Involvement of the conserved small RNA SPA0122 in the regulation of virulence traits of Pseudomonas aeruginosa

Crucial traits contributing to pathogenicity of Pseudomonas aeruginosa are the production of a large assortment of virulence factors, biofilm formation and the ability to rapidly develop resistance to multiple classes of antibiotics. Expression of these traits is fine-tuned by a dynamic and intricate regulatory network [1], in which more than 50 regulatory proteins play key roles as transcription regulators. The involvement of small RNAs (sRNAs) in the P. aeruginosa virulence regulatory network has been underestimated, being so far less than ten the sRNAs shown to be implicated. We have recently performed a comparative sRNA profiling via deep-sequencing of P. aeruginosa PAO1 and PA14 strains [2] which share the same host range but differ in pathogenicity. We now aim to unravel virulence-relevant sRNA-based regulatory systems throughout the panel of novel sRNAs that we have identified. In this study, we have collected evidences for the involvement of the conserved sRNA SPA0122 in the regulation of two typical P. aeruginosa virulence traits: swimming motility and production of pyocyanin. In addition, we suggest that SPA0122 negatively regulates the expression of i) a key enzyme providing sugar precursors for the synthesis of exopolysaccarides, one of the biofilm matrix components, and ii) a protein involved in antibiotic susceptibility. Finally, we have evidences that SPA0122 is responsive to infection-relevant host stimuli such as oxygen availability and shift from room to body temperature. In conclusion, our results indicate that SPA0122, once receiving inputs from host sensing/signaling pathways, plays a role as global co-mediator of complex virulence regulatory sub-networks. 1. Balasubramanian D, Schneper L, Kumari H & Mathee K (2013) A dynamic and intricate regulatory network determines Pseudomonas aeruginosa virulence. Nucleic Acids Res, 41:1-20. 2. Ferrara S, Brugnoli M, De Bonis A, Righetti F, Delvillani F, Dehò G, Horner D, Briani F & Bertoni G (2012) Comparative Profiling of Pseudomonas aeruginosa Strains Reveals Differential Expression of Novel Unique and Conserved Small RNAs. PLoS One, 7:e36553.