DNA, RNA, and prokaryote community sample stability at different ultra-low temperature storage conditions

Abstract Long-term storage of extracted DNA, RNA, and samples for DNA and RNA extractions is usually done in ultra-low temperature freezers using the standard temperature of −80°C. While this standard was based on the maximum capacity of early generation ultra-low temperature freezers, this paradigm is challenged and initiatives support a switch to −70°C to save energy, reduce heat production, and increase the life expectancy of the freezers. The question arising from these initiatives regards the safety of the samples. Especially in complex biological samples, such as sediments, changes in long-term storage temperature have not been studied in detail. Here, we show that the concentration of extracted nucleic acids and nucleic acids in tissue or cells stored at both temperatures does not differ significantly from each other. The only significant differences found were explained by the variability within the samples over time but not between different temperatures or by dilution factor. In addition, we show that prokaryote community composition in sediment and DNA samples also remain stable at both temperatures. Only two treatments were significantly different in temperature, indicating that for RNA, storage at −70°C might be preferable. Consequently, we recommend storing samples for nucleic acid work at −70°C to reduce energy consumption and support more sustainable lab practices.