A new study untangles the complex microbial history of Ötzi the Iceman, revealing which microorganisms originated during his lifetime and which arrived long after his death.
For more than 5,000 years, Ötzi the Iceman has carried an invisible community of microbes through ice, time, and modern museum preservation. Now, scientists have taken the most detailed look yet at this microbial ecosystem, separating the microorganisms that accompanied Ötzi in life from those that arrived after his death and during decades of conservation.
By analyzing a wide range of samples with multiple genetic and microbiological techniques, the researchers identified traces of bacteria from Ötzi’s original gut microbiome in internal tissues. They also uncovered an unexpected group of cold-adapted yeasts that likely originated in the glacier environment and have remained associated with the mummy to this day.
The findings, published in the journal Microbiome, offer new insights into the long-term preservation of ancient remains and the remarkable survival strategies of microorganisms in extreme cold.
The investigation was extensive. Researchers analyzed surface ice, meltwater collected from inside the mummy, and numerous swab samples. They also incorporated data from earlier studies of intestinal tissue and stomach contents. To better understand environmental influences, the team examined a soil sample from the discovery site that had been collected and frozen during Ötzi’s recovery in 1991.
The scientists also found genetic traces of the original gut microbiome in intestinal tissue and stomach contents. First described in a 2019 study conducted with Eurac Research, this microbial community closely resembles the limited examples of gut bacteria known from early human populations. Such microbes are rarely found in people living in modern industrialized societies, making Ötzi an unusually valuable source of information about the human microbiome of the past.
Cold-Adapted Yeasts Linked to Glacier Environment
The newly identified yeasts were recovered from skin samples, meltwater inside the mummy, and stomach contents. These highly specialized organisms are adapted to cold conditions. Genetic testing showed they are related to strains found in extremely cold regions, including Antarctica. This suggests the yeasts originated in the glacier environment and may have remained associated with the mummy for thousands of years. Researchers identified both heavily degraded (ancient) and well-preserved (modern) DNA.
The findings suggest these microorganisms are not simply remnants of the distant past. They appear to persist under current preservation conditions of minus 6 degrees Celsius (21.2 degrees Fahrenheit) and high humidity, possibly in a dormant state. “We see continuity here,” said Frank Maixner, director of the Institute for Mummy Studies at Eurac Research. “These yeasts have accompanied Ötzi on his long journey through the millennia.” According to Maixner, the results indicate that the mummy is “not a static relic, but a dynamic biological system.”
The study also indicates that earlier preservation treatments may have unintentionally encouraged the growth of certain microorganisms. Three of the four yeast species possess genes that allow them to break down phenol, a substance applied after Ötzi’s recovery to remove fungal growth from the mummy’s surface. The yeasts may have used it as a food source.
“A mummy’s microbiome is unique because we are dealing with microbes that are over 5,000 years old and, at the same time, with modern microbes that have been introduced since the discovery,” says microbiologist and lead author Mohamed S. Sarhan.
Implications for Preservation and Future Research
“The mummy’s conservation conditions are very stable today,” comments Elisabeth Vallazza, director of the South Tyrol Museum of Archaeology, which oversees the mummy’s conservation. “Close microbiological monitoring ensures that the mummy suffers no damage. But further research and full conservation efforts are certainly needed to preserve it for many more generations.”
Conservation expert and coauthor Marco Samadelli emphasized, “The conditions under which glacial mummies are preserved are not yet fully understood. This study expands our knowledge in this area.”
Beyond improving preservation efforts, the findings may also have practical applications. Cold-adapted microorganisms could potentially be used in energy-efficient industrial processes, including low-temperature fermentation.
Reference: “The Iceman’s microbiome: unveiling millennia of microbial diversity and continuity” by Mohamed S. Sarhan, Marco Samadelli, Albert Zink and Frank Maixner, 3 June 2026, Microbiome.
DOI: 10.1186/s40168-026-02417-6
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