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Involvement of regulatory non-coding RNA in motility, biofilm formation, and adaptive antibiotic resistance in Pseudomonas aeruginosa Taylor, Patrick Kyle

Abstract

Small, non-coding RNA (sRNA) transcripts are emerging as a major mechanism for regulating translational expression in bacteria. Since the discovery of 6S RNA acting to regulate translation of RNA polymerases in Escherichia coli, our understanding of sRNA regulation of translation has expanded, and sRNAs are now known to have a broad range of functions in bacteria ranging from metabolic regulation to virulence determination. The Gram-negative bacterium Pseudomonas aeruginosa is commonly found in natural microbiomes, and is also an opportunistic pathogen as it causes disease in immunocompromised individuals. P. aeruginosa displays a high level of resistance to numerous clinically relevant antibiotics, and is capable of developing biofilms on multiple surfaces in hospital environments. P. aeruginosa is also capable of swarming which is a complex motility involving rhamnolipid surface whetting agents, flagella and type IV pili. This work investigated the involvement of 32 sRNA species in adaptive resistance to antibiotics, swarming motility, and biofilm formation in P. aeruginosa. Unique expression profiles under conditions of swarming and biofilm formation for 27 previously uncharacterized sRNAs were found. It was also found that the sRNAs prrF1, prrF2 and phrS are involved in swarming motility and/or biofilm formation. Compared to free-swimming, planktonic growth expression of the prrF gene loci was up-regulated 163- and 13-fold under swarming and biofilm conditions, respectively, and mutants lacking the entire locus demonstrated modest decreases in swarming while prrF1 mutants demonstrated increased biofilm formation. A transposon insertion mutant in phrS in P. aeruginosa PA14 wildtype displayed a deficiency in swarming motility and biofilm formation. phrS was also found to be involved in the development of adaptive resistance to polymyxin B by impacting on the translation of a lipid A modification operon. Together this work demonstrates that sRNA regulation plays a critical role in swarming motility, biofilm formation and the development of adaptive resistance in P. aeruginosa.

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