scholarly journals Identification of Novel Thermosensors in Gram-Positive Pathogens

2020 ◽  
Vol 7 ◽  
Author(s):  
Pilar Fernández ◽  
Alejandra Raquel Díaz ◽  
María Florencia Ré ◽  
Lucía Porrini ◽  
Diego de Mendoza ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Response Regulator ◽  
Physiological Mechanism ◽  
Virulence Gene ◽  
Membrane Lipid ◽  
Gram Positive ◽  
Virulence Gene Expression ◽  
Cognate Response Regulator

Temperature is a crucial variable that every living organism, from bacteria to humans, need to sense and respond to in order to adapt and survive. In particular, pathogenic bacteria exploit host-temperature sensing as a cue for triggering virulence gene expression. Here, we have identified and characterized two integral membrane thermosensor histidine kinases (HKs) from Gram-positive pathogens that exhibit high similarity to DesK, the extensively characterized cold sensor histidine kinase from Bacillus subtilis. Through in vivo experiments, we demonstrate that SA1313 from Staphylococcus aureus and BA5598 from Bacillus anthracis, which likely control the expression of putative ATP binding cassette (ABC) transporters, are regulated by environmental temperature. We show here that these HKs can phosphorylate the non-cognate response regulator DesR, partner of DesK, both in vitro and in vivo, inducing in B. subtilis the expression of the des gene upon a cold shock. In addition, we report the characterization of another DesK homolog from B. subtilis, YvfT, also closely associated to an ABC transporter. Although YvfT phosphorylates DesR in vitro, this sensor kinase can only induce des expression in B. subtilis when overexpressed together with its cognate response regulator YvfU. This finding evidences a physiological mechanism to avoid cross talk with DesK after a temperature downshift. Finally, we present data suggesting that the HKs studied in this work appear to monitor different ranges of membrane lipid properties variations to mount adaptive responses upon cooling. Overall, our findings point out that bacteria have evolved sophisticated mechanisms to assure specificity in the response to environmental stimuli. These findings pave the way to understand thermosensing mediated by membrane proteins that could have important roles upon host invasion by bacterial pathogens.

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 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.

scholarly journals TSPphg Lysin from the Extremophilic Thermus Bacteriophage TSP4 as a Potential Antimicrobial Agent against Both Gram-Negative and Gram-Positive Pathogenic Bacteria

Viruses ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 192 ◽  
Author(s):  
Feng Wang ◽  
Xinyu Ji ◽  
Qiupeng Li ◽  
Guanling Zhang ◽  
Jiani Peng ◽  
...  
Keyword(s):  
Bacterial Infections ◽  
Pathogenic Bacteria ◽  
Infection Model ◽  
Bacterial Cells ◽  
Skin Damage ◽  
Gram Positive ◽  
Antibiotic Resistant ◽  
Gram Negative

New strategies against antibiotic-resistant bacterial pathogens are urgently needed but are not within reach. Here, we present in vitro and in vivo antimicrobial activity of TSPphg, a novel phage lysin identified from extremophilic Thermus phage TSP4 by sequencing its whole genome. By breaking down the bacterial cells, TSPphg is able to cause bacteria destruction and has shown bactericidal activity against both Gram-negative and Gram-positive pathogenic bacteria, especially antibiotic-resistant strains of Klebsiella pneumoniae, in which the complete elimination and highest reduction in bacterial counts by greater than 6 logs were observed upon 50 μg/mL TSPphg treatment at 37 °C for 1 h. A murine skin infection model further confirmed the in vivo efficacy of TSPphg in removing a highly dangerous and multidrug-resistant Staphylococcus aureus from skin damage and in accelerating wound closure. Together, our findings may offer a therapeutic alternative to help fight bacterial infections in the current age of mounting antibiotic resistance, and to shed light on bacteriophage-based strategies to develop novel anti-infectives.

scholarly journals Joint Transcriptional Control of xpsR, the Unusual Signal Integrator of the Ralstonia solanacearum Virulence Gene Regulatory Network, by a Response Regulator and a LysR-Type Transcriptional Activator

