scholarly journals Bistable Expression of CsgD in Salmonella enterica Serovar Typhimurium Connects Virulence to Persistence

2015 ◽  
Vol 83 (6) ◽  
pp. 2312-2326 ◽  
Author(s):  
Keith D. MacKenzie ◽  
Yejun Wang ◽  
Dylan J. Shivak ◽  
Cynthia S. Wong ◽  
Leia J. L. Hoffman ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Pathogenic Bacteria ◽  
Single Cells ◽  
Smooth Transition ◽  
Intestinal Cell ◽  
Planktonic Cells ◽  
Multicellular Aggregate ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Cell Subpopulations

Pathogenic bacteria often need to survive in the host and the environment, and it is not well understood how cells transition between these equally challenging situations. For the human and animal pathogenSalmonella entericaserovar Typhimurium, biofilm formation is correlated with persistence outside a host, but the connection to virulence is unknown. In this study, we analyzed multicellular-aggregate and planktonic-cell subpopulations that coexist whenS. Typhimurium is grown under biofilm-inducing conditions. These cell types arise due to bistable expression of CsgD, the central biofilm regulator. Despite being exposed to the same stresses, the two cell subpopulations had 1,856 genes that were differentially expressed, as determined by transcriptome sequencing (RNA-seq). Aggregated cells displayed the characteristic gene expression of biofilms, whereas planktonic cells had enhanced expression of numerous virulence genes. Increased type three secretion synthesis in planktonic cells correlated with enhanced invasion of a human intestinal cell line and significantly increased virulence in mice compared to the aggregates. However, when the same groups of cells were exposed to desiccation, the aggregates survived better, and the competitive advantage of planktonic cells was lost. We hypothesize that CsgD-based differentiation is a form of bet hedging, with single cells primed for host cell invasion and aggregated cells adapted for persistence in the environment. This allowsS. Typhimurium to spread the risks of transmission and ensures a smooth transition between the host and the environment.

scholarly journals Quinazoline-Based Antivirulence Compounds Selectively Target Salmonella PhoP/PhoQ Signal Transduction System

2019 ◽  
Vol 64 (1) ◽  
Author(s):  
María Ayelén Carabajal ◽  
Christopher R. M. Asquith ◽  
Tuomo Laitinen ◽  
Graham J. Tizzard ◽  
Lucía Yim ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Salmonella Enterica ◽  
Pathogenic Bacteria ◽  
Catalytic Domain ◽  
Kinase Inhibitor ◽  
Adaptive Responses ◽  
Antibacterial Compounds ◽  
Content Type ◽  
Two Component ◽  
Serovar Typhimurium

ABSTRACT The rapid emergence of multidrug resistance among bacterial pathogens has become a significant challenge to human health in our century. Therefore, development of next-generation antibacterial compounds is an urgent need. Two-component signal transduction systems (TCS) are stimulus-response coupling devices that allow bacteria to sense and elaborate adaptive responses to changing environmental conditions, including the challenges that pathogenic bacteria face inside the host. The differential presence of TCS, present in bacteria but absent in the animal kingdom, makes them attractive targets in the search for new antibacterial compounds. In Salmonella enterica, the PhoP/PhoQ two-component system controls the expression of crucial phenotypes that define the ability of the pathogen to establish infection in the host. We now report the screening of 686 compounds from a GlaxoSmithKline published kinase inhibitor set in a high-throughput whole-cell assay that targets Salmonella enterica serovar Typhimurium PhoP/PhoQ. We identified a series of quinazoline compounds that showed selective and potent downregulation of PhoP/PhoQ-activated genes and define structural attributes required for their efficacy. We demonstrate that their bioactivity is due to repression of the PhoQ sensor autokinase activity mediated by interaction with its catalytic domain, acting as competitive inhibitors of ATP binding. While noncytotoxic, the hit molecules exhibit antivirulence effect by blockage of S. Typhimurium intramacrophage replication. Together, these features make these quinazoline compounds stand out as exciting leads to develop a therapeutic intervention to fight salmonellosis.

scholarly journals Hydrosol of Thymbra capitata Is a Highly Efficient Biocide against Salmonella enterica Serovar Typhimurium Biofilms

