Note: the data displayed was generated using our legacy chemistry (SQK-LSK109), but the outcomes and recommendations are still applicable to our current chemistry.

We are in the process of investigating the stability of extracted genomic DNA over time when stored at different temperatures. DNA was extracted from a Bacillus subtilis cell pellet using the QIAGEN Genomic-tip procedure as outlined in the product details. The extracted DNA was eluted in TE buffer, aliquoted and stored at 4°C or -20°C. After set periods of time over twelve months, aliquots are removed from storage and libraries prepared for sequencing using our Ligation Sequencing Kit. Prior to sequencing, the samples were SPRI size-selected.

In Figure 1, data is presented on the effect of the different storage conditions on read N50. No impact on sequencing throughput was observed and all samples delivered 3-star performance: 8+ Gb in 48 hours on flow cell FLO-MIN106, equivalent to the Lambda DNA supplied with the Control Expansion pack (EXP-CTL001).

Figure 1. The effect of storage of DNA at -20°C or at 4°C on the observed read N50 of DNA sequencing libraries. These data indicate some deterioration of read N50 may be observed when storing DNA at 4°C over a period of 6 months. Therefore, storage at -20°C is advised to maintain sample integrity.