal synthesis and therefore promote virulence.

scholarly journals Indole Inhibits ToxR Regulon Expression inVibrio cholerae

2019 ◽  
Vol 87 (3) ◽  
Author(s):  
Mondraya F. Howard ◽  
X. Renee Bina ◽  
James E. Bina
Keyword(s):  
Virulence Factor ◽  
Virulence Gene ◽  
Dependent Manner ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Type Vi Secretion ◽  
Biofilm Production ◽  
Factor Production ◽  
Periplasmic Domain ◽  
Virulence Factor Production

ABSTRACTIndole is a degradation product of tryptophan that functions as a signaling molecule in many bacteria. This includesVibrio cholerae, where indole was shown to regulate biofilm and type VI secretion in nontoxigenic environmental isolates. Indole is also produced by toxigenicV. choleraestrains in the human intestine, but its significance in the host is unknown. We investigated the effects of indole on toxigenicV. choleraeO1 El Tor during growth under virulence inducing conditions. The indole transcriptome was defined by RNA sequencing and showed widespread changes in the expression of genes involved in metabolism, biofilm production, and virulence factor production. In contrast, genes involved in type VI secretion were not affected by indole. We subsequently found that indole repressed genes involved inV. choleraepathogenesis, including the ToxR virulence regulon. Consistent with this, indole inhibited cholera toxin and toxin-coregulated pilus production in a dose-dependent manner. The effects of indole on virulence factor production and biofilm were linked to ToxR and the ToxR-dependent regulator LeuO. The expression ofleuOwas increased by exogenous indole and linked to repression of the ToxR virulence regulon. This process was dependent on the ToxR periplasmic domain, suggesting that indole was a ToxR agonist. This conclusion was further supported by results showing that the ToxR periplasmic domain contributed to indole-mediated increased biofilm production. Collectively, our results suggest that indole may be a niche-specific cue that can function as a ToxR agonist to modulate virulence gene expression and biofilm production inV. cholerae.

scholarly journals Staphylococcus aureus Formyl-Methionyl Transferase Mutants Demonstrate Reduced Virulence Factor Production and Pathogenicity

2013 ◽  
Vol 57 (7) ◽  
pp. 2929-2936 ◽  
Author(s):  
Thomas Lewandowski ◽  
Jianzhong Huang ◽  
Frank Fan ◽  
Shannon Rogers ◽  
Daniel Gentry ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factor ◽  
Survival Rates ◽  
Extracellular Proteins ◽  
High Survival ◽  
Invasive Infection ◽  
Loss Of Function ◽  
Content Type ◽  
Factor Production ◽  
Virulence Factor Production

ABSTRACTInhibitors of peptide deformylase (PDF) represent a new class of antibacterial agents with a novel mechanism of action. Mutations that inactivate formyl methionyl transferase (FMT), the enzyme that formylates initiator methionyl-tRNA, lead to an alternative initiation of protein synthesis that does not require deformylation and are the predominant cause of resistance to PDF inhibitors inStaphylococcus aureus. Here, we report that loss-of-function mutations in FMT impart pleiotropic effects that include a reduced growth rate, a nonhemolytic phenotype, and a drastic reduction in production of multiple extracellular proteins, including key virulence factors, such as α-hemolysin and Panton-Valentine leukocidin (PVL), that have been associated withS. aureuspathogenicity. Consequently,S. aureusFMT mutants are greatly attenuated in neutropenic and nonneutropenic murine pyelonephritis infection models and show very high survival rates compared with wild-typeS. aureus. These newly discovered effects on extracellular virulence factor production demonstrate that FMT-null mutants have a more severe fitness cost than previously anticipated, leading to a substantial loss of pathogenicity and a restricted ability to produce an invasive infection.

scholarly journals Staphylococcal Virulence Factors on the Skin of Atopic Dermatitis Patients

mSphere ◽  
2019 ◽  
Vol 4 (6) ◽  
Author(s):  
Mary C. Moran ◽  
Michael P. Cahill ◽  
Matthew G. Brewer ◽  
Takeshi Yoshida ◽  
Sara Knowlden ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Atopic Dermatitis ◽  
Virulence Factors ◽  
Virulence Factor ◽  
Protein Level ◽  
Content Type ◽  
Factor Production ◽  
First Time ◽  
Virulence Factor Production ◽  
Specific Virulence

