Pseudomonas aeruginosa is a versatile bacterial pathogen that causes life-threatening acute and chronic infections in diverse patient populations. Complicating treatment is the ability of P. aeruginosa to resist the majority of antimicrobial therapies. It is therefore critical to identify virulence properties that can be targeted for the development of novel therapeutics. Several studies demonstrate the importance of iron homeostasis for P. aeruginosa pathogenesis. Recent work from our lab shows that the P. aeruginosa prrF chromosomal locus, which encodes the iron-responsive PrrF1 and PrrF2 small regulatory RNAs (sRNAs), is required for acute lung infection in mice. The PrrF1 and PrrF2 sRNAs contribute to iron homeostasis by repressing the expression of iron-utilizing pathways when this nutrient is limiting. This ?iron sparing response? further impacts diverse virulence properties, including quorum sensing and biofilm formation. The prrF locus produces a distinct sRNA (PrrH) that is regulated by heme, an abundant source of iron in the human body, thus linking iron and heme homeostasis pathways of P. aeruginosa. While our studies have established the broad impact of this locus on P. aeruginosa physiology and virulence, the mechanisms by which the individual sRNAs transcribed from this locus mediate gene expression and pathogenesis remain unknown. Based on our preliminary and published studies, we hypothesize that the PrrF and PrrH sRNAs play critical yet distinct roles in regulating P. aeruginosa iron homeostasis and virulence. We will test our hypothesis by 1) identifying PrrF target mRNAs responsible for virulence attenuation of the ?prrF1,2 mutant; 2) determining the genetic basis of heme regulated expression via the PrrH sRNA; and 3) defining the mechanisms by which PrrF and PrrH regulate gene expression. These studies will define the specific mechanisms by which the prrF-transcribed sRNAs mediate iron homeostasis and virulence of P. aeruginosa.

Public Health Relevance

Pseudomonas aeruginosa is a bacterial pathogen that causes life-threatening infections in patients with a variety of underlying conditions, including cancer and cystic fibrosis. P. aeruginosa is resistant to most current antibiotics, making the identification of new antimicrobial targets a public health priority. Our lab previously showed that three iron-regulated small RNA molecules are required for P. aeruginosa to cause infection. The proposed work will define the mechanism by which these RNA molecules allow for infection, with the long term goal of targeting these RNA molecules to treat P. aeruginosa infections.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Bacterial Pathogenesis Study Section (BACP)
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Lu, Kristina
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University of Maryland Baltimore
Schools of Pharmacy
United States
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Reinhart, Alexandria A; Nguyen, Angela T; Brewer, Luke K et al. (2017) The Pseudomonas aeruginosa PrrF Small RNAs Regulate Iron Homeostasis during Acute Murine Lung Infection. Infect Immun 85:
Reinhart, Alexandria A; Oglesby-Sherrouse, Amanda G (2016) Regulation of Pseudomonas aeruginosa Virulence by Distinct Iron Sources. Genes (Basel) 7: