Interaction between humic acids and DNA: an FT-IR approach

Several studies conducted in microcosms have indicated the importance of soil particles (i.e., clay, sand, and humic acids) in the protection of DNA against degradation by nucleases, such as DNase and restriction endonucleases (Yin and Stotzky 1997; Crecchio and Stotzky 1998). In addition, the persistence of extacellular DNA is one of the most important factor to determine the horizontal transfer of extracellular genes among bacteria in soil environment (Yin and Stotzky 1997; Crecchio and Stotzky 1998). Therefore it is important to determine the factors that affect the persistence of extracellular DNA in natural environment, and in particular a) to determine how DNA binds on soil particles, and b) to explain how extracellular DNA persists in soil. The main purpose of the present work was to study the role of the humic acids, as soil aggregates, in the persistence of DNA in soils. A fourier-transform infrared (FT-IR) analysis was used to determine possible changes in the conformational structure of DNA and the chemical groups involved in binding with humic acids and DNA.