ABSTRACT Staphylococcus aureus is the leading cause of skin and soft tissue infections, bacteremia, infective endocarditis, osteoarticular, pleuropulmonary, and device-related infections. Virulence factors secreted by S. aureus, including superantigens and cytotoxins, play significant roles in driving disease. The ability to identify virulence factors present at the site of infection will be an important tool in better identifying and understanding how specific virulence factors contribute to disease. Previously, virulence factor production has been determined by culturing S. aureus isolates and detecting the mRNA of specific virulence factors. We demonstrated for the first time that virulence factors can be directly detected at the protein level from human samples, removing the need to first culture isolated bacteria. Superantigens and cytotoxins were detected and quantified with a Western dot blot assay by using reconstituted skin swabs obtained from patients with atopic dermatitis. This methodology will significantly enhance our ability to investigate the complex host-microbe environment and the effects various therapies have on virulence factor production. Overall, the ability to directly quantify virulence factors present at the site of infection or colonization will enhance our understanding of S. aureus-related diseases and help identify optimal treatments. IMPORTANCE For the first time, we show that secreted staphylococcal virulence factors can be quantified at the protein level directly from skin swabs obtained from the skin of atopic dermatitis patients. This technique eliminates the need to culture Staphylococcus aureus and then test the strain’s potential to produce secreted virulence factors. Our methodology shows that secreted virulence factors are present on the skin of atopic patients and provides a more accurate means of evaluating the physiological impact of S. aureus in inflammatory diseases such as atopic dermatitis.

scholarly journals The Pseudomonas aeruginosa PAO1 Two-Component Regulator CarSR Regulates Calcium Homeostasis and Calcium-Induced Virulence Factor Production through Its Regulatory Targets CarO and CarP

2016 ◽  
Vol 198 (6) ◽  
pp. 951-963 ◽  
Author(s):  
Manita Guragain ◽  
Michelle M. King ◽  
Kerry S. Williamson ◽  
Ailyn C. Pérez-Osorio ◽  
Tatsuya Akiyama ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Virulence Factors ◽  
Virulence Factor ◽  
Regulatory System ◽  
Dependent Manner ◽  
Content Type ◽  
Factor Production ◽  
Two Component ◽  
Intracellular Ca ◽  
Virulence Factor Production

ABSTRACTPseudomonas aeruginosais an opportunistic human pathogen that causes severe, life-threatening infections in patients with cystic fibrosis (CF), endocarditis, wounds, or artificial implants. During CF pulmonary infections,P. aeruginosaoften encounters environments where the levels of calcium (Ca2+) are elevated. Previously, we showed thatP. aeruginosaresponds to externally added Ca2+through enhanced biofilm formation, increased production of several secreted virulence factors, and by developing a transient increase in the intracellular Ca2+level, followed by its removal to the basal submicromolar level. However, the molecular mechanisms responsible for regulating Ca2+-induced virulence factor production and Ca2+homeostasis are not known. Here, we characterized the genome-wide transcriptional response ofP. aeruginosato elevated [Ca2+] in both planktonic cultures and biofilms. Among the genes induced by CaCl2in strain PAO1 was an operon containing the two-component regulator PA2656-PA2657 (here calledcarSandcarR), while the closely related two-component regulatorsphoPQandpmrABwere repressed by CaCl2addition. To identify the regulatory targets of CarSR, we constructed a deletion mutant ofcarRand performed transcriptome analysis of the mutant strain at low and high [Ca2+]. Among the genes regulated by CarSR in response to CaCl2are the predicted periplasmic OB-fold protein, PA0320 (here calledcarO), and the inner membrane-anchored five-bladed β-propeller protein, PA0327 (here calledcarP). Mutations in bothcarOandcarPaffected Ca2+homeostasis, reducing the ability ofP. aeruginosato export excess Ca2+. In addition, a mutation incarPhad a pleotropic effect in a Ca2+-dependent manner, altering swarming motility, pyocyanin production, and tobramycin sensitivity. Overall, the results indicate that the two-component system CarSR is responsible for sensing high levels of external Ca2+and responding through its regulatory targets that modulate Ca2+homeostasis, surface-associated motility, and the production of the virulence factor pyocyanin.IMPORTANCEDuring infectious disease,Pseudomonas aeruginosaencounters environments with high calcium (Ca2+) concentrations, yet the cells maintain intracellular Ca2+at levels that are orders of magnitude less than that of the external environment. In addition, Ca2+signalsP. aeruginosato induce the production of several virulence factors. Compared to eukaryotes, little is known about how bacteria maintain Ca2+homeostasis or how Ca2+acts as a signal. In this study, we identified a two-component regulatory system inP. aeruginosaPAO1, termed CarRS, that is induced at elevated Ca2+levels. CarRS modulates Ca2+signaling and Ca2+homeostasis through its regulatory targets, CarO and CarP. The results demonstrate thatP. aeruginosauses a two-component regulatory system to sense external Ca2+and relays that information for Ca2+-dependent cellular processes.

