Barraud, Nicolas, Hassett, Daniel J., Hwang, Sung-Hei, Rice, Scott A., Kjelleberg, Staffan and Webb, Jeremy S.
Involvement of nitric oxide in biofilm dipsersal of Pseudomonas aeruginosa.
Journal of Bacteriology, 188, (21), . (doi:10.1128/JB.00779-06).
Bacterial biofilms at times undergo regulated and coordinated dispersal events where sessile biofilm cells
convert to free-swimming, planktonic bacteria. In the opportunistic pathogen Pseudomonas aeruginosa, we
previously observed that dispersal occurs concurrently with three interrelated processes within mature biofilms:
(i) production of oxidative or nitrosative stress-inducing molecules inside biofilm structures, (ii) bacteriophage
induction, and (iii) cell lysis. Here we examine whether specific reactive oxygen or nitrogen
intermediates play a role in cell dispersal from P. aeruginosa biofilms. We demonstrate the involvement of
anaerobic respiration processes in P. aeruginosa biofilm dispersal and show that nitric oxide (NO), used widely
as a signaling molecule in biological systems, causes dispersal of P. aeruginosa biofilm bacteria. Dispersal was
induced with low, sublethal concentrations (25 to 500 nM) of the NO donor sodium nitroprusside (SNP).
Moreover, a P. aeruginosa mutant lacking the only enzyme capable of generating metabolic NO through
anaerobic respiration (nitrite reductase, nirS) did not disperse, whereas a NO reductase mutant (norCB)
exhibited greatly enhanced dispersal. Strategies to induce biofilm dispersal are of interest due to their potential
to prevent biofilms and biofilm-related infections. We observed that exposure to SNP (500 nM) greatly
enhanced the efficacy of antimicrobial compounds (tobramycin, hydrogen peroxide, and sodium dodecyl
sulfate) in the removal of established P. aeruginosa biofilms from a glass surface. Combined exposure to both
NO and antimicrobial agents may therefore offer a novel strategy to control preestablished, persistent P.
aeruginosa biofilms and biofilm-related infections.
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