The roles of extracellular DNA in bacterial biofilm formation
Bacterial biofilm formation is dependent upon production of extracellular polymeric substances (EPS) mainly composed of polysaccharides, proteins, lipids and extracellular DNA (eDNA). eDNA promotes initial bacterial adhesion, aggregation, biofilm formation in a wide range of bacterial species. In Pseudomonas aeruginosa eDNA is a major component of biofilms and is essential for biofilm formation and stability. P. aeruginosa also produces phenazine an electrochemically active metabolite and phenazine production promotes eDNA release. The relationship between eDNA release and phenazine production is bridged via hydrogen peroxide (H2O2) generation and subsequent H2O2 mediated cell lysis and ultimately release of chromosomal DNA into the extracellular environment as eDNA. Recent investigation showed pyocyanin (a kind of phenazine predominantly produced by P. aeruginosa) binds to eDNA mediated through intercalation of pyocyanin with eDNA. Pyocyanin binding to DNA has significant impacts on DNA properties and also on P. aeruginosa cell surface properties including its hydrophobicity, attractive surface energies physico-chemical interactions and bacterial aggregation.