# The Pseudomonas aeruginosa PrrF sRNAs and PqsA promote biofilm formation at body temperature

## TL;DR

This study shows that Pseudomonas aeruginosa uses specific RNA molecules to form biofilms at body temperature, which is important for its ability to cause infections.

## Contribution

The study reveals a temperature-dependent role of PrrF sRNAs in P. aeruginosa biofilm formation at 37°C.

## Key findings

- PrrF sRNAs are required for optimal biofilm formation at 37°C but not at 25°C.
- A ∆pqsA mutant mimics the biofilm defect of a ∆prrF mutant, linking PQS to PrrF function.
- Temperature significantly affects P. aeruginosa biofilm physiology and iron homeostasis.

## Abstract

Pseudomonas aeruginosa is a gram-negative opportunistic pathogen that causes both acute and chronic infections in vulnerable populations. Treatment of P. aeruginosa infections is increasingly challenging due to multi-drug resistance, and biofilm formation during infection further increases antibiotic tolerance. Iron, which is sequestered by the host innate immune system, is also a key nutrient that is required for P. aeruginosa biofilm formation. The iron-responsive PrrF small regulatory RNAs (sRNAs) are key to P. aeruginosa’s iron starvation response, promote the production of the Pseudomonas quinolone signal (PQS) quorum sensing molecule, and are required for virulence in murine lung infection. Prior work showed that the PrrF sRNAs are dispensable for biofilm formation; however, these studies were performed using flow-cell biofilms grown at room temperature. Here, we demonstrate a temperature dependency for PrrF in P. aeruginosa biofilm formation: the genes for these sRNAs are required for optimal biofilm formation at 37°C but not 25°C. We further show that a ∆pqsA mutant, which lacks production of PQS and related metabolites, phenocopies the ∆prrF mutant. These studies demonstrate the importance of the PrrF sRNAs in P. aeruginosa biofilm formation at body temperature and reveal a previously underappreciated role of temperature in iron homeostasis and P. aeruginosa biofilm physiology.

Biofilm formation is a critical virulence trait for many microbial pathogens that confers tolerance to the host immune system and antimicrobials. Pseudomonas aeruginosa is an opportunistic pathogen that forms biofilms resulting in treatment failure. Iron is a known requirement for P. aeruginosa biofilm formation, yet the precise role of iron in biofilm physiology remains unclear. Here, we show that temperature alters the requirement for the PrrF small regulatory RNAs, key components of P. aeruginosa’s iron starvation response, for biofilm formation. Specifically, PrrF is required for the optimal formation of flow-cell biofilms at 37°C but not at 25°C, yet most flow-cell biofilm studies are conducted at 25°C. These results demonstrate a previously underappreciated role of temperature in P. aeruginosa biofilm physiology.