scholarly journals Vibrio cholerae ToxR Downregulates Virulence Factor Production in Response to Cyclo(Phe-Pro)

mBio ◽  
2013 ◽  
Vol 4 (5) ◽  
Author(s):  
X. Renee Bina ◽  
Dawn L. Taylor ◽  
Amit Vikram ◽  
Vanessa M. Ante ◽  
James E. Bina
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Virulence Gene ◽  
Enteric Bacteria ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Factor Production ◽  
Virulence Regulator ◽  
Virulence Factor Production

ABSTRACTVibrio choleraeis an aquatic organism that causes the severe acute diarrheal disease cholera. The ability ofV. choleraeto cause disease is dependent upon the production of two critical virulence determinants, cholera toxin (CT) and the toxin-coregulated pilus (TCP). The expression of the genes that encode for CT and TCP production is under the control of a hierarchical regulatory system called the ToxR regulon, which functions to activate virulence gene expression in response toin vivostimuli. Cyclic dipeptides have been found to be produced by numerous bacteria, yet their biological function remains unknown.V. choleraehas been shown to produce cyclo(Phe-Pro). Previous studies in our laboratory demonstrated that cyclo(Phe-Pro) inhibitedV. choleraevirulence factor production. For this study, we report on the mechanism by which cyclo(Phe-Pro) inhibited virulence factor production. We have demonstrated that exogenous cyclo(Phe-Pro) activated the expression ofleuO, a LysR-family regulator that had not been previously associated withV. choleraevirulence. IncreasedleuOexpression repressedaphAtranscription, which resulted in downregulation of the ToxR regulon and attenuated CT and TCP production. The cyclo(Phe-Pro)-dependent induction ofleuOexpression was found to be dependent upon the virulence regulator ToxR. Cyclo(Phe-Pro) did not affecttoxRtranscription or ToxR protein levels but appeared to enhance the ToxR-dependent transcription ofleuO. These results have identifiedleuOas a new component of the ToxR regulon and demonstrate for the first time that ToxR is capable of downregulating virulence gene expression in response to an environmental cue.IMPORTANCEThe ToxR regulon has been a focus of cholera research for more than three decades. During this time, a model has emerged wherein ToxR functions to activate the expression ofVibrio choleraevirulence factors upon host entry.V. choleraeand other enteric bacteria produce cyclo(Phe-Pro), a cyclic dipeptide that we identified as an inhibitor ofV. choleraevirulence factor production. This finding suggested that cyclo(Phe-Pro) was a negative effector of virulence factor production and represented a molecule that could potentially be exploited for therapeutic development. In this work, we investigated the mechanism by which cyclo(Phe-Pro) inhibited virulence factor production. We found that cyclo(Phe-Pro) signaled through ToxR to activate the expression ofleuO, a new virulence regulator that functioned to repress virulence factor production. Our results have identified a new arm of the ToxR regulon and suggest that ToxR may play a broader role in pathogenesis than previously known.

scholarly journals Vibrio cholerae OmpR Represses the ToxR Regulon in Response to Membrane Intercalating Agents That Are Prevalent in the Human Gastrointestinal Tract