2016 ◽  
Vol 82 (17) ◽  
pp. 5309-5319 ◽  
Author(s):  
Foteini Karampoula ◽  
Efstathios Giaouris ◽  
Julien Deschamps ◽  
Agapi I. Doulgeraki ◽  
George-John E. Nychas ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Laser Scanning ◽  
High Efficiency ◽  
3D Structure ◽  
Time Lapse ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Planktonic Cells ◽  
Content Type ◽  
Serovar Typhimurium

ABSTRACTSalmonellais recognized as one of the most significant enteric foodborne bacterial pathogens. In recent years, the resistance of pathogens to biocides and other environmental stresses, especially when they are embedded in biofilm structures, has led to the search for and development of novel antimicrobial strategies capable of displaying both high efficiency and safety. In this direction, the aims of the present work were to evaluate the antimicrobial activity of hydrosol of the Mediterranean spiceThymbracapitataagainst both planktonic and biofilm cells ofSalmonella entericaserovar Typhimurium and to compare its action with that of benzalkonium chloride (BC), a commonly used industrial biocide. In order to achieve this, the disinfectant activity following 6-min treatments was comparatively evaluated for both disinfectants by calculating the concentrations needed to achieve the same log reductions against both types of cells. Their bactericidal effect against biofilm cells was also comparatively determined byin situand real-time visualization of cell inactivation through the use of time-lapse confocal laser scanning microscopy (CLSM). Interestingly, results revealed that hydrosol was almost equally effective against biofilms and planktonic cells, whereas a 200-times-higher concentration of BC was needed to achieve the same effect against biofilm compared to planktonic cells. Similarly, time-lapse CLSM revealed the significant advantage of the hydrosol to easily penetrate within the biofilm structure and quickly kill the cells, despite the three-dimensional (3D) structure ofSalmonellabiofilm.IMPORTANCEThe results of this paper highlight the significant antimicrobial action of a natural compound, hydrosol ofThymbra capitata, against both planktonic and biofilm cells of a common foodborne pathogen. Hydrosol has numerous advantages as a disinfectant of food-contact surfaces. It is an aqueous solution which can easily be rinsed out from surfaces, it does not have the strong smell of the essential oil (EO) and it is a byproduct of the EO distillation procedure without any industrial application until now. Consequently, hydrosol obviously could be of great value to combat biofilms and thus to improve product safety not only for the food industries but probably also for many other industries which experience biofilm-related problems.

scholarly journals Mapping and Regulation of Genes within Salmonella Pathogenicity Island 12 That Contribute toIn VivoFitness of Salmonella enterica Serovar Typhimurium

2013 ◽  
Vol 81 (7) ◽  
pp. 2394-2404 ◽  
Author(s):  
Ana M. Tomljenovic-Berube ◽  
Brandyn Henriksbo ◽  
Steffen Porwollik ◽  
Colin A. Cooper ◽  
Brian R. Tuinema ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Salmonella Enterica ◽  
Pathogenic Bacteria ◽  
Pathogenicity Island ◽  
Bacterial Survival ◽  
Content Type ◽  
Reverse Transcription Pcr ◽  
Serovar Typhimurium ◽  
Bacterial Fitness ◽  
Virulence Regulator

ABSTRACTSalmonellapathogenicity island 12 (SPI-12) ofSalmonella entericaserovar Typhimurium is a 15-kb region that encompasses genesSTM2230toSTM2245and encodes a remnant phage known to contribute to bacterial virulence. In mouse infection experiments and replication assays in macrophages, we demonstrated a role for four genes in SPI-12 for bacterial survival in the host. STM2239, a potential Q antiterminator, showed a prominent contribution to bacterial fitness. Transcriptional reporter experiments, quantitative reverse transcription-PCR (RT-PCR), and immunoblotting demonstrated that the virulence regulator SsrB and STM2239 contribute to transcriptional activation of genes in SPI-12. SsrB was found to indirectly regulate this locus by transcriptional read-through from thesspH2(STM2241) promoter. Chromatin immunoprecipitation showed that STM2239 copurified with the promoter regulatingSTM2237, suggesting that STM2239 may function as an antiterminator to activate adjacent genes. These results demonstrate that bacteriophage genes may be adapted by pathogenic bacteria to improve fitness in the host.

