Nucleic acid contamination of glycogen used in nucleic acid precipitation and assessment of linear polyacrylamide as an alternative co-precipitant.

Molecular-grade glycogen is widely used to recover nanogram or picogram quantities of DNA and RNA across molecular biology applications in the life sciences. As a result, its purity is critical to obtain reliable results. Using agarose gel electrophoresis, we detected pg/microL (DNA) to ng/microL (RNA) concentrations of nucleic acid in two of the nine glycogen samples obtained from commercial suppliers. Denaturing gradient gel electrophoresis of 16S rRNA gene PCR-amplified products indicated that an additional two samples contained detectable contamination. We also tested a synthetic polymer co-precipitant, linear polyacrylamide (LPA); none of the four samples tested with LPA were detectably contaminated. The partial 16S rRNA gene sequence associated with the contaminated samples of the shellfish-derived glycogen was nearly identical to the sequence of Actinobacteria lwoffii, which has been isolated from mussels previously. By testing the recovery of low-nanogram amounts of DNA with multiple precipitants and simulated experimental conditions, we demonstrated that LPA was a preferable co-precipitant for sensitive protocols.