Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 18 of 18
Full-Text Articles in Medicine and Health Sciences
The Pseudomonas Aeruginosa Efflux Pump Mexghi-Opmd Transports A Natural Phenazine That Controls Gene Expression And Biofilm Development, Hassan Sakhtah, Leslie Koyama, Yihan Zhang, Diana K. Morales, Blanche Fields, Alexa Price-Whelan, Deborah Hogan
The Pseudomonas Aeruginosa Efflux Pump Mexghi-Opmd Transports A Natural Phenazine That Controls Gene Expression And Biofilm Development, Hassan Sakhtah, Leslie Koyama, Yihan Zhang, Diana K. Morales, Blanche Fields, Alexa Price-Whelan, Deborah Hogan
Dartmouth Scholarship
Redox-cycling compounds, including endogenously produced phenazine antibiotics, induce expression of the efflux pump MexGHI-OpmD in the opportunistic pathogen Pseudomonas aeruginosa Previous studies of P. aeruginosa virulence, physiology, and biofilm development have focused on the blue phenazine pyocyanin and the yellow phenazine-1-carboxylic acid (PCA). In P. aeruginosa phenazine biosynthesis, conversion of PCA to pyocyanin is presumed to proceed through the intermediate 5-methylphenazine-1-carboxylate (5-Me-PCA), a reactive compound that has eluded detection in most laboratory samples. Here, we apply electrochemical methods to directly detect 5-Me-PCA and find that it is transported by MexGHI-OpmD in P. aeruginosa strain PA14 planktonic and biofilm cells. We …
A Self-Lysis Pathway That Enhances The Virulence Of A Pathogenic Bacterium, Kirsty A. Mcfarland, Emily L. Dolben, Michele Leroux, Tracy K. Kambara, Kathryn Ramsey, Robin Kirkpatrick, Joseph Mougous, Deborah Hogan, Simon Dove
A Self-Lysis Pathway That Enhances The Virulence Of A Pathogenic Bacterium, Kirsty A. Mcfarland, Emily L. Dolben, Michele Leroux, Tracy K. Kambara, Kathryn Ramsey, Robin Kirkpatrick, Joseph Mougous, Deborah Hogan, Simon Dove
Dartmouth Scholarship
In mammalian cells, programmed cell death (PCD) plays important roles in development, in the removal of damaged cells, and in fighting bacterial infections. Although widespread among multicellular organisms, there are relatively few documented instances of PCD in bacteria. Here we describe a potential PCD pathway in Pseudomonas aeruginosa that enhances the ability of the bacterium to cause disease in a lung infection model. Activation of the system can occur in a subset of cells in response to DNA damage through cleavage of an essential transcription regulator we call AlpR. Cleavage of AlpR triggers a cell lysis program through de-repression of …
Links Between Anr And Quorum Sensing In Pseudomonas Aeruginosa Biofilms, John H. Hammond, Emily F. Dolben, T. Jarrod Smith, Sabin Bhuju, Deborah Hogan
Links Between Anr And Quorum Sensing In Pseudomonas Aeruginosa Biofilms, John H. Hammond, Emily F. Dolben, T. Jarrod Smith, Sabin Bhuju, Deborah Hogan
Dartmouth Scholarship
In Pseudomonas aeruginosa, the transcription factor Anr controls the cellular response to low oxygen or anoxia. Anr activity is high in oxygen-limited environments, including biofilms and populations associated with chronic infections, and Anr is necessary for persistence in a model of pulmonary infection. In this study, we characterized the Anr regulon in biofilm-grown cells at 1% oxygen in the laboratory strain PAO1 and in a quorum sensing (QS)-deficient clinical isolate, J215. As expected, transcripts related to denitrification, arginine fermentation, high-affinity cytochrome oxidases, and CupA fimbriae were lower in the Δanr derivatives. In addition, we observed that transcripts associated with quorum …
Coculture Of Staphylococcus Aureus With Pseudomonas Aeruginosa Drives S. Aureus Towards Fermentative Metabolism And Reduced Viability In A Cystic Fibrosis Model, Laura M. Filkins, Jyoti A. Graber, Daniel G. Olson, Emily L. Dolben, Lee Lynd, Sabin Bhuju, George A. O'Toole
Coculture Of Staphylococcus Aureus With Pseudomonas Aeruginosa Drives S. Aureus Towards Fermentative Metabolism And Reduced Viability In A Cystic Fibrosis Model, Laura M. Filkins, Jyoti A. Graber, Daniel G. Olson, Emily L. Dolben, Lee Lynd, Sabin Bhuju, George A. O'Toole
Dartmouth Scholarship