scholarly journals Efficiency of Conditionally Attenuated Salmonella enterica Serovar Typhimurium in Bacterium-Mediated Tumor Therapy

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Michael Frahm ◽  
Sebastian Felgner ◽  
Dino Kocijancic ◽  
Manfred Rohde ◽  
Michael Hensel ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Tumor Targeting ◽  
Antitumor Effect ◽  
Treatment Options ◽  
Tumor Therapy ◽  
Therapeutic Benefit ◽  
Industrialized Countries ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Therapeutic Molecules

ABSTRACTIncreasing numbers of cancer cases generate a great urge for new treatment options. Applying bacteria likeSalmonella entericaserovar Typhimurium for cancer therapy represents an intensively explored option. These bacteria have been shown not only to colonize solid tumors but also to exhibit an intrinsic antitumor effect. In addition, they could serve as tumor-targeting vectors for therapeutic molecules. However, the pathogenicS. Typhimurium strains used for tumor therapy need to be attenuated for safe application. Here, lipopolysaccharide (LPS) deletion mutants (ΔrfaL, ΔrfaG, ΔrfaH, ΔrfaD, ΔrfaP, and ΔmsbBmutants) ofSalmonellawere investigated for efficiency in tumor therapy. Of such variants, the ΔrfaDand ΔrfaGdeep rough mutants exhibited the best tumor specificity and lowest pathogenicity. However, the intrinsic antitumor effect was found to be weak. To overcome this limitation, conditional attenuation was tested by complementing the mutants with an inducible arabinose promoter. The chromosomal integration of the respective LPS biosynthesis genes into thearaBADlocus exhibited the best balance of attenuation and therapeutic benefit. Thus, the present study establishes a basis for the development of an applicably cancer therapeutic bacterium.IMPORTANCECancer has become the second most frequent cause of death in industrialized countries. This and the drawbacks of routine therapies generate an urgent need for novel treatment options. Applying appropriately modifiedS. Typhimurium for therapy represents the major challenge of bacterium-mediated tumor therapy. In the present study, we demonstrated thatSalmonellabacteria conditionally modified in their LPS phenotype exhibit a safe tumor-targeting phenotype. Moreover, they could represent a suitable vehicle to shuttle therapeutic compounds directly into cancerous tissue without harming the host.

scholarly journals Whole-Genome Sequence of Salmonella enterica subsp. enterica Serovar Typhimurium Strain UPM 260, Isolated from a Broiler Chicken in Perak, Malaysia

2017 ◽  
Vol 5 (46) ◽  
Author(s):  
Najwa Syahirah Roslan ◽  
Shagufta Jabeen ◽  
Nurulfiza Mat Isa ◽  
Abdul Rahman Omar ◽  
Mohd Hair Bejo ◽  
...  
Keyword(s):  
Genome Sequence ◽  
Salmonella Enterica ◽  
Broiler Chicken ◽  
Whole Genome Sequence ◽  
Whole Genome ◽  
Content Type ◽  
Typhimurium Strain ◽  
Serovar Typhimurium

ABSTRACT Salmonella enterica subsp. enterica serovar Typhimurium is one of several well-categorized Salmonella serotypes recognized globally. Here, we report the whole-genome sequence of S. Typhimurium strain UPM 260, isolated from a broiler chicken.

scholarly journals Association of a Protective Monoclonal IgA with the O Antigen of Salmonella enterica Serovar Typhimurium Impacts Type 3 Secretion and Outer Membrane Integrity

2012 ◽  
Vol 80 (7) ◽  
pp. 2454-2463 ◽  
Author(s):  
Stephen J. Forbes ◽  
Daniel Martinelli ◽  
Chyongere Hsieh ◽  
Jeffrey G. Ault ◽  
Michael Marko ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Outer Membrane ◽  
Salmonella Enterica ◽  
Membrane Integrity ◽  
Effector Proteins ◽  
Content Type ◽  
O Antigen ◽  
Serovar Typhimurium ◽  
Type 3

