Soot and charcoal are reservoirs of extracellular DNA

Soot and charcoal are carbonaceous materials widespread in the environment where they readily can come in contact with extracellular DNA shed from organisms. The adsorption at a surface protects DNA from chemical and biological degradation. However, a comprehensive insight into DNA adsorption at soot and charcoal is lacking. We measured DNA adsorption capacity at soot and charcoal as a function of solution composition, time and DNA length. We observed that the capacity for DNA is the highest at low pH, 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. We demonstrate how the interaction between DNA and soot and charcoal partly occurs via terminal basepairs, suggesting that, besides electrostatic forces, hydrophobic interactions play an important role in binding. The importance of hydrophobic interactions increases as the hydrophobicity of a surface increases. Such strong binding and hydrophobic interactions need to be taken into account to improve DNA extraction protocols and for mitigation of the spread of antibiotic resistance genes in environmental matrices that contain soot and charcoal such as aerosol, wastewater and topsoil.