Nature of bioavailability of DNA-intercalated polycyclic aromatic hydrocarbons to Sphingomonas sp.

The nature of bioavailability of DNA-intercalated PAHs in aqueous solution was investigated. The degradability of different PAHs including anthracene, phenanthrene and pyrene by Sphingomonas sp. was not inhibited even at a high DNA concentration of 2%. The DNA was stable against the PAH-degrader as indicated by the unchanged electrophoresis gel chromatograms after treatment. This shows that a structural change in the polymer is not necessary for the release of PAHs. Partitioning experiments using phenanthrene as a model PAH illustrated the presence of an initial passive uptake by autoclaved cells. Subsequent intracellular degradation became apparent from parallel data with live cells. Phenanthrene transfer from the DNA was diffusion-controlled and the exit of this molecule from their intercalation sites is favored in lieu of the presence of stronger hydrophobic binding sites in the cell membrane.