Comparison of liquid preservative for the long-term (2-month) preservation of nucliec acids

Autonomous biomolecular samplers, such as the Robotic Cartridge Sampling Instrument (RoCSI), rely on liquid preservatives to stabilize biomolecules, such as DNA and RNA, for subsequent ex-situ analysis. In this study, we compare four liquid preservatives, RNAlater® (Inivitrogen), RLT+ buffer (Qiagen), DNA/RNA Shield (Zymo Research), and Nucleic Acid Preservative (NAP), against samples that were flash-frozen and subsequently stored at -80°C. Results showed that both DNA and RNA can be preserved for two months with liquid preservatives, revealing comparable community composition and alpha diversity measures to flash frozen samples. DNA/RNA Shield (Zymo Research) was the only preservative to successfully preserve both DNA and RNA with yields sufficient for metabarcoding analysis. DNA/RNA Shield (Zymo Research) also produced the highest DNA yields and ASV counts from DNA metabarcoding. However, ASV counts from RNA metabarcoding were lower with DNA/RNA Shield (Zymo Research) compared to both RNAlater® (Qiagen) and NAP, with significant differences in beta diversity. This indicates that when RNA is the primary focus of an investigation, RNAlater® (Qiagen) or NAP may be preferable to DNA/RNA Shield (Zymo Research) for long-term (two-month) preservation. Understanding the temporal limits of liquid preservation methods is essential to maximize the utility of biomolecular samplers. This knowledge allows for extended intervals between sample exchanges, enabling sampling throughout challenging conditions, such as adverse weather events, remote locations, or outside normal working hours. Thereby, greatly increasing our capacity for consistent, high-resolution temporal and spatial biological observations.