ThePseudomonas aeruginosaPrrF sRNAs promote biofilm formation at body temperature

Pseudomonas aeruginosais a Gram-negative opportunistic pathogen that causes both acute and chronic infections in vulnerable populations. Treatment ofP. aeruginosainfections is increasingly challenging due to multi-drug resistance as well as biofilm formation that further increases antibiotic tolerance. Iron, which is sequestered by the host innate immune system, is also a key nutrient that required forP. aeruginosabiofilm formation. Previous work showed that the iron-responsive PrrF small regulatory RNAs (sRNAs), which are key toP. aeruginosa’siron starvation response and required for virulence in murine lung infection, are dispensable for biofilm formation. However, these studies were performed using flow-cell biofilms at room temperature. Here we demonstrate a temperature dependency for PrrF inP. aeruginosabiofilm formation – the genes for these sRNAs are required for optimal biofilm formation at 37°C but not 25°C. We further show that the ΔprrFmutant lacks a yet-to-be identified surface appendage that is produced at 37°C but not 25°C. These studies demonstrate that the importance of the PrrF sRNAs inP. aeruginosabiofilm formation at body temperature and reveal a previously under-appreciated role of temperature in iron homeostasis andP. aeruginosabiofilm physiology.