The novel small RNA SPA0084 has pleiotropic effects on virulence traits linked to quorum sensing in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an important opportunistic pathogen in immune-compromised and cystic fibrosis patients, responsible for acute and chronic infections. It produces a large arsenal of virulence factors and is endowed with enhanced capability of biofilm formation. The expression of these virulence traits is fine-tuned by a dynamic and intricate regulatory network [1], in which quorum sensing (QS) has central role. In bacterial pathogens, small RNAs (sRNAs) have been recognized as key elements of the coordinate expression of the virulence factors underlying the interaction with host [2]. In this work, we suggest that the novel sRNA SPA0084 of P. aeruginosa [3] is linked to the las QS network [4]. Our results show that SPA0084 is up-regulated in mutants of lasR and lasI, two key QS genes for the LasI synthase of 3-oxo-C12-homoserine lactone (3OC12HSL), and for LasR receptor of 3OC12HSL, respectively. SPA0084 is also responsive to infection-relevant cues that P. aeruginosa can experience in mammalian hosts like limited iron availability, temperature shifts from environmental to body temperature and reduced oxygen conditions. Moreover, we show that, following overexpression, SPA0084 has pleiotropic effects on virulence traits linked to QS such as motility, pyoverdine, pyocyanin, protease, emolytic activity as long as biofilm formation. Finally, we predicted in silico and validated both in vitro and in vivo by using a GFP-based reporter system that SPA0084 can target the mRNAs of lasR and lasI. Therefore, SPA0084 could influence QS-regulated virulence traits via the modulation of lasR and lasI genes. 1. Balasubramanian et al. (2013) A dynamic and intricate regulatory network determines Pseudomonas aeruginosa virulence. Nucleic Acids Res, 41:1-20. 2. Caldelari et al. (2013) RNA-mediated regulation in pathogenic bacteria. Cold Spring Harb Perspect Med, 2013;3:a010298. 3. Ferrara et al. (2012) Comparative profiling of Pseudomonas aeruginosa strains reveals differential expression of novel unique and conserved small RNAs. PLoS One, 7:e36553. 4. Rutherford ST, Bassler BL (2012) Bacterial quorum sensing: its role in virulence and possibilities for its control. Cold Spring Harb Perspect Med, 2012;2:a012427.