Soot and charcoal as reservoirs of extracellular DNA

The vast potential of using sediment adsorbed DNA as a window to past and present biodiversity rely on the ability of solid surfaces to adsorb environmental DNA. However, a comprehensive insight into DNA adsorption at surfaces in general is lacking. Soot and charcoal are carbonaceous materials widespread in the environment where they readily can come in contact with extracellular DNA shed from organisms. Using batch adsorption, we measured DNA adsorption capacity at soot and charcoal as a function of solution composition, time and DNA length. We observed that the adsorption capacity for DNA is highest at low pH, that it increases with solution concentration and cation valency and that the activation energy for DNA adsorption at both soot and charcoal is ~50 kJmol-1, suggesting strong binding. We demonstrate how the interaction between DNA and soot and charcoal partly occurs via terminal base pairs, suggesting that, besides electrostatic forces, hydrophobic interactions play an important role in binding. The large adsorption capacities and strong binding of DNA to soot and charcoal are features important for eDNA research and provide a motivation for use of carbonaceous materials from, e.g. anthropogenic pollution or wildfire as sources of biodiversity information.