Identification and characterization of new targets of the small RNA ErsA of Pseudomonas aeruginosa

In bacterial pathogens, small RNAs (sRNAs) have been recognized as key elements of the regulatory networks for the coordinate expression of the virulence factors underlying the interaction with host . ErsA is a novel Pseudomonas aeruginosa sRNA responsive to infection-relevant host stimuli such as oxygen availability and temperature shift, and its transcription is under the control of the lternative sigma factor σ22 (AlgT/U), a mediator of the stress response implicated in the bacterium pathogenicity. ErsA has been shown to be linked to anabolic functions for the synthesis of exoproducts from sugar precursors. Specifically, in PAO1 strain ErsA directly exerts a negative post-transcriptional regulation on the virulence-associated algC gene for the bifunctional enzyme AlgC. In addition, we have shown that ErsA is involved in antibiotic susceptibility, pyocyanin production, swimming and swarming motility. Since it is known that sRNAs can modulate a multitude of target mRNAs, we now aim at the characterization of novel target genes regulated by ErsA in order to expand the knowledge about the ErsA-based regulatory network. To achieve this goal, we have used bioinformatics tools to generate a short list of putative direct targets among which we have selected genes involved in i) envelope architecture/homeostasis, ii) alginate and motility regulation, iii) exopolysaccharides production, iv) antibiotic resistance. We are currently evaluating the regulatory role of ErsA on these target genes through the use of in vivo translational fusion based on gfp reporter gene; in vitro mobility shift assays and phenotypic assays on mutant strains.