2019 ◽  
Vol 88 (3) ◽  
Author(s):  
D. E. Kunkle ◽  
T. F. Bina ◽  
X. R. Bina ◽  
J. E. Bina
Keyword(s):  
Gastrointestinal Tract ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Diarrheal Disease ◽  
Multidrug Efflux ◽  
Content Type ◽  
Factor Production ◽  
Resistance Nodulation Division ◽  
Intercalating Agents ◽  
Virulence Factor Production

ABSTRACT Multidrug efflux systems belonging to the resistance-nodulation-division (RND) superfamily are ubiquitous in Gram-negative bacteria. RND efflux systems are often associated with multiple antimicrobial resistance and also contribute to the expression of diverse bacterial phenotypes including virulence, as documented in the intestinal pathogen Vibrio cholerae, the causative agent of the severe diarrheal disease cholera. Transcriptomic studies with RND efflux-negative V. cholerae suggested that RND-mediated efflux was required for homeostasis, as loss of RND efflux resulted in the activation of transcriptional regulators, including multiple environmental sensing systems. In this report, we investigated six RND efflux-responsive regulatory genes for contributions to V. cholerae virulence factor production. Our data showed that the V. cholerae gene VC2714, encoding a homolog of Escherichia coli OmpR, was a virulence repressor. The expression of ompR was elevated in an RND-null mutant, and ompR deletion partially restored virulence factor production in the RND-negative background. Virulence inhibitory activity in the RND-negative background resulted from OmpR repression of the key ToxR regulon virulence activator aphB, and ompR overexpression in wild-type cells also repressed virulence through aphB. We further show that ompR expression was not altered by changes in osmolarity but instead was induced by membrane-intercalating agents that are prevalent in the host gastrointestinal tract and which are substrates of the V. cholerae RND efflux systems. Our collective results indicate that V. cholerae ompR is an aphB repressor and regulates the expression of the ToxR virulence regulon in response to novel environmental cues.

scholarly journals Development of anEx VivoPorcine Lung Model for Studying Growth, Virulence, and Signaling of Pseudomonas aeruginosa

2014 ◽  
Vol 82 (8) ◽  
pp. 3312-3323 ◽  
Author(s):  
Freya Harrison ◽  
Aneesha Muruli ◽  
Steven Higgins ◽  
Stephen P. Diggle
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Virulence Factor ◽  
Ex Vivo ◽  
Homoserine Lactone ◽  
Lung Model ◽  
Content Type ◽  
Evolutionary Forces ◽  
Factor Production ◽  
Virulence Factor Production

ABSTRACTResearch into chronic infection by bacterial pathogens, such asPseudomonas aeruginosa, uses variousin vitroand live host models. While these have increased our understanding of pathogen growth, virulence, and evolution, each model has certain limitations.In vitromodels cannot recapitulate the complex spatial structure of host organs, while experiments on live hosts are limited in terms of sample size and infection duration for ethical reasons; live mammal models also require specialized facilities which are costly to run. To address this, we have developed anex vivopig lung (EVPL) model for quantifyingPseudomonas aeruginosagrowth, quorum sensing (QS), virulence factor production, and tissue damage in an environment that mimics a chronically infected cystic fibrosis (CF) lung. In a first test of our model, we show thatlasRmutants, which do not respond to 3-oxo-C12-homoserine lactone (HSL)-mediated QS, exhibit reduced virulence factor production in EVPL. We also show thatlasRmutants grow as well as or better than a corresponding wild-type strain in EVPL.lasRmutants frequently and repeatedly arise during chronic CF lung infection, but the evolutionary forces governing their appearance and spread are not clear. Our data are not consistent with the hypothesis thatlasRmutants act as social “cheats” in the lung; rather, our results support the hypothesis thatlasRmutants are more adapted to the lung environment. More generally, this model will facilitate improved studies of microbial disease, especially studies of how cells of the same and different species interact in polymicrobial infections in a spatially structured environment.

scholarly journals Genetic Interference Analysis Reveals that Both 3-Hydroxybenzoic Acid and 4-Hydroxybenzoic Acid Are Involved in Xanthomonadin Biosynthesis in the Phytopathogen Xanthomonas campestris pv. campestris