The airways of patients with cystic fibrosis are colonized with diverse bacterial communities that change dynamically during pediatric years and early adulthood. Staphylococcus aureus is the most prevalent pathogen during early childhood, but during late teens and early adulthood, a shift in microbial composition occurs leading to Pseudomonas aeruginosa community predominance in ∼50% of adults. We developed a robust dual-bacterial in vitro coculture system of P. aeruginosa and S. aureus on monolayers of human bronchial epithelial cells homozygous for the ΔF508 cystic fibrosis transmembrane conductance regulator (CFTR) mutation to better model the mechanisms of this interaction. We show that P. …
Acidosis Potentiates The Host Proinflammatory Interleukin-1Β Response To Pseudomonas Aeruginosa Infection, I. M. Torres, Y. R. Patankar, Tamer B. Shabaneh, E. Dolben, Deborah Hogan, David Leib, Brent L. Berwin
Acidosis Potentiates The Host Proinflammatory Interleukin-1Β Response To Pseudomonas Aeruginosa Infection, I. M. Torres, Y. R. Patankar, Tamer B. Shabaneh, E. Dolben, Deborah Hogan, David Leib, Brent L. Berwin
Dartmouth Scholarship
Infection by Pseudomonas aeruginosa, and bacteria in general, frequently promotes acidification of the local microenvironment, and this is reinforced by pulmonary exertion and exacerbation. However, the consequence of an acidic environment on the host inflammatory response to P. aeruginosa infection is poorly understood. Here we report that the pivotal cellular and host proinflammatory interleukin-1β (IL-1β) response, which enables host clearance of the infection but can produce collateral inflammatory damage, is increased in response to P. aeruginosa infection within an acidic environment. Synergistic mechanisms that promote increased IL-1β release in response to P. aeruginosa infection in an acidic environment are …
Epoxide-Mediated Differential Packaging Of Cif And Other Virulence Factors Into Outer Membrane Vesicles, A. E. Ballok, L. M. Filkins, J.. M. Bomberger, B. A. Stanton, George A. O'Toole
Epoxide-Mediated Differential Packaging Of Cif And Other Virulence Factors Into Outer Membrane Vesicles, A. E. Ballok, L. M. Filkins, J.. M. Bomberger, B. A. Stanton, George A. O'Toole
Dartmouth Scholarship
Pseudomonas aeruginosa produces outer membrane vesicles (OMVs) that contain a number of secreted bacterial proteins, including phospholipases, alkaline phosphatase, and the CFTR inhibitory factor (Cif). Previously, Cif, an epoxide hydrolase, was shown to be regulated at the transcriptional level by epoxides, which serve as ligands of the repressor, CifR. Here, we tested whether epoxides have an effect on Cif levels in OMVs. We showed that growth of P. aeruginosa in the presence of specific epoxi
Pouring Salt On A Wound: Pseudomonas Aeruginosa Virulence Factors Alter Na+ And Cl− Flux In The Lung, Alicia E. Ballok, George A. O'Toole
Pouring Salt On A Wound: Pseudomonas Aeruginosa Virulence Factors Alter Na+ And Cl− Flux In The Lung, Alicia E. Ballok, George A. O'Toole
Dartmouth Scholarship
Pseudomonas aeruginosa is a ubiquitous opportunistic pathogen with multiple niches in the human body, including the lung. P. aeruginosa infections are particularly damaging or fatal for patients with ventilator-associated pneumonia, chronic obstructive pulmonary disease, and cystic fibrosis (CF). To establish an infection, P. aeruginosa relies on a suite of virulence factors, including lipopolysaccharide, phospholipases, exoproteases, phenazines, outer membrane vesicles, type III secreted effectors, flagella, and pili. These factors not only damage the epithelial cell lining but also induce changes in cell physiology and function such as cell shape, membrane permeability, and protein synthesis. While such virulence factors are important in …
Anr And Its Activation By Plch Activity In Pseudomonas Aeruginosa Host Colonization And Virulence, Angelyca A. Jackson, Maegan J. Gross, Emily F. Daniels, Thomas H. Hampton, John H. Hammond, Isabelle Vallet-Gely, Simon L. Dove, Bruce A. Stanton, Deborah A. Hogan
