Evaluating the efficacy of various thermo-stable polymerases against co-extracted PCR inhibitors in ancient DNA samples

DNA from ancient and forensic specimens is often co-extracted with unknown amounts of unknown PCR inhibitors, which can lead to underestimated DNA concentrations, allelic drop-out, and/or false-negative results. It is not surprising, in this case, that numerous methods have been developed to remove PCR inhibitors or subdue their effects. One simple and cost effective approach could be the adoption of a polymerase that overcomes or is less affected by PCR inhibitors. In this study, nine different polymerases were evaluated for their efficacy against PCR inhibitors co-extracted with DNA from 63 ancient salmon vertebrae. These samples were excavated from two archeological sites located at the Dionisio Point locality on the northern end of Galiano Island in coastal southwestern British Columbia, Canada and date to 700–1000 and 1300–1500 years before present. Previously, DNA extracts from samples studied from this locality were determined to be largely inhibited to PCR amplification. In the present study, Omni Klentaq LA (DNA Polymerase Technology, Inc.) outperformed the other 8 polymerases in two measures: (1) its success in genetic species identification of these vertebrae, and (2) its ability to amplify an ancient DNA positive control when spiked with a volume of potentially inhibited extract from the vertebrae.