Recovered from the ice of an Alpine glacier at the end of the last century, almost everything was known about Ötzi. That he was about 45 years old when he was killed from behind about 5,300 years ago. A deep genetic study revealed three years ago that, besides being bald, he had dark skin and probably came from distant Anatolia. It is even known what he ate shortly before being killed by an arrow. Now, a new investigation identifies the microscopic life he carried inside. The work, published in the specialized journal Microbiome, shows that his bacteria were very different from those of humans in modern societies. They have also discovered that a series of cold-adapted fungi have awakened thousands of years later and could compromise the future of the mummy.
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“We have identified ancestral gut bacteria preserved in Ötzi that are extremely rare in people living modern and industrialized lifestyles, although they can still be found in people with traditional and non-industrialized lifestyles,” says Frank Maixner, director of the Mummy Studies Institute at the Eurac Research institution (Bolzano, Italy) and senior author of the research. “These microbes provide us with a unique and valuable picture of what the human gut was like in the Copper Age, before industrialization transformed our microbiota,” Maixner adds in an email.
The researchers took advantage of the rare opportunity they had in 2019 when, for five hours, Ötzi was thawed for a series of works with the mummy. During that time, they took samples of his skin and connective tissue, also used about ten swabs on as many parts of his body, collected some of the thawed water from inside him, reanalyzed the soil preserved since 1991 from where the mummy was extracted. They even studied the air in the chamber where the Iceman is kept, always at the same temperature (-6º) and 99% humidity, which seeks to replicate the conditions in which he was maintained for millennia.
Ötzi’s intestinal microbiome found now is the same as he had when he died. Added to this are species typical of a post-mortem process. They found a large number and variety of the genus Clostridia, already detected in some Egyptian mummies. Both in the soil and in the thawed water, they found microorganisms well adapted to the cold. In particular, they identified four species of fungi, all from the yeast group, such as Glaciozyma watsonii or Phenoliferia glacialis, whose name already gives clues: these are psychrophilic microbes, accustomed to icy environments. Some of them had already been found far from there, such as the Russian Arctic or Antarctica.
The intriguing thing about these yeasts is that, despite accompanying Ötzi in his death, some of the samples showed reduced damage to their DNA. This would indicate that at least some of those found on the Iceman’s skin were active when studied. Furthermore, by comparing them with those obtained back in 2010, they have confirmed that they have not remained still, that the microbial ecosystem of the mummy did not freeze 5,300 years ago. This leads the authors to write in their conclusions: “The crucial question now is whether these yeasts are descendants of ancient yeasts that maintained their multiplication over the years, or if they were in a latent state that reactivated after thawing the mummy.”
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According to Maixner, “here we see continuity. These yeasts have accompanied Ötzi on his long journey through the millennia.” For him, this would demonstrate that the mummy “is not a static relic, but a dynamic biological system.” But also that it may be in danger. When they extracted it from the ice, they used a chemical compound (phenol or carbolic acid) to decontaminate it. But, as happens in the fight between antibiotics and bacteria, this stopped the proliferation of some microorganisms but may have left the door open to the action of others, such as these yeasts that thrive on the Iceman’s skin.
“The preservation conditions of the mummy are very stable nowadays,” says Elisabeth Vallazza, director of the South Tyrol Archaeological Museum, which oversees its conservation. “Exhaustive microbiological control ensures that the mummy suffers no damage. However, more research and comprehensive conservation efforts are undoubtedly needed to preserve it for many more generations,” she adds in a statement.
But the study’s authors are clear that it is no longer enough to keep Ötzi at -6º and a relative air humidity of 99% to freeze the activity of his microbiome. “Our genomic analysis revealed that several of the microbes present — including some cold-adapted yeasts and certain bacteria — carry genes that encode enzymes capable of breaking down proteins, fats, and even collagen, a key structural component of skin and connective tissue,” highlights Maixner, who concludes: “this implies a latent biological risk to the integrity of the mummy in the long term.”
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