Anr And Its Activation By Plch Activity In Pseudomonas Aeruginosa Host Colonization And Virulence, Angelyca A. Jackson, Maegan J. Gross, Emily F. Daniels, Thomas H. Hampton, John H. Hammond, Isabelle Vallet-Gely, Simon L. Dove, Bruce A. Stanton, Deborah A. Hogan
Dartmouth Scholarship
Pseudomonas aeruginosa hemolytic phospholipase C (PlcH) degrades phosphatidylcholine (PC), an abundant lipid in cell membranes and lung surfactant. A ΔplcHR mutant, known to be defective in virulence in animal models, was less able to colonize epithelial cell monolayers and was defective in biofilm formation on plastic when grown in lung surfactant. Microarray analyses found that strains defective in PlcH production had lower levels of Anr-regulated transcripts than the wild type. PC degradation stimulated the Anr regulon in an Anr-dependent manner under conditions where Anr activity was submaximal because of the presence of oxygen. Two PC catabolites, choline and glycine …
Epoxide-Mediated Cifr Repression Of Cif Gene Expression Utilizes Two Binding Sites In Pseudomonas Aeruginosa, Alicia E. Ballok, Christopher D. Bahl, Emily L. Dolben, Allia K. Lindsay, Jessica D. St. Laurent, Deborah Hogan, Dean Madden, George A. O'Toole
Epoxide-Mediated Cifr Repression Of Cif Gene Expression Utilizes Two Binding Sites In Pseudomonas Aeruginosa, Alicia E. Ballok, Christopher D. Bahl, Emily L. Dolben, Allia K. Lindsay, Jessica D. St. Laurent, Deborah Hogan, Dean Madden, George A. O'Toole
Dartmouth Scholarship
Pseudomonas aeruginosa secretes an epoxide hydrolase virulence factor that reduces the apical membrane expression of ABC transporters such as the cystic fibrosis transmembrane conductance regulator (CFTR). This virulence factor, named CFTR inhibitory factor (Cif), is regulated by a TetR-family, epoxide-responsive repressor known as CifR via direct binding and repression. We identified two sites of CifR binding in the intergenic space between cifR and morB, the first gene in the operon containing the cif gene. We have mapped these binding sites and found they are 27 bp in length, and they overlap the -10 and +1 sites of both the cifR …
The Pseudomonas Aeruginosa Magnesium Transporter Mgte Inhibits Transcription Of The Type Iii Secretion System, Gregory G. Anderson, Timothy L. Yahr, Rustin R. Lovewell, George A. O'Toole
The Pseudomonas Aeruginosa Magnesium Transporter Mgte Inhibits Transcription Of The Type Iii Secretion System, Gregory G. Anderson, Timothy L. Yahr, Rustin R. Lovewell, George A. O'Toole
Dartmouth Scholarship
Pseudomonas aeruginosa is an opportunistic pathogen that causes life-long pneumonia in individuals with cystic fibrosis (CF). These long-term infections are maintained by bacterial biofilm formation in the CF lung. We have recently developed a model of P. aeruginosa biofilm formation on cultured CF airway epithelial cells. Using this model, we discovered that mutation of a putative magnesium transporter gene, called mgtE, led to increased cytotoxicity of P. aeruginosa toward epithelial cells. This altered toxicity appeared to be dependent upon expression of the type III secretion system (T3SS). In this study, we found that mutation of mgtE results in increased T3SS …
Pseudomonas Aeruginosa Evasion Of Phagocytosis Is Mediated By Loss Of Swimming Motility And Is Independent Of Flagellum Expression, Eyal Amiel, Rustin R. Lovewell, George A. O'Toole, Deborah A. Hogan, Brent Berwin
Pseudomonas Aeruginosa Evasion Of Phagocytosis Is Mediated By Loss Of Swimming Motility And Is Independent Of Flagellum Expression, Eyal Amiel, Rustin R. Lovewell, George A. O'Toole, Deborah A. Hogan, Brent Berwin
Dartmouth Scholarship
Pseudomonas aeruginosa is a pathogenic Gram-negative bacterium that causes severe opportunistic infections in immunocompromised individuals; in particular, severity of infection with P. aeruginosa positively correlates with poor prognosis in cystic fibrosis (CF) patients. Establishment of chronic infection by this pathogen is associated with downregulation of flagellar expression and of other genes that regulate P. aeruginosa motility. The current paradigm is that loss of flagellar expression enables immune evasion by the bacteria due to loss of engagement by phagocytic receptors that recognize flagellar components and loss of immune activation through flagellin-mediated Toll-like receptor (TLR) signaling. In this work, we employ bacterial …
