Carbon stable isotope composition of DNA isolated from an incipient paleosol

We determined the carbon isotope (delta (super 13) C) value of double-stranded DNA (dsDNA) isolated from the organic horizons of a Delaware soil that is actively being covered by an encroaching sand dune. The soil belongs to a Nymphaea odorata Ait. (water lily) wetland, and we regard its active acquisition of a thick ( approximately 24 cm) surface mantle to embody the process of paleopedogenesis; therefore, we have termed it an "incipient paleosol." In this study, we compared the delta (super 13) C value of paleosol dsDNA to the bulk delta (super 13) C value of N. odorata, as well as to the delta (super 13) C value of plants that had colonized the surface mantle. The isotopic offset between paleosol delta (super 13) C (sub dsDNA) and N. odorata delta (super 13) C (sub tissue) was identical to the relationship between delta (super 13) C (sub dsDNA) and delta (super 13) C (sub tissue) for tracheophytes, which we had previously determined. In contrast, the isotopic offset between paleosol delta (super 13) C (sub dsDNA) and the delta (super 13) C (sub tissue) of plants colonizing the surface mantle differed from this relationship by as much as 4ppm. Similarly, the delta (super 13) C value of bulk paleosol organic matter was extremely heterogeneous and varied across 6ppm. All paleosol DNA polymerase chain reaction (PCR) products produced clear, sharp, 350 base-pair (bp) fragments of rbcL, a gene shared by all photosynthetic organisms. These results open the exciting possibility that stable isotope analysis of dsDNA isolated from paleosol organic matter can be used to infer the delta (super 13) C value of the plant that dominated the nucleic acid contribution.