Ancient and modern microorganisms were found together in a mummy preserved frozen in Alpine perennial snow. Some are still proliferating, indicating that new measures are needed for mummy preservation. Microorganisms adapted to low temperatures were also suggested to have industrial potential.
Researchers at the Italian private institute Eurac Research said on the 3rd in the international microbiology journal Microbiome that they found microorganisms that had coexisted in the intestines during life in the remains of the mummy Ötzi excavated from the Alps, along with microorganisms that entered from the surrounding environment after death or arose during preservation, and that some of them are still metabolically active.
Ötzi was a hunter who lived about 5,300 years ago, during the transition from the Neolithic to the Bronze Age. He was found in 1991 with an arrowhead lodged in his back in ice along a trail in the Alps. Although he was named Ötzi because he was found in the Ötztal region on the Italy-Austria border, people called him the "iceman" because he emerged from the ice.
◇ Microorganisms that coexisted with the iceman for 5,300 years
When Ötzi was excavated, Austria and Italy each claimed ownership. The site was later confirmed to be Italian territory, and the mummy is now kept at the South Tyrol Museum of Archaeology in Italy. Ötzi is preserved under the same conditions as at the time of excavation, at minus 6 Celsius and 99% humidity.
The mummy research unit at Eurac Research in South Tyrol analyzed microorganisms from the ice on Ötzi's skin and from water that melted from inside the body. It also used 2019 research data on microorganisms in intestinal tissue and stomach contents. Ötzi's microorganisms were compared with those in samples collected from the surrounding soil and ice at the time of the 1991 excavation.
The team identified genetic material from microbial communities that grow in anaerobic, oxygen-free environments, such as Clostridium, in intestinal tissue and stomach contents. They concluded these were ancient gut microorganisms because the DNA was clearly damaged and the types are rarely found in the intestines of modern people.
Four species of yeast, a fermenting microbe, were also found in the mummy. They appeared on the mummy's skin, in water melted from inside the remains, and in the stomach contents. The yeasts were adapted to cold environments like Antarctica. The researchers explained, "It is possible that yeasts living in glaciers entered Ötzi after he became a mummy and coexisted for thousands of years."
Some of the yeasts appear to have remained dormant for a long time and then multiplied again during the mummy's preservation. Yeasts of the genus Glaciozyma increased in number after 2010, while the degree of DNA damage decreased. Frank Maixner, head of the Eurac Research mummy institute, said, "The yeasts have accompanied the mummy over a long journey spanning thousands of years," adding, "This shows that a mummy is not a static artifact but a dynamic biological system."
◇ New clues for mummy preservation research
Surprisingly, the nutrient that revived the yeasts was a substance used in mummy preservation to prevent mold. Three of the four yeast species carried genes that break down phenol. Phenol is used as an antimicrobial to kill mold on the mummy's surface.
Modern microorganisms were also detected in the mummy. The museum regularly sprays water to prevent the mummy from losing moisture. The modern microorganisms identified this time were analyzed as originating from the humidity-control spray water. Preservation measures created an environment favorable to cold-tolerant, antimicrobial-resistant yeasts and modern microorganisms.
The study is expected to greatly aid future mummy preservation. Fortunately, no evidence has been observed so far that microorganisms have damaged the mummy. Elisabeth Vallazza, director at the South Tyrol Museum of Archaeology, said, "The current state of preservation of the mummy is very stable."
The Eurac Research team proposed that continued monitoring is needed because microorganisms in the mummy may awaken from dormancy and break down the remains' tissues. Director Vallazza also said, "Further research and effort are needed to preserve the mummy so that more generations can see it in the future."
The researchers said the findings not only help preserve mummies but also open the door to new research. For example, the cold-resistant microorganisms found in the mummy could be used in energy-efficient industrial processes such as low-temperature fermentation.
◇ A time capsule showing prehistoric times
The iceman Ötzi has shown how humans lived and where they moved 5,300 years ago. In other words, he has served as a kind of time capsule preserving the past. The Max Planck Institute for Evolutionary Anthropology in Germany reported in 2023 in the international journal Cell Genomics that Ötzi was a descendant of a farming group from Anatolia, now part of Türkiye, with dark skin and a bald head.
Modern Europeans are a genetic mixture of three groups. A blend of Western hunter-gatherers from 8,000 years ago and Anatolian farmers was later joined by nomads from Eastern Europe 4,900 years ago. Analysis of Ötzi's genes showed a proportion of Anatolian farmer ancestry more than 92% higher than in other early Europeans.
When Ötzi's genes were analyzed in 2012, genes from Eastern European nomadic groups were detected, but this was later found to be the result of contamination with modern DNA. That study also suggested that Ötzi was a hirsute man with light skin and eyes, but the 2023 analysis indicated it was more likely his skin and eye color were darker than expected and that he was bald.
Ötzi has also aided research into prehistoric human diseases and diets. Bread, vegetables, and venison were found in Ötzi's intestines. This is evidence that humans ate a variety of foods 5,000 years ago. Helicobacter pylori, a common gastritis bacterium in modern people, was also found in the stomach. Frank Maixner published in Science in 2016 the results of genetic analysis of this Helicobacter.
The Helicobacter pylori detected in Ötzi's stomach was closer to an Asian lineage rather than the Asia-Africa hybrid common in today's Europeans. Based on this, the researchers suggested that 5,300 years ago the modern European-type Helicobacter had not yet formed in Europe, and that later migration of populations carrying African-lineage Helicobacter may have reshaped the landscape of gastritis bacteria in Europe.
References
Mocrobiome(2026), DOI: https://doi.org/10.1186/s40168-026-02417-6
Cell Genomics(2023), DOI: https://doi.org/10.1016/j.xgen.2023.100377
Cell Host & Microbe (2019), DOI: https://doi.org/10.1016/j.chom.2019.08.018
Science(2016), DOI: https://doi.org/10.1126/science.aad2545