Gbdr Regulates Pseudomonas Aeruginosa Plch And Pchp Transcription In Response To Choline Catabolites, Matthew J. Wargo, Tiffany C. Ho, Maegan J. Gross, Laurie A. Whittaker, Deborah A. Hogan
Gbdr Regulates Pseudomonas Aeruginosa Plch And Pchp Transcription In Response To Choline Catabolites, Matthew J. Wargo, Tiffany C. Ho, Maegan J. Gross, Laurie A. Whittaker, Deborah A. Hogan
Dartmouth Scholarship
Pseudomonas aeruginosa hemolytic phospholipase C, PlcH, can degrade phosphatidylcholine (PC) and sphingomyelin in eukaryotic cell membranes and extracellular PC in lung surfactant. Numerous studies implicate PlcH in P. aeruginosa virulence. The phosphorylcholine released by PlcH activity on phospholipids is hydrolyzed by a periplasmic phosphorylcholine phosphatase, PchP. Both plcH gene expression and PchP enzyme activity are positively regulated by phosphorylcholine degradation products, including glycine betaine. Here we report that the induction of plcH and pchP transcription by glycine betaine is mediated by GbdR, an AraC family transcription factor. Mutants that lack gbdR are unable to induce plcH and pchP in media …
Flagellum-Mediated Biofilm Defense Mechanisms Of Pseudomonas Aeruginosa Against Host-Derived Lactoferrin, Jeff G. Leid, Mathias Kerr, Candice Selgado, Chelsa Johnson, Gabriel Moreno, Alyssa Smith, Mark E. Shirtliff, Georg A. O'Toole, Emily K. Cope
Flagellum-Mediated Biofilm Defense Mechanisms Of Pseudomonas Aeruginosa Against Host-Derived Lactoferrin, Jeff G. Leid, Mathias Kerr, Candice Selgado, Chelsa Johnson, Gabriel Moreno, Alyssa Smith, Mark E. Shirtliff, Georg A. O'Toole, Emily K. Cope
Dartmouth Scholarship
Chronic infection with the gram-negative organism Pseudomonas aeruginosa is a leading cause of morbidity and mortality in human patients, despite high doses of antibiotics used to treat the various diseases this organism causes. These infections are chronic because P. aeruginosa readily forms biofilms, which are inherently resistant to antibiotics as well as the host's immune system. Our laboratory has been investigating specific mutations in P. aeruginosa that regulate biofilm bacterial susceptibility to the host. To continue our investigation of the role of genetics in bacterial biofilm host resistance, we examined P. aeruginosa biofilms that lack the flgK gene. This mutant …
Long-Distance Delivery Of Bacterial Virulence Factors By Pseudomonas Aeruginosa Outer Membrane Vesicles, Jennifer M. Bomberger, Daniel P. Maceachran, Bonita A. Coutermarsh, Siying Ye, George A. O'Toole, Bruce A. Stanton, Frederick M. Ausubel
Long-Distance Delivery Of Bacterial Virulence Factors By Pseudomonas Aeruginosa Outer Membrane Vesicles, Jennifer M. Bomberger, Daniel P. Maceachran, Bonita A. Coutermarsh, Siying Ye, George A. O'Toole, Bruce A. Stanton, Frederick M. Ausubel
Dartmouth Scholarship
Bacteria use a variety of secreted virulence factors to manipulate host cells, thereby causing significant morbidity and mortality. We report a mechanism for the long-distance delivery of multiple bacterial virulence factors, simultaneously and directly into the host cell cytoplasm, thus obviating the need for direct interaction of the pathogen with the host cell to cause cytotoxicity. We show that outer membrane–derived vesicles (OMV) secreted by the opportunistic human pathogen Pseudomonas aeruginosa deliver multiple virulence factors, including β-lactamase, alkaline phosphatase, hemolytic phospholipase C, and Cif, directly into the host cytoplasm via fusion of OMV with lipid rafts in the host plasma …
Cif Is Negatively Regulated By The Tetr Family Repressor Cifr, Daniel P. Maceachran, Bruce A. Stanton, George A. O'Toole
Cif Is Negatively Regulated By The Tetr Family Repressor Cifr, Daniel P. Maceachran, Bruce A. Stanton, George A. O'Toole
Dartmouth Scholarship
