Abstract
Bacterial adhesion and biofilm formation are both dependent on the production of extracellular polymeric substances (EPS) mainly composed of polysaccharides, proteins, lipids, and extracellular DNA (eDNA). eDNA promotes biofilm establishment in a wide range of bacterial species. In Pseudomonas aeruginosa eDNA is major component of biofilms and is essential for biofilm formation and stability. In this study we report that production of pyocyanin in P. aeruginosa PAO1 and PA14 batch cultures is responsible for promotion of eDNA release. A phzSH mutant of P. aeruginosa PAO1 that overproduces pyocyanin displayed enhanced hydrogen peroxide (H2O2) generation, cell lysis, and eDNA release in comparison to its wildtype strain. A ΔphzA-G mutant of P. aeruginosa PA14 deficient in pyocyanin production generated negligible amounts of H2O2 and released less eDNA in comparison to its wildtype counterpart. Exogenous addition of pyocyanin or incubation with H2O2 was also shown to promote eDNA release in low pyocyanin producing (PAO1) and pyocynain deficient (PA14) strains. Based on these data and recent findings in the biofilm literature, we propose that the impact of pyocyanin on biofilm formation in P. aeruginosa occurs via eDNA release through H2O2 mediated cell lysis.
Highlights
Bacterial adhesion and biofilm formation represent significant and ongoing problems in contexts ranging from lethal bacterial infections to corrosion of engineered systems [1,2,3]
Pyocyanin production and extracellular DNA (eDNA) release were quantified in pyocyanin producing and pyocyanin deficient strains of P. aeruginosa
P. aeruginosa produces a variety of phenazines which were formerly disregarded as bacterial secondary metabolites but have recently garnered much attention and been ascribed a variety of roles in microbial ecology
Summary
Bacterial adhesion and biofilm formation represent significant and ongoing problems in contexts ranging from lethal bacterial infections to corrosion of engineered systems [1,2,3]. A decade ago, Whitchurch and coworkers discovered that eDNA is a major component of biofilms formed by the opportunistic human pathogen Pseudomonas aeruginosa and is essential for biofilm formation and stability [6]. Since these seminal findings were made, it has been shown that eDNA promotes initial bacterial adhesion, cellular aggregation, biofilm strength and protection of bacterial cells in biofilms against antibiotics and detergents in a wide range of bacteria [7,8,9,10,11,12,13]. In other Streptococcus species pyruvate oxidase has been implicated in cell lysis and eDNA release via H2O2 generation [17,18]
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