1998 ◽  
Vol 180 (10) ◽  
pp. 2736-2743 ◽  
Author(s):  
Jianzhong Huang ◽  
Wandee Yindeeyoungyeon ◽  
Ram P. Garg ◽  
Timothy P. Denny ◽  
Mark A. Schell
Keyword(s):  
Binding Site ◽  
Transcriptional Control ◽  
Response Regulator ◽  
Consensus Sequence ◽  
Virulence Gene ◽  
Transcriptional Activator ◽  
Binding Assays ◽  
Environmental Signals

ABSTRACT Ralstonia (Pseudomonas)solanacearum is a soil-borne phytopathogen that causes a wilting disease of many important crops. It makes large amounts of the exopolysaccharide EPS I, which it requires for efficient colonization, wilting, and killing of plants. Transcription of the epsoperon, encoding biosynthetic enzymes for EPS I, is controlled by a unique and complex sensory network that responds to multiple environmental signals. This network is comprised of the novel transcriptional activator XpsR, three distinct two-component regulatory systems (VsrAD, VsrBC, and PhcSR), and the LysR-type regulator PhcA, which is under the control of PhcSR. Here we show that thexpsR promoter (P xpsR ) is simultaneously controlled by PhcA and VsrD, permitting XpsR to act like a signal integrator, simultaneously coordinating signal input into theeps promoter from both VsrAD and PhcSR. Additionally, we used in vivo expression analysis and in vitro DNA binding assays with substitution and deletion mutants of P xpsR to show the following. (i) PhcA primarily interacts with a typical 14-bp LysR-type consensus sequence around position −77, causing a sixfold activation of P xpsR ; a weaker, less-defined binding site between −183 and −239 likely enhances PhcA binding and activation via the −77 site another twofold. (ii) Full 70-fold activation of P xpsR requires the additional interaction of the VsrD response regulator (or its surrogate) with a 14-bp dyadic sequence centered around −315 where it enhances activation (and possibly binding) by PhcA; however, VsrD alone cannot activate P xpsR . (iii) Increasing the distance between the putative VsrD binding site from that of PhcA by up to 232 bp did not dramatically affect P xpsR activation or regulation.

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 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.

scholarly journals QseC inhibition as an antivirulence approach for colitis-associated bacteria

2016 ◽  
Vol 114 (1) ◽  
pp. 142-147 ◽  
Author(s):  
Michelle G. Rooks ◽  
Patrick Veiga ◽  
Analise Z. Reeves ◽  
Sydney Lavoie ◽  
Koji Yasuda ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Intestinal Inflammation ◽  
Virulence Gene ◽  
Susceptible Host ◽  
Virulence Gene Expression ◽  
Bacterial Signaling ◽  
Two Component ◽  
Sense And Respond

Hosts and their microbes have established a sophisticated communication system over many millennia. Within mammalian hosts, this dynamic cross-talk is essential for maintaining intestinal homeostasis. In a genetically susceptible host, dysbiosis of the gut microbiome and dysregulated immune responses are central to the development of inflammatory bowel disease (IBD). Previous surveys of stool from theT-bet−/−Rag2−/−IBD mouse model revealed microbial features that discriminate between health and disease states. Enterobacteriaceae expansion and increased gene abundances for benzoate degradation, two-component systems, and bacterial motility proteins pointed to the potential involvement of a catecholamine-mediated bacterial signaling axis in colitis pathogenesis. Enterobacteriaceae sense and respond to microbiota-generated signals and host-derived catecholamines through the two-component quorum-sensingEscherichia coliregulators B and C (QseBC) system. On signal detection, QseC activates a cascade to induce virulence gene expression. Although a single pathogen has not been identified as a causative agent in IBD, adherent-invasiveEscherichia coli(AIEC) have been implicated. Flagellar expression is necessary for the IBD-associated AIEC strain LF82 to establish colonization. Thus, we hypothesized thatqseCinactivation could reduce LF82’s virulence, and found that an absence ofqseCleads to down-regulated flagellar expression and motility in vitro and reduced colonization in vivo. We extend these findings on the potential of QseC-based IBD therapeutics to three preclinical IBD models, wherein we observe that QseC blockade can effectively modulate colitogenic microbiotas to reduce intestinal inflammation. Collectively, our data support a role for QseC-mediated bacterial signaling in IBD pathogenesis and indicate that QseC inhibition may be a useful microbiota-targeted approach for disease management.

