SOUTH TYROL — An Italy-based research team has found that Oetzi the Iceman's frozen body hosts living, metabolically active microorganisms, including cold-adapted yeasts that have survived for millennia. The discovery challenges the assumption that the 5,300-year-old mummy is a biologically static relic and instead reveals it functions as a dynamic microbial ecosystem.

Scientists identified four different yeasts capable of surviving sub-zero temperatures in Oetzi's guts, skin, and melted water from his body. Genetic analysis showed DNA damage levels in the yeast comparable to microbes originally present in his digestive tract, suggesting the yeasts entered his body soon after death. Lead study author Mohamed Sarhan of the Eurac Research institute in Bolzano told AFP, "What we didn't expect to find was yeast." He added in an interview, "The cold-adapted yeasts are growing. Certain bacteria have colonized and persisted across his tissues for decades. The mummy is, in a very real sense, a living biological interface — a meeting point between the ancient world and the present, where microbes from 5,000 years ago coexist with organisms that arrived last decade."

Researchers reproduced the gut yeast in a refrigerator and used it to make sourdough bread. "Initially it didn't work," Sarhan said. "But after three months of effort we had a very, very good sourdough." Study co-author Frank Maixner said in a statement, "These yeasts have accompanied Oetzi on his long journey through the millennia." Maixner also said, "He is a visitor who provides us precious insights into the past." The yeasts demonstrated an ability to metabolize phenol, a chemical used in 1991 to prevent fungal growth on the mummy after its discovery by German hikers in South Tyrol, Italy.

Not all scientists are convinced the microbes are ancient. Nikolay Oskolkov, a researcher at the Latvian Institute of Organic Synthesis, told AFP it was interesting that "the Iceman's microbiome is not 'frozen'." However, he cautioned that yeast samples were only taken in 2010 and 2019, providing "very little evidence that the yeasts have been multiplying over millennia," and added that he believed they were "relatively recent colonists of the mummy's body." Sarhan acknowledged it is too early to determine whether the yeast is harming the mummy and called for more research.