ABSTRACTInvasion of intestinal epithelial cells bySalmonella entericaserovar Typhimurium is an energetically demanding process, involving the transfer of effector proteins from invading bacteria into host cells via a specialized organelle known as theSalmonellapathogenicity island 1 (SPI-1) type 3 secretion system (T3SS). By a mechanism that remains poorly understood, entry ofS. Typhimurium into epithelial cells is inhibited by Sal4, a monoclonal, polymeric IgA antibody that binds an immunodominant epitope within the O-antigen (O-Ag) component of lipopolysaccharide. In this study, we investigated how the binding of Sal4 to the surface ofS. Typhimurium influences T3SS activity, bacterial energetics, and outer membrane integrity. We found that Sal4 treatment impaired T3SS-mediated translocon formation and attenuated the delivery of tagged effector proteins into epithelial cells. Sal4 treatment coincided with a partial reduction in membrane energetics and intracellular ATP levels, possibly explaining the impairment in T3SS activity. Sal4's effects on bacterial secretion and energetics occurred concurrently with an increase in O-Ag levels in culture supernatants, alterations in outer membrane permeability, and changes in surface ultrastructure, as revealed by transmission electron microscopy and cryo-electron microscopy. We propose that Sal4, by virtue of its ability to bind and cross-link the O-Ag, induces a form of outer membrane stress that compromises the integrity of theS. Typhimurium cell envelope and temporarily renders the bacterium avirulent.

scholarly journals Draft Genome Sequence of Lactobacillus fermentum Lf2, an Exopolysaccharide-Producing Strain Isolated from Argentine Cheese

2018 ◽  
Vol 7 (18) ◽  
Author(s):  
Hugh M. B. Harris ◽  
Elisa C. Ale ◽  
Jorge A. Reinheimer ◽  
Ana G. Binetti ◽  
Paul W. O’Toole
Keyword(s):  
Genome Sequence ◽  
Salmonella Enterica ◽  
Draft Genome ◽  
Protective Role ◽  
Lactobacillus Fermentum ◽  
Draft Genome Sequence ◽  
Content Type ◽  
Serovar Typhimurium ◽  
High Concentrations

Lactobacillus fermentum Lf2, an Argentine cheese isolate, can produce high concentrations of exopolysaccharides (EPS). These EPS were shown to improve the texture and rheology of yogurt, as well as to play a protective role in mice exposed to Salmonella enterica serovar Typhimurium.

scholarly journals Regulation of RamA by RamR in Salmonella enterica Serovar Typhimurium: Isolation of a RamR Superrepressor

2012 ◽  
Vol 56 (11) ◽  
pp. 6037-6040 ◽  
Author(s):  
Vito Ricci ◽  
Stephen J. W. Busby ◽  
Laura J. V. Piddock
Keyword(s):  
Transcription Factor ◽  
Salmonella Enterica ◽  
Fluorescent Protein ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Promoter Sequence ◽  
Palindromic Sequence ◽  
Content Type ◽  
Gfp Reporter ◽  
Serovar Typhimurium ◽  
Green Fluorescent

ABSTRACTRamA is a transcription factor involved in regulating multidrug resistance inSalmonella entericaserovar Typhimurium SL1344. Green fluorescent protein (GFP) reporter fusions were exploited to investigate the regulation of RamA expression by RamR. We show that RamR represses theramApromoter by binding to a palindromic sequence and describe a superrepressor RamR mutant that binds to theramApromoter sequence more efficiently, thus exhibiting aramAinactivated phenotype.

scholarly journals Curcumin Reduces the Motility of Salmonella enterica Serovar Typhimurium by Binding to the Flagella, Thereby Leading to Flagellar Fragility and Shedding

2016 ◽  
Vol 198 (13) ◽  
pp. 1798-1811 ◽  
Author(s):  
Sandhya Amol Marathe ◽  
Arjun Balakrishnan ◽  
Vidya Devi Negi ◽  
Deepika Sakorey ◽  
Nagasuma Chandra ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Binding Assay ◽  
Protein A ◽  
Intestinal Barrier ◽  
Site Directed Mutagenesis ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Flagellar Filament ◽  
Fluorescence Binding ◽  
Fluorescence Binding Assay

