Insights into DNA stability (Part 2)

First, a quick recap of how the experiment was carried out:

To evaluate the feasibility of room temperature shipping for extracted DNA samples, DNA was extracted from a single environmental wastewater sample following Resistomap SOP. The extracted DNA was aliquoted and stored at room temperature, and DNA concentration and quality measurements were conducted at multiple time points over a 26-day period to assess stability. Aliquots were stored at -20°C after each time series point prior to SmartChip qPCR analysis.

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Last time we shared the DNA concentration and purity results from our quality control procedures, showing that extracted DNA stored at room temperature remained stable and reliable for at least 2 weeks.  If you haven't seen the previous post, we suggest you start by reading part 1.

This time, we move to the next phase of the experiment: quantifying antibiotic resistance genes (ARGs) in these samples. Running a full HT-qPCR analysis will help determine whether any significant DNA fragmentation or other issues occurred during room-temperature storage.

So far, the analytical results remain promising. The samples presented here were taken on days 1, 5, 12, and 26 to provide an initial overview. Using the Resistomap Platform, we visualised the results in a bar chart, which gives an indication of consistency across sample runs. While the pattern on day 26 appears different from earlier time points, the correlation analysis suggests overall consistency. Interestingly, despite the visual differences, the pairwise Pearson correlation values (r) for days 12 and 26 compared to day 1 are nearly identical (0.930 and 0.933, respectively), reinforcing the reproducibility of the data as shown in the image below.

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For the microbial biologists reading, you can access the full dataset and explore a heat-map of specific detected genes and their copy numbers through our open-access project on the Resistomap Platform for a deeper look into the genetic composition. Here is a screen capture of the heat-map filtered to only show genes related to β-lactams.

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Key takeaways:

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• The sample analysis results indicate minimal or negligible DNA fragmentation for at least 12 days at room temperature.
• A noticeable difference appeared on day 26, but the DNA remained suitable for analysis.
• These findings further validate that shipping extracted DNA at ambient temperature is a reliable option for short-term sample transport.
• As an initial assessment, this experiment provides a positive indication that shipping extracted DNA at room temperature is a viable option. We will share a more in-depth follow-up on this topic in the future.
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Summary and bonus‍

So, what does this all mean? Simply put, shipping extracted DNA at ambient temperature is looking to be a solid option for short-term transport. And beyond just feasibility, it comes with added benefits: room-temperature shipments are about 600% smaller in volume and weight compared to dry ice shipments.

To put that into concrete numbers, using the Well-to-Wheel (WtW) measurements for CO₂ emissions, a typical dry ice shipment between Finland and the UK as example contributes 26.76 kg CO₂e WtW, while a room-temperature shipment only contributes 3.57 kg CO₂e WtW. These are approximations, but even with a generous margin for error, the difference in CO₂ emissions is compelling. And every small victory for the environment counts (One Health).

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Whats next?

Thank you for reading! This proof-of-concept experiment has received significant interest, and while the results are very promising, we aim to conduct a deeper analysis. In the future, we plan to gather more data, including biological replicates and additional sample types, to strengthen our conclusions scientifically.

In the meantime, we’ll soon be merging both parts of this initial two-part post into a single article summary. The demo project remains open for exploration, so feel free to check out the open-access project on our platform and explore the analysis results yourself.

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