Pseudomonas aeruginosa biofilm matrix polysaccharide Psl is regulated transcriptionally by RpoS and post-transcriptionally by RsmA.
Bottom Line: In this study, we demonstrate that the alternative σ-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.This constitutes a novel mechanism for translational repression by this family of regulators.
Affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195, USA.Show MeSH
Mentions: In P. aeruginosa, RpoS is an alternative σ-factor that regulates expression of a number of genes in the stationary phase (Schuster et al., 2004). Schuster et al. observed that all the genes in the psl operon (pslA-L) were upregulated during stationary-phase growth in wild-type (WT) PAO1, but not in an isogenic ΔrpoS mutant strain. We therefore tested whether RpoS controls psl transcription. As shown by quantitative real-time polymerase chain reaction (PCR) in Fig. 3A, psl transcripts increased about threefold in stationary phase compared with mid-log phase in WT cultures, but ΔrpoS failed to show an increase in psl transcription during stationary phase. To confirm a functional consequence for the RpoS-dependent increase in psl transcription in stationary phase, we analysed relative Psl levels using Psl-specific antisera (Fig. 3D). As predicted from the quantitative real-time PCR data, the amount of Psl produced by WT and ΔrpoS were low during mid-log phase, and only WT increased during stationary phase.
Affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195, USA.