Ötzi’s Inner Ecosystem: What 5,300 Years of Microbial Life Looks Like

In the spring of 2019, researchers at Eurac Research’s Institute for Mummy Studies in Bolzano thawed Ötzi the Iceman. Not for the first time, and not to study his bones or his stomach contents or his well-documented cardiovascular disease. They thawed him to swab him. They wanted to know who else was living there.

What they found reframes what the mummy actually is. Not a preserved body. Not a static relic. A dynamic biological system, with layers of microbial community laid down across five millennia, some from before he died, some from the glacier that swallowed him, and some introduced in the decades since his discovery in 1991. Disentangling those layers is the project, and a new study published in Microbiome¹ by Mohamed Sarhan, Marco Samadelli, Albert Zink, and Frank Maixner represents the most thorough attempt yet.

The Iceman mummy is preserved in a refrigeration chamber at a constant temperature of -6° C and a relative humidity of 99%. Credit: South Tyrol Museum of Archaeology / Eurac Research/Marion Lafogler

The team’s approach was comprehensive in a way that previous work on Ötzi’s microbiome hadn’t been. They collected external ice blocks from his body before defrosting, meltwater from inside the mummy, swabs from twelve anatomical sites, soft tissue fragments, and a soil sample collected and frozen at the original discovery site during the 1991 excavation. They ran amplicon sequencing, shotgun metagenomics, and cultured organisms from the samples directly. Crucially, they compared samples taken across different years, 1992, 2010, and 2019, to look for changes over time. The goal was not just to catalog what’s there, but to figure out when it arrived.

The first thing the analysis confirmed is that Ötzi’s interior and exterior harbor fundamentally different microbial worlds. External swabs and environmental samples cluster together statistically, dominated by genera like Pseudomonas, Staphylococcus, and Acinetobacter as well as a striking abundance of Methylobacterium, which the team traced directly to the UV-treated spray water used to keep the mummy humidified. That spray water, it turns out, is dominated almost entirely by Methylobacterium and Caulobacter. Since 2010, it has been quietly reshaping what lives on Ötzi’s skin. The external microbiome you see today is, in large part, a reflection of the museum’s own plumbing.

The video shows microbiologist Mohamed Sarhan cultivating and examining colonies of a yeast strain isolated from a sample of Ötzi's stomach. Credit: Eurac Research / Andrea De Giovanni

Internal tissues tell a