Many VA patients are susceptible and succumb to infections with the opportunistic pathogen, Pseudomonas aeruginosa. This can occur as a complication of emphysema, chronic bronchitis, cancer and immunosuppressive drug therapy. Exposure to this ubiquitous bacterium can result in nosocomial infections, which are common via respiratory ventilators, catheters, lumbar punctures and general surgery. P. aeruginosa is highly tolerant or resistant to most antibiotics, making it difficult to control such infections, which leads to a high mortality rate. The goal of tis research is to improve our understanding of the biosynthesis of a protective capsule-like polysaccharide called alginate, which is produced as a virulence factor by P. aeruginosa. During chronic respiratory infections (e.g., COPD), adaptive mutations occur in vivo that lead to the over production of this exopolysaccharide, which confers resistance to phagocytic killing. Such clinical isolates demonstrate mucoid colony morphology. Improving our understanding of this pathogenic mechanism in P. aeruginosa will enhance the management of pulmonary disease caused by this bacterium. Most of the enzymes for the production of alginate are clustered in an operon of 12 genes. In this study, we will: (1) Determine the role of the second messenger cyclic di-GMP in the polymerization of alginate, (2) Characterize the role of the membrane fusion protein (MFP) domain in Alg44, and (3) Characterize the protein-protein interactions among the alginate secretion proteins. In addition, as part of a drug discovery plan, we will (4) screen smal compound libraries for those that antagonize the acetylation of alginate, which is required for resistance to phagocytosis. In collaboration with a structural biologist, we will determine the structures of all the alginate biosynthetic proteins, which will lead to the analysis of site-direced mutants to better understand the polymerization-secretion complex. The long-term goal of this research is to understand the functions of all of the components required for the biosynthesis of alginate, which is now recognized as a critical virulence factor during pulmonary infection. The information gained could be vital for the development of new therapeutic approaches in the treatment of P. aeruginosa infections. The results of these studies will also contribute to our overall understanding of bacterial capsule biosynthesis, which is a common mechanism of bacterial virulence for avoiding the host immune response.

Public Health Relevance

Infection with the bacterium Pseudomonas aeruginosa is a significant problem among our veterans. Many VAMC patients are susceptible to opportunistic infections with P. aeruginosa due to complications with emphysema, chronic bronchitis, COPD and other disorders. Nosocomial infection during treatment with respiratory ventilators is also common. A key virulence factor of P. aeruginosa during pulmonary infection is the production of a capsule-like exopolysaccharide called alginate. A better understanding of the complex mechanisms involved in alginate biosynthesis could lead to novel therapies. This work is also of importance to the VA health system because Pseudomonas infections are very difficult to treat due to its innate antibiotic resistance.

National Institute of Health (NIH)
Veterans Affairs (VA)
Non-HHS Research Projects (I01)
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Infectious Diseases B (INFB)
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VA Veterans Administration Hospital
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Silo-Suh, Laura A; Suh, Sang-Jin; Ohman, Dennis E et al. (2015) Complete Genome Sequence of Pseudomonas aeruginosa Mucoid Strain FRD1, Isolated from a Cystic Fibrosis Patient. Genome Announc 3:
Whitney, John C; Whitfield, Gregory B; Marmont, Lindsey S et al. (2015) Dimeric c-di-GMP is required for post-translational regulation of alginate production in Pseudomonas aeruginosa. J Biol Chem 290:12451-62
Wood, Lynn F; Ohman, Dennis E (2015) Cell wall stress activates expression of a novel stress response facilitator (SrfA) under ?22 (AlgT/U) control in Pseudomonas aeruginosa. Microbiology 161:30-40
Riley, Laura M; Weadge, Joel T; Baker, Perrin et al. (2013) Structural and functional characterization of Pseudomonas aeruginosa AlgX: role of AlgX in alginate acetylation. J Biol Chem 288:22299-314
Wood, Lynn F; Ohman, Dennis E (2012) Identification of genes in the ?²² regulon of Pseudomonas aeruginosa required for cell envelope homeostasis in either the planktonic or the sessile mode of growth. MBio 3:
Sautter, Robert; Ramos, Damaris; Schneper, Lisa et al. (2012) A complex multilevel attack on Pseudomonas aeruginosa algT/U expression and algT/U activity results in the loss of alginate production. Gene 498:242-53
Paletta, Janice L; Ohman, Dennis E (2012) Evidence for two promoters internal to the alginate biosynthesis operon in Pseudomonas aeruginosa. Curr Microbiol 65:770-5
Whitney, John C; Hay, Iain D; Li, Canhui et al. (2011) Structural basis for alginate secretion across the bacterial outer membrane. Proc Natl Acad Sci U S A 108:13083-8
Keiski, Carrie-Lynn; Harwich, Michael; Jain, Sumita et al. (2010) AlgK is a TPR-containing protein and the periplasmic component of a novel exopolysaccharide secretin. Structure 18:265-73
Thompson, Karl M; Abraham, Nabil; Jefferson, Kimberly K (2010) Staphylococcus aureus extracellular adherence protein contributes to biofilm formation in the presence of serum. FEMS Microbiol Lett 305:143-7

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