scholarly journals Role of RelA and SpoT in Burkholderia pseudomallei Virulence and Immunity

2012 ◽  
Vol 80 (9) ◽  
pp. 3247-3255 ◽  
Author(s):  
Claudia M. Müller ◽  
Laura Conejero ◽  
Natasha Spink ◽  
Matthew E. Wand ◽  
Gregory J. Bancroft ◽  
...  
Keyword(s):  
Burkholderia Pseudomallei ◽  
Galleria Mellonella ◽  
Bacterial Species ◽  
Virulence Gene ◽  
Live Attenuated Vaccine ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Control And Prevention

ABSTRACTBurkholderia pseudomalleiis a Gram-negative soil bacterium and the causative agent of melioidosis, a disease of humans and animals. It is also listed as a category B bioterrorism threat agent by the U.S. Centers for Disease Control and Prevention, and there is currently no melioidosis vaccine available. Small modified nucleotides such as the hyperphosphorylated guanosine molecules ppGpp and pppGpp play an important role as signaling molecules in prokaryotes. They mediate a global stress response under starvation conditions and have been implicated in the regulation of virulence and survival factors in many bacterial species. In this study, we created arelA spoTdouble mutant inB. pseudomalleistrain K96243, which lacks (p)ppGpp-synthesizing enzymes, and investigated its phenotypein vitroandin vivo. TheB. pseudomalleiΔrelAΔspoTmutant displayed a defect in stationary-phase survival and intracellular replication in murine macrophages. Moreover, the mutant was attenuated in theGalleria mellonellainsect model and in both acute and chronic mouse models of melioidosis. Vaccination of mice with the ΔrelAΔspoTmutant resulted in partial protection against infection with wild-typeB. pseudomallei. In summary, (p)ppGpp signaling appears to represent an essential component of the regulatory network governing virulence gene expression and stress adaptation inB. pseudomallei, and the ΔrelAΔspoTmutant may be a promising live-attenuated vaccine candidate.

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 Application of nano-curcumin as a natural antimicrobial agent against Gram-positive pathogens

2021 ◽  
Vol 13 (1) ◽  
pp. 110-126
Author(s):  
Ruchi Sankhwar ◽  
Shilpi Yadav ◽  
Abhishek Kumar ◽  
Ravi Kr. Gupta
Keyword(s):  
Pathogenic Bacteria ◽  
Biological Activities ◽  
Aqueous Solubility ◽  
Gram Positive ◽  
Curcumin Nanoparticles ◽  
Superficial Skin ◽  
Potential Applications ◽  
Conventional Antibiotics

Gram-positive bacteria cause various diseases from the superficial skin to deep tissue infections. The capability of causing numerous diseases is due to the production of virulence factors which are tightly regulated by the virulence genes. Various Gram-positive pathogenic bacteria e.g. Staphylococcus, Mycobacterium, and Listeria are capable of causing lethal infections in humans and animals. Conventional antibiotics, targeted antibiotics, and combinatorial drugs are used as therapeutic agents against Gram-positive pathogens. Due to intricate virulence pathway bacteria readily adopt resistance to available drugs. Therefore, there is need to develop some alternative approaches to combat these infections. Various natural extracts are effective against pathogenic bacteria with or without the available drugs. Curcumin is a natural extract of Curcuma longas rhizome, known as turmeric. Curcumin shows various biological activities such as antimicrobial, antioxidant and anti-inflammatory. It also shows strong antibacterial activity against Gram-positive and few Gram-negative bacteria. Besides all these beneficial applications, major drawbacks of curcumin are poor aqueous solubility and less bioavailability. However, drug delivery approaches including nanoformulation are developed to increase its stability in vitro and in vivo settings. The present review article focused on the translation of potential applications of curcumin in various diseases specifically caused by Gram-positive pathogens. Various methods used for the formulations of curcumin nanoparticles, combinatorial strategies with curcumin nanoparticles and their application in the prevention of infections have been discussed. The present article also discusses the future aspects of curcumin-nanoparticles and its use as an alternative therapeutic approach against pathogens.

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