4.4 Article

SagS Contributes to the Motile-Sessile Switch and Acts in Concert with BfiSR To Enable Pseudomonas aeruginosa Biofilm Formation

Journal

JOURNAL OF BACTERIOLOGY
Volume 193, Issue 23, Pages 6614-6628

Publisher

AMER SOC MICROBIOLOGY
DOI: 10.1128/JB.00305-11

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Funding

  1. Army Research Office [W911NF0710604]
  2. National Institutes of Health [2R15 HL073835-02]

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The interaction of Pseudomonas aeruginosa with surfaces has been described as a two-stage process requiring distinct signaling events and the reciprocal modulation of small RNAs (sRNAs). However, little is known regarding the relationship between sRNA-modulating pathways active under planktonic or surface-associated growth conditions. Here, we demonstrate that SagS (PA2824), the cognate sensor of HptB, links sRNA-modulating activities via the Gac/HptB/Rsm system postattachment to the signal transduction network BfiSR, previously demonstrated to be required for the development of P. aeruginosa. Consistent with the role of SagS in the GacA-dependent HtpB signaling pathway, inactivation of sagS resulted in hyperattachment, an HptB-dependent increase in rsmYZ, increased Psl polysaccharide production, and increased virulence. Moreover, sagS inactivation rescued attachment but abrogated biofilm formation by the Delta gacA and Delta hptB mutant strains. The Delta sagS strain was impaired in biofilm formation at a stage similar to that of the previously described two-component system BfiSR. Expression of bfiR but not bfiS restored Delta sagS biofilm formation independently of rsmYZ. We demonstrate that SagS interacts directly with BfiS and only indirectly with BfiR, with the direct and specific interaction between these two membrane-bound sensors resulting in the modulation of the phosphorylation state of BfiS in a growth-mode-dependent manner. SagS plays an important role in P. aeruginosa virulence in a manner opposite to that of BfiS. Our findings indicate that SagS acts as a switch by linking the GacA-dependent sensory system under planktonic conditions to the suppression of sRNAs postattachment and to BfiSR, required for the development of P. aeruginosa biofilms, in a sequential and stagespecific manner.

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