Our overall goal is to define the bacterial stress response in Pseudomonas aeruginosa that activates genes for the production of the capsular polysaccharide alginate, an important virulence factor in pathogenesis and especially in pulmonary disease. P. aeruginosa is one of the most deadly opportunistic pathogens and is notorious for chronic pulmonary inflammation in cystic fibrosis (CF) and COPD patients. For 27 years, this NIH-sponsored program has been focused on understanding the complex regulatory machinery associated with alginate gene activation. Our recent studies revealed that alternative ECF sigma factor, sigma-22, is not only the main activator of alginate gene expression, but also the key regulator of an envelope / cell wall stress response system. We discovered that exposure of the bacteria to antibiotics that interfere with cell wall synthesis causes sigma-22 activation by an intra-membrane regulated proteolysis (RIP) mechanism. Using microarrays, we identified 293 protein gene products under positive control by sigma-22 and also several putative small RNAs (sRNA) that are likely to have important regulatory functions within the sigma-22 regulon. AlgB is two-component regulator of alginate gene activation, and we have discovered a phospho-mimic mutant of AlgB that can activate alginate biosynthesis by using sigma-54, which suggests an alternate pathway for expression of the algD operon for alginate biosynthesis. We have also obtained evidence that the large 5'upstream untranslated region (5'UTR) in the algD operon's mRNA modulates its expression. The overall goal of the next phase of these studies is to examine the hypothesis that important regulatory RNA mechanisms, which respond to envelope stress, lead to alginate gene activation. We will pursue 3 aims that are directed at understanding this global stress response that activates alginate genes: 1. Define the regulatory sRNAs induced by sigma-22 activation, 2. Characterize the AlgB and sigma-54 dependent alternative pathway for alginate gene expression, and 3. Define the role of the large upstream untranslated region (5'UTR) of the alginate operon in the regulation of alginate gene expression.

Public Health Relevance

Pseudomonas aeruginosa is one of the most deadly opportunistic pathogens and is notorious for chronic pulmonary inflammation in cystic fibrosis (CF) and COPD patients. This proposed research is to study the regulation of a capsular polysaccharide called alginate, which is an important virulence factor. Our overall goal is to focus on the regulatory RNA mechanisms that respond to envelope stress and lead to alginate and virulence gene activation.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
High Priority, Short Term Project Award (R56)
Project #
Application #
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Taylor, Christopher E,
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Virginia Commonwealth University
Schools of Medicine
United States
Zip Code
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 σ22 (AlgT/U) control in Pseudomonas aeruginosa. Microbiology 161:30-40
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:
Baker, Perrin; Ricer, Tyler; Moynihan, Patrick J et al. (2014) P. aeruginosa SGNH hydrolase-like proteins AlgJ and AlgX have similar topology but separate and distinct roles in alginate acetylation. PLoS Pathog 10:e1004334
King, Allison; Chakrabarty, Souvik; Zhang, Wei et al. (2014) High antimicrobial effectiveness with low hemolytic and cytotoxic activity for PEG/quaternary copolyoxetanes. Biomacromolecules 15:456-67
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
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
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
Wood, Lynn F; Ohman, Dennis E (2012) Identification of genes in the ýýýýýý regulon of Pseudomonas aeruginosa required for cell envelope homeostasis in either the planktonic or the sessile mode of growth. MBio 3:
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