Role of PrrF and PrrH regulation in Pseudomonas aeruginosa pathogenesis

项目总结

PROJECT SUMMARY 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 ΔprrF1,2 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.