2020 ◽  
Vol 110 (2) ◽  
pp. 278-286
Author(s):  
Xue-Qiang Cao ◽  
Xing-Yu Ouyang ◽  
Bo Chen ◽  
Kai Song ◽  
Lian Zhou ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Virulence Factor ◽  
Xanthomonas Campestris ◽  
Gene Clusters ◽  
Hydroxybenzoic Acid ◽  
Factor Production ◽  
In The Wild ◽  
Genetic Interference ◽  
Xanthomonas Campestris Pv Campestris ◽  
Virulence Factor Production

A characteristic feature of phytopathogenic Xanthomonas bacteria is the production of yellow membrane-bound pigments called xanthomonadins. Previous studies showed that 3-hydroxybenzoic acid (3-HBA) was a xanthomonadin biosynthetic intermediate and also, that it had a signaling role. The question of whether the structural isomers 4-HBA and 2-HBA (salicylic acid) have any role in xanthomonadin biosynthesis remained unclear. In this study, we have selectively eliminated 3-HBA, 4-HBA, or the production of both by expression of the mhb, pobA, and pchAB gene clusters in the Xanthomonas campestris pv. campestris strain XC1. The resulting strains were different in pigmentation, virulence factor production, and virulence. These results suggest that both 3-HBA and 4-HBA are involved in xanthomonadin biosynthesis. When both 3-HBA and 4-HBA are present, X. campestris pv. campestris prefers 3-HBA for Xanthomonadin-A biosynthesis; the 3-HBA–derived Xanthomonadin-A was predominant over the 4-HBA–derived xanthomonadin in the wild-type strain XC1. If 3-HBA is not present, then 4-HBA is used for biosynthesis of a structurally uncharacterized Xanthomonadin-B. Salicylic acid had no effect on xanthomonadin biosynthesis. Interference with 3-HBA and 4-HBA biosynthesis also affected X. campestris pv. campestris virulence factor production and reduced virulence in cabbage and Chinese radish. These findings add to our understanding of xanthomonadin biosynthetic mechanisms and further help to elucidate the biological roles of xanthomonadins in X. campestris pv. campestris adaptation and virulence in host plants.

scholarly journals Xanthomonas campestris Promotes Diffusible Signal Factor Biosynthesis and Pathogenicity by Utilizing Glucose and Sucrose from Host Plants

2019 ◽  
Vol 32 (2) ◽  
pp. 157-166 ◽  
Author(s):  
Chunyan Zhang ◽  
Mingfa Lv ◽  
Wenfang Yin ◽  
Tingyan Dong ◽  
Changqing Chang ◽  
...  
Keyword(s):  
Host Plant ◽  
Xanthomonas Campestris ◽  
Infection Process ◽  
Plant Metabolites ◽  
Multiple Strategies ◽  
Exogenous Addition ◽  
Diffusible Signal Factor ◽  
Signal Production ◽  
Induced Changes ◽  
Encoding Genes

The plant pathogen Xanthomonas campestris pv. campestris produces diffusible signal factor (DSF) quorum sensing (QS) signals to regulate its biological functions and virulence. Our previous study showed that X. campestris pv. campestris utilizes host plant metabolites to enhance the biosynthesis of DSF family signals. However, it is unclear how X. campestris pv. campestris benefits from the metabolic products of the host plant. In this study, we observed that the host plant metabolites not only boosted the production of the DSF family signals but also modulated the expression levels of DSF-regulated genes in X. campestris pv. campestris. Infection with X. campestris pv. campestris induced changes in the expression of many sugar transporter genes in Arabidopsis thaliana. Exogenous addition of sucrose or glucose, which are the major products of photosynthesis in plants, enhanced DSF signal production and X. campestris pv. campestris pathogenicity in the Arabidopsis model. In addition, several sucrose hydrolase–encoding genes in X. campestris pv. campestris and sucrose invertase–encoding genes in the host plant were notably upregulated during the infection process. These enzymes hydrolyzed sucrose to glucose and fructose, and in trans expression of one of these enzymes, CINV1 of A. thaliana or XC_0805 of X. campestris pv. campestris, enhanced DSF signal biosynthesis in X. campestris pv. campestris in the presence of sucrose. Taken together, our findings demonstrate that X. campestris pv. campestris applies multiple strategies to utilize host plant sugars to enhance QS and pathogenicity.

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