The Pseudomonas aeruginosa PrrF Small RNAs Regulate Iron Homeostasis during Acute Murine Lung Infection.

is a Gram-negative opportunistic pathogen that requires iron for virulence. Iron homeostasis is maintained in part by the PrrF1 and PrrF2 small RNAs (sRNAs), which block the expression of iron-containing proteins under iron-depleted conditions. The PrrF sRNAs also promote the production of the quinolone signal (PQS), a quorum sensing molecule that activates the expression of several virulence genes. The tandem arrangement of the genes allows for expression of a third sRNA, PrrH, which is predicted to regulate gene expression through its unique sequence derived from the intergenic (IG) sequence (the PrrH sequence). Previous studies showed that the locus is required for acute lung infection. However, the individual functions of the PrrF and PrrH sRNAs were not determined. Here, we describe a system for differentiating PrrF and PrrH functions by deleting the PrrH sequence [(ΔH)]. Our analyses of this construct indicate that the PrrF sRNAs, but not PrrH, are required for acute lung infection by Moreover, we show that the virulence defect of the Δ mutant is due to decreased bacterial burden during acute lung infection. analysis of gene expression in lung homogenates shows that PrrF-mediated regulation of genes for iron-containing proteins is disrupted in the Δ mutant during infection, while the expression of genes that mediate PrrF-regulated PQS production are not affected by deletion Combined, these studies demonstrate that regulation of iron utilization plays a critical role in 's ability to survive during infection.