We previously reported that the novel Pseudomonas aeruginosa toxin Cif is capable of decreasing apical membrane expression of the cystic fibrosis transmembrane conductance regulator (CFTR). We further demonstrated that Cif is capable of degrading the synthetic epoxide hydrolase (EH) substrate S-NEPC [(2S,3S)-trans-3-phenyl-2-oxiranylmethyl 4-nitrophenol carbonate], suggesting that Cif may be reducing apical membrane expression of CFTR via its EH activity. Here we report that Cif is capable of degrading the xenobiotic epoxide epibromohydrin (EBH) to its vicinal diol 3-bromo-1,2-propanediol. We also demonstrate that this epoxide is a potent inducer of cif gene expression. We show that the predicted TetR family transcriptional …
In Vitro Analysis Of Tobramycin-Treated Pseudomonas Aeruginosa Biofilms On Cystic Fibrosis-Derived Airway Epithelial Cells, Gregory G. Anderson, Sophie Moreau-Marquis, Bruce A. Stanton, George A. O'Toole
In Vitro Analysis Of Tobramycin-Treated Pseudomonas Aeruginosa Biofilms On Cystic Fibrosis-Derived Airway Epithelial Cells, Gregory G. Anderson, Sophie Moreau-Marquis, Bruce A. Stanton, George A. O'Toole
Dartmouth Scholarship
P. aeruginosa forms biofilms in the lungs of individuals with cystic fibrosis (CF); however, there have been no effective model systems for studying biofilm formation in the CF lung. We have developed a tissue culture system for growth of P. aeruginosa biofilms on CF-derived human airway cells that promotes the formation of highly antibiotic-resistant microcolonies, which produce an extracellular polysaccharide matrix and require the known abiotic biofilm formation genes flgK and pilB. Treatment of P. aeruginosa biofilms with tobramycin reduced the virulence of the biofilms both by reducing bacterial numbers and by altering virulence gene expression. We performed microarray analysis …
The Flagellum Of Pseudomonas Aeruginosa Is Required For Resistance To Clearance By Surfactant Protein A, Shiping Zhang, Francis X. Mccormack, Roger C. Levesque, George A. O'Toole, Gee W. Lau
The Flagellum Of Pseudomonas Aeruginosa Is Required For Resistance To Clearance By Surfactant Protein A, Shiping Zhang, Francis X. Mccormack, Roger C. Levesque, George A. O'Toole, Gee W. Lau
Dartmouth Scholarship
Surfactant protein A (SP-A) is an important lung innate immune protein that kills microbial pathogens by opsonization and membrane permeabilization. We investigated the basis of SP-A-mediated pulmonary clearance of Pseudomonas aeruginosa using genetically-engineered SP-A mice and a library of signature-tagged P. aeruginosa mutants. A mutant with an insertion into flgE, the gene that encodes flagellar hook protein, was preferentially cleared by the SP-A(+/+) mice, but survived in the SP-A(-/-) mice. Opsonization by SP-A did not play a role in flgE clearance. However, exposure to SP-A directly permeabilized and killed the flgE mutant, but not the wild-type parental strain. P. aeruginosa …
Alginate Is Not A Significant Component Of The Extracellular Polysaccharide Matrix Of Pa14 And Pao1 Pseudomonas Aeruginosa Biofilms, Daniel J. Wozniak, Timna J. O. Wyckoff, Melissa Starkey, Rebecca Keyser, Parastoo Azadi, George A. O'Toole, Matthew R. Parsek
Alginate Is Not A Significant Component Of The Extracellular Polysaccharide Matrix Of Pa14 And Pao1 Pseudomonas Aeruginosa Biofilms, Daniel J. Wozniak, Timna J. O. Wyckoff, Melissa Starkey, Rebecca Keyser, Parastoo Azadi, George A. O'Toole, Matthew R. Parsek
Dartmouth Scholarship
The bacterium Pseudomonas aeruginosa causes chronic respiratory infections in cystic fibrosis (CF) patients. Such infections are extremely difficult to control because the bacteria exhibit a biofilm-mode of growth, rendering P. aeruginosa resistant to antibiotics and phagocytic cells. During the course of infection, P. aeruginosa usually undergoes a phenotypic switch to a mucoid colony, which is characterized by the overproduction of the exopolysaccharide alginate. Alginate overproduction has been implicated in protecting P. aeruginosa from the harsh environment present in the CF lung, as well as facilitating its persistence as a biofilm by providing an extracellular matrix that promotes adherence. Because of …