ABSTRACTOne of the important virulence properties of the pathogen is its ability to travel to a favorable environment, cross the viscous mucus barrier (intestinal barrier for enteric pathogens), and reach the epithelia to initiate pathogenesis with the help of an appendage, like flagella. Nonetheless, flagella can act as an “Achilles heel,” revealing the pathogen's presence to the host through the stimulation of innate and adaptive immune responses. We assessed whether curcumin, a dietary polyphenol, could alter the motility ofSalmonella, a foodborne pathogen. It reduced the motility ofSalmonella entericaserovar Typhimurium by shortening the length of the flagellar filament (from ∼8 μm to ∼5 μm) and decreasing its density (4 or 5 flagella/bacterium instead of 8 or 9 flagella/bacterium). Upon curcumin treatment, the percentage of flagellated bacteria declined from ∼84% to 59%. However, no change was detected in the expression of the flagellin gene and protein. A fluorescence binding assay demonstrated binding of curcumin to the flagellar filament. This might make the filament fragile, breaking it into smaller fragments. Computational analysis predicted the binding of curcumin, its analogues, and its degraded products to a flagellin molecule at an interface between domains D1 and D2. Site-directed mutagenesis and a fluorescence binding assay confirmed the binding of curcumin to flagellin at residues ASN120, ASP123, ASN163, SER164, ASN173, and GLN175.IMPORTANCEThis work, to our knowledge the first report of its kind, examines how curcumin targets flagellar density and affects the pathogenesis of bacteria. We found that curcumin does not affect any of the flagellar synthesis genes. Instead, it binds to the flagellum and makes it fragile. It increases the torsional stress on the flagellar filament that then breaks, leaving fewer flagella around the bacteria. Flagella, which are crucial ligands for Toll-like receptor 5, are some of the most important appendages ofSalmonella. Curcumin is an important component of turmeric, which is a major spice used in Asian cooking. The loss of flagella can, in turn, change the pathogenesis of bacteria, making them more robust and fit in the host.

scholarly journals Role of sapA and yfgA in Susceptibility to Antibody-Mediated Complement-Dependent Killing and Virulence of Salmonella enterica Serovar Typhimurium

2017 ◽  
Vol 85 (9) ◽  
Author(s):  
Edna M. Ondari ◽  
Jennifer N. Heath ◽  
Elizabeth J. Klemm ◽  
Gemma Langridge ◽  
Lars Barquist ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Protein Translocation ◽  
Invasive Disease ◽  
Immune Serum ◽  
Insertion Mutant ◽  
Content Type ◽  
Serovar Typhimurium ◽  
Serum Killing ◽  
Increased Sensitivity

ABSTRACT The ST313 pathovar of Salmonella enterica serovar Typhimurium contributes to a high burden of invasive disease among African infants and HIV-infected adults. It is characterized by genome degradation (loss of coding capacity) and has increased resistance to antibody-dependent complement-mediated killing compared with enterocolitis-causing strains of S. Typhimurium. Vaccination is an attractive disease-prevention strategy, and leading candidates focus on the induction of bactericidal antibodies. Antibody-resistant strains arising through further gene deletion could compromise such a strategy. Exposing a saturating transposon insertion mutant library of S. Typhimurium to immune serum identified a repertoire of S. Typhimurium genes that, when interrupted, result in increased resistance to serum killing. These genes included several involved in bacterial envelope biogenesis, protein translocation, and metabolism. We generated defined mutant derivatives using S. Typhimurium SL1344 as the host. Based on their initial levels of enhanced resistance to killing, yfgA and sapA mutants were selected for further characterization. The S. Typhimurium yfgA mutant lost the characteristic Salmonella rod-shaped appearance, exhibited increased sensitivity to osmotic and detergent stress, lacked very long lipopolysaccharide, was unable to invade enterocytes, and demonstrated decreased ability to infect mice. In contrast, the S. Typhimurium sapA mutants had similar sensitivity to osmotic and detergent stress and lipopolysaccharide profile and an increased ability to infect enterocytes compared with the wild type, but it had no increased ability to cause in vivo infection. These findings indicate that increased resistance to antibody-dependent complement-mediated killing secondary to genetic deletion is not necessarily accompanied by increased virulence and suggest the presence of different mechanisms of antibody resistance.

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