Ötzi’s frozen body may still host living microbes

Ötzi’s frozen – New analysis of Ötzi the Iceman’s preserved remains suggests some microbes lingering on his 5,300-year-old skin may still be metabolically active under conservation conditions—raising new questions about how “frozen” the mummy really is and whether conservatio

In Bolzano, Italy, Ötzi the Iceman has been kept where his discovery story began—only in a controlled room. The South Tyrol Museum of Archaeology stores the 5. 300-year-old mummy in a refrigeration chamber held at a constant temperature of -6°C and a relative humidity of 99 per cent. designed to mimic the environment of the Alpine glacier where he was found.

But a new study suggests that even those icy conservation conditions may not fully stop the microbes that hitchhiked on Ötzi’s body after he died.

Ötzi was discovered in 1991 thawing out of an Alpine glacier close to the border of Austria and Italy. Archaeologists estimate he lived between 3350 and 3120 BC. In the 35 years since his discovery. researchers have used his preserved tissues to reconstruct everything from his appearance—he was probably dark-skinned and balding—to details of his life. including numerous tattoos. Studies have also pointed to a wound in his shoulder from an arrow, suggesting he was murdered.

Now. researchers at Eurac Research’s Institute for Mummy Studies in Bolzano. led by Frank Maixner. have turned their attention to the microbes. The team analyzed bacteria and fungi from skin swabs. tissue fragments. and internal thawed water samples taken from Ötzi in 1992. 2010. and 2019. They compared those findings with soil and ice samples collected from the discovery site in the 1990s.

What they found was a layered microbial community: both ancient organisms and modern-day microbes. Maixner said the researchers could “really distinguish between the Iceman’s endogenous gut bacteria and microbes that joined from the environment as soon as he died.”

Inside Ötzi’s body. metagenomic analysis of internal tissues pointed to specialist bacteria that thrive without oxygen in the mammalian gut. including species of Treponema and Kineothrix. Crucially. the researchers used patterns of DNA damage—damage that accumulates over time—to infer that these bacteria probably lived inside Ötzi when he was alive.

The internal samples also held a wide variety of microbes, consistent with other prehistoric gut microbial communities. Maixner said this may reflect the more varied diet of Copper Age humans compared with modern Western societies.

At the same time, the team detected Pseudomonas bacteria—commonly found in soil and water—in all samples. DNA damage suggested these bacteria likely belonged to an ancient community from the discovery site.

Outside Ötzi, on external samples, the picture was different again. The researchers uncovered cold-loving, or psychrophilic, yeasts, including Phenoliferia, Glaciozyma, Goffeauzyma, and Mrakia. DNA damage indicated these yeasts were also ancient, but one species stood out. The abundance of Glaciozyma rose between 2010 and 2019, eventually becoming the dominant strain, while DNA damage levels dropped.

For the researchers, the shift was hard to ignore. Nikolay Oskolkov at Lund University in Sweden said the findings offer “good evidence that Glaciozyma colonised the mummy post mortem. ” adding that the yeasts “seem to be growing for some reason.” He also cautioned that more data points are needed to rule out the possibility that results reflect experimental procedure.

Others emphasized how activation is not the same as growth. Damla Kaptan at the University of Stavanger in Norway said the trend is “potentially very interesting. ” but she stressed that activity can’t be confirmed without seeing RNA produced by the yeast—evidence that genes are turned on. She also noted that there is still a possibility that the yeast remained dormant or became active during thawing.

Some of the yeasts also carry genes for breaking down protein and collagen, which could, in theory, harm the mummy. Yet the team reported no evidence of damage.

What may worry conservators is that these microbes could be responding to the very efforts used to preserve Ötzi. The study found that some microbes contain genes required for degrading the toxic compound phenol. Maixner suggested this may be a side effect of treatments researchers used in the 1990s to kill off fungi. When Ötzi was found, there was already active mould formation, and he was treated with a phenol-containing substance, Maixner said. “Perhaps the microbiome was enriched by the treatment.”.

Taken together, the findings challenge the idea of Ötzi as a perfectly sealed relic—an unchanging specimen trapped in ice. Maixner said the study shows that Ötzi is not a biologically frozen time capsule. but a complex ecosystem shaped by the succession of his gut microbes after he died. by organisms infiltrating from the glacier over thousands of years. and then by three decades of conservation.

The question now is what that means for the future of the mummy. Maixner asked whether microorganisms that have been on the mummy since the beginning should be considered part of the remains. He recommended regular genomic surveillance. including looking for signs of activity like RNA and metabolites produced by microbes. to determine whether the microbial communities have truly “awoken” from dormancy and are degrading Ötzi’s tissues.

If they are active, the implications could reach beyond one artifact. The team said scientists might need to consider whether conservation conditions should be changed—perhaps by lowering the temperature or humidity—to further restrict microbial activity.

Ötzi the Iceman microbes metabolically active microbes Glaciozyma psychrophilic yeasts metagenomic analysis mummy conservation South Tyrol Museum of Archaeology Eurac Research