The Small RNA ErsA of Pseudomonas aeruginosa Contributes to Biofilm Development and Motility through Post-transcriptional Modulation of AmrZ

Marilena Falcone, Silvia Ferrara, Elio Rossi, Helle K. Johansen, Søren Molin, Giovanni Bertoni

The small RNA ErsA ofPseudomonas aeruginosawas previously suggested to be involved in biofilm formation via negative post-transcriptional regulation of thealgCgene that encodes the virulence-associated enzyme AlgC, which provides sugar precursors for the synthesis of several polysaccharides. In this study, we show that a knock-outersAmutant strain forms a flat and uniform biofilm, not characterized by mushroom-multicellular structures typical of a mature biofilm. Conversely, the knock-out mutant strain showed enhanced swarming and twitching motilities. To assess the influence of ErsA on theP. aeruginosatranscriptome, we performed RNA-seq experiments comparing the knock-out mutant with the wild-type. More than 160 genes were found differentially expressed in the knock-out mutant. Parts of these genes, important for biofilm formation and motility regulation, are known to belong also to the AmrZ transcriptional regulator regulon. Here, we show that ErsA bindsin vitroand positively regulatesamrZmRNA at post-transcriptional levelin vivosuggesting an interesting contribution of the ErsA-amrZmRNA interaction in biofilm development at several regulatory levels.