Pseudomonas aeruginosa is among the most dangerous Gram-negative opportunistic pathogens. In the compromised lung, P. aeruginosa is a common cause of ventilator-associated pneumonia, exacerbations in patients with chronic obstructive pulmonary disease, and chronic, lethal infections in individuals with the genetic disease cystic fibrosis. Both chronic and acute P. aeruginosa lung infections are difficult to treat and are associated with high rates of mortality, thus new strategies are needed to combat this bacterium. One important P. aeruginosa virulence factor is a secreted phospholipase C, PlcH, which degrades choline- containing phospholipids, such as phosphatidylcholine (PC), that are highly abundant in the lung. PlcH is cytotoxic, immunomodulatory and causes decreased lung function, and we have discovered a drug, already approved for use in humans, that inhibits PlcH activity, and prevents the effects of PlcH in an acute mouse pneumonia model. Our findings also indicate that P. aeruginosa PlcH-mediated degradation of host phopholipids provides the bacteria with precursors necessary to derive glycine betaine (GB). Through microarray studies, we have found that GB, in addition to being a nutrient and an osmoprotectant, also serves as a novel inducer of Anr, a central transcriptional regulator, in oxic environments where Anr is normally inactive. Our data show a novel role for Anr in biofilm formation and host cell colonization, and that GB stimulation of host colonization is Anr-dependent. Thus, our central hypothesis states that PlcH not only causes host damage, but also releases products that promote P. aeruginosa colonization of the host. Thus, inhibition of PlcH may decrease P. aeruginosa virulence directly and by decreasing antibiotic-resistant biofilms. In this proposal, we aim to test the hypothesis that GB directly increases Anr activity in oxic environments and determine the mechanism by which this occurs (Aim 1) and test the hypothesis that Anr promotes P. aeruginosa biofilm formation and host colonization by increasing the production of CupA fimbriae (Aim 2).
In Aim 2, we will also determine if Anr regulation of cupA gene expression is important for P. aeruginosa colonization of the mouse lung, and if there is evidence for GB synthesis, Anr activity, and cupA expression in acute and chronic P. aeruginosa infections in humans. Based on our preliminary data, we predict that the inhibition of PlcH by an existing drug will decrease P. aeruginosa GB levels, biofilm formation and antibiotic resistance, and we will test this hypothesis in Aim 3. Completion of these studies will unravel a new mechanism by which host-derived molecules impact virulence-related gene expression in P. aeruginosa, and may provide insight into the regulation of Anr homologs in other bacterial pathogens. We will pursue the novel and exciting possibility that the use of an exisitng drug that inhibits PlcH activity will both attenuate acute effects of PlcH on the lung and reduce airway colonization by P. aeruginosa rendering it more susceptible to existing antimicrobial therapies.

Public Health Relevance

Pseudomonas aeruginosa is one of the most common causes of hospital-acquired infections and a lethal pathogen of lungs of compromised patients and individuals with CF. Our studies indicate that an enzyme, PlcH, secreted by P. aeruginosa provides the bacterium with a host-derived molecule that serves a novel regulatory role in promoting host colonization. We have discovered a compound, already approved for use in humans, that inhibits PlcH activity in a mouse model, and we will determine if this therapy reduces P. aeruginosa levels in vivo and its resistance to existing antibiotic therapies.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Bacterial Pathogenesis Study Section (BACP)
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Taylor, Christopher E,
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Dartmouth College
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Chen, Kathleen M; Tan, Jie; Way, Gregory P et al. (2018) PathCORE-T: identifying and visualizing globally co-occurring pathways in large transcriptomic compendia. BioData Min 11:14
Limoli, Dominique H; Whitfield, Gregory B; Kitao, Tomoe et al. (2017) Pseudomonas aeruginosa Alginate Overproduction Promotes Coexistence with Staphylococcus aureus in a Model of Cystic Fibrosis Respiratory Infection. MBio 8:
Tan, Jie; Doing, Georgia; Lewis, Kimberley A et al. (2017) Unsupervised Extraction of Stable Expression Signatures from Public Compendia with an Ensemble of Neural Networks. Cell Syst 5:63-71.e6
Sakhtah, Hassan; Koyama, Leslie; Zhang, Yihan et al. (2016) The Pseudomonas aeruginosa efflux pump MexGHI-OpmD transports a natural phenazine that controls gene expression and biofilm development. Proc Natl Acad Sci U S A 113:E3538-47
Greene, Casey S; Foster, James A; Stanton, Bruce A et al. (2016) COMPUTATIONAL APPROACHES TO STUDY MICROBES AND MICROBIOMES. Pac Symp Biocomput 21:557-67
Koeppen, Katja; Hampton, Thomas H; Jarek, Michael et al. (2016) A Novel Mechanism of Host-Pathogen Interaction through sRNA in Bacterial Outer Membrane Vesicles. PLoS Pathog 12:e1005672
Tan, Jie; Hammond, John H; Hogan, Deborah A et al. (2016) ADAGE-Based Integration of Publicly Available Pseudomonas aeruginosa Gene Expression Data with Denoising Autoencoders Illuminates Microbe-Host Interactions. mSystems 1:
Hammond, John H; Hebert, Wesley P; Naimie, Amanda et al. (2016) Environmentally Endemic Pseudomonas aeruginosa Strains with Mutations in lasR Are Associated with Increased Disease Severity in Corneal Ulcers. mSphere 1:
Gifford, Alex H; Willger, Sven D; Dolben, Emily L et al. (2016) Use of a Multiplex Transcript Method for Analysis of Pseudomonas aeruginosa Gene Expression Profiles in the Cystic Fibrosis Lung. Infect Immun 84:2995-3006
McFarland, Kirsty A; Dolben, Emily L; LeRoux, Michele et al. (2015) A self-lysis pathway that enhances the virulence of a pathogenic bacterium. Proc Natl Acad Sci U S A 112:8433-8

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