Reacción a "The remains of Ötzi, the ‘Iceman’, harbor modern and ancient microorganisms"

The article by Sahan and colleagues investigates the microbiome of the mummified remains of the famous Ötzi the Iceman, 5,300 years old, preserved for three decades in the Tyrol Museum (Austria) at low temperatures (-6°C). The question they attempt to answer is relevant: can the preservation conditions preserve the ancestral microbiota or, on the contrary, do they allow the survival and growth of microorganisms that may have colonized the mummified remains? To this end, the team employs appropriate techniques combining metagenomics, isolation by culture, and detection of DNA damage characteristic of ancient samples. The methodology used is appropriate, and although the study has obvious limitations (such as the small number of samples and lack of replicates), the results are conclusive.

The main results are clear and demonstrate that the studied sample has not remained unaltered over time. Rather, communities of microorganisms, particularly yeasts adapted to cold conditions, have colonized and proliferated on the mummy, despite the low temperatures at the original site or in the museum. It also shows that museum conservation practices, such as spraying water to maintain humidity or applying disinfectants, have altered the microbial communities, introducing or selecting for certain organisms. The study is important because it sheds light on how to interpret microbial findings in ancient samples. It also casts doubt on studies of ancient samples that assume the sequences obtained belong to ancient microbes associated with the individual or the original environment. It reminds us that microbes, including yeasts, thrive in environments as extreme as sub-zero temperatures.

The study not only throws a bucket of cold water (literally) on our hopes of understanding ancient microbial communities; It also provides possible solutions to improve the preservation of ancient samples or to discern between the original microbial composition of an archaeological sample and subsequent colonizations.