Although Ötzi the Iceman may have met his end by an arrow 5,300 years ago, his remains are still alive with microbial activity, according to researchers. Yeast strains, possibly dormant in his body for thousands of years and adapted to extreme cold, may remain metabolically active, as detailed in a new study in Microbiome.
Ötzi perished in the glacial regions of the Italian Alps, where the cold and low oxygen levels helped preserve and mummify him. Since his discovery, his body has been stored at minus six degrees Celsius (21.2 degrees Fahrenheit) with high humidity to maintain its condition. Remarkably, genetic fragments from the microbes in Ötzi’s gut also survived, due to both the natural conditions before his discovery and the preservation efforts afterward.
“This combination preserved the DNA of the mummy and also the DNA of the bacteria, the indigenous microbiome, but also the environmental DNA surrounding the mummy,” says Mohamed Sarhan, a microbiologist at Italy’s Eurac Research Institute for Mummy Studies and lead author of the new paper.
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Sarhan and his team examined the microbial and fungal communities on Ötzi’s skin, various tissues, and thawed water from within the mummy. They identified multiple anaerobic bacteria species, such as Romboutsia hominis, Clostridium moniliforme, Ruminococcus bromii, which likely aided in digesting his food. Previous research on his stomach contents and microbiome indicated that Ötzi, found by hikers in 1991, consumed a high-fat diet with dried wild meat, cereals, and even a poisonous fern. The gut microbes discovered align with this diet, as the species are well-adapted to those foods. While some of these microbes are still present in modern humans, others have become less common as diets have changed.
Eurac Research/Andrea De Giovanni
“We have two or three species that were never reported before in [Ötzi’s] case that we know already are very rarely found in modern humans,” Sarhan says. “We can still find them in some nonindustrialized societies, like some tribes in Africa or South America and also some places in Europe, but in very, very rare cases.”
Yeast samples from Ötzi’s skin, stomach, and meltwater inside his body have shown several cold-adapted species, suggesting they originated from the environment where he was found. Comparing these samples to ones from nine years earlier, researchers noted changes in the yeast populations. Some species have thrived by digesting phenol, used to disinfect the body, despite the mummy’s sub-zero storage conditions. This observation could significantly impact mummy conservation, according to Sarhan.
“This needs to be to be followed up on in the future to understand what happened during this time and also what will happen in the future,” he says. “How we can stop this…? One of the things that we don’t want to forget is that the conservation of the Iceman includes everything: the Iceman as a body but also the biomolecules, proteins, DNA, metabolites and also the internal bacteria.”
This research could not only aid in preserving Ötzi but also serve as a guide for conserving other frozen biological finds.
“The main motivation of this study was the microbiological conservation of the mummy,” Sarhan says. “We wanted to understand whether the current conditions of the preservation are good enough.”
Sarhan anticipates that as technology for sequencing and cultivating bacteria advances, further insights will emerge from Ötzi’s remains, even if the exact cause of his death remains unresolved.
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