Pseudomonas aeruginosa biofilm matrix polysaccharide Psl is regulated transcriptionally by RpoS and post-transcriptionally by RsmA.
Irie, Yasuhiko 1; Starkey, Melissa 2,+; Edwards, Adrianne N. 3; Wozniak, Daniel J. 4; Romeo, Tony 3,5; Parsek, Matthew R. 1,*
[Article] Molecular Microbiology. 78(1):158-172, October 2010.

(Format: HTML, PDF)

Summary: Extracellular polysaccharides are important components of biofilms. In non-mucoid Pseudomonas aeruginosa strains, the Pel and Psl polysaccharides are major structural components of the biofilm matrix. In this study, we demonstrate that the alternative [sigma]-factor RpoS is a positive transcriptional regulator of psl gene expression. Furthermore, we show that psl mRNA has an extensive 5' untranslated region, to which the post-transcriptional regulator RsmA binds and represses psl translation. Our observations suggest that upon binding RsmA, the region spanning the ribosome binding site of psl mRNA folds into a secondary stem-loop structure that blocks the Shine-Dalgarno sequence, preventing ribosome access and protein translation. This constitutes a novel mechanism for translational repression by this family of regulators.

Copyright (C) 2010 Blackwell Publishing Ltd.