Minimal attachment of Pseudomonas aeruginosa to DNA modified surfaces

Extracellular deoxyribonucleic acid (eDNA) exists in biological environments such as those around medical implants since prokaryotic or eukaryotic cells can undergo processes such as autolysis, necrosis, and apoptosis. For bacteria, eDNA has been shown to be involved in biofilm formation and gene transfer and acts as a nutrient source. In terms of biofilm formation, eDNA in solution has been shown to be very important in increasing attachment; however, very little is known about the role played by surface immobilized eDNA in initiating bacterial attachment and whether the nature of a DNA layer (physically adsorbed or covalently attached, and molecular weight) influences biofilm formation. In this study, the authors shed light on the role that surface attached DNA plays in the early biofilm formation by using Si wafers (Si) and allylamine plasma polymer (AAMpp) coated Si wafers to adsorb and covalently immobilize salmon sperm DNA of three different molecular weights. Pseudomonas aeruginosa was chosen to study the bacterial interactions with these DNA functionalized surfaces. Characterization of surface chemistry and imaging of attached bacteria were performed via x-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and epi-fluorescence microscopy. XPS results confirmed the successful grafting of DNA on the AAMpp and Si surfaces, and surprisingly the results showed that the surface attached DNA actually reduced initial bacterial attachment, which was contrary to the initial hypothesis. This adds speculation about the specific role played by DNA in the dynamics of how it influences biofilm formation, with the possibility that it could actually be used to make bacterial resistant surfaces.