Role of extracellular DNA in biofilm formation by Staphylococcus aureus

Biofilms are communities of bacteria, surrounded by a self-produced extracellular matrix, growing attached to a tissue or surface. The biofilm mode of growth protects bacteria from cell stressors such as antibiotics and desiccation, and is thought to play a role in up to 80% of human infections. The biofilm matrix is composed of polymers such as proteinaceous pili, exopolysaccharides and double-stranded DNA. This study investigated the role of extracellular DNA (eDNA) in biofilms formed by Staphylococcus aureus, an important human pathogen. By using a microtiter plate crystal violet binding assay, agarose gel electrophoresis, and confocal scanning laser microscopy, we found that eDNA plays an important structural and adhesive role in S. aureus biofilms. We further found that DNase is a potent inhibitor of S. aureus biofilm formation and found that many environmental bacteria produce DNases that inhibit S. aureus biofilm formation. The results of these studies confirm that eDNA mediates cell-to-cell interactions in bacterial biofilms and suggest that eDNA warrants further consideration as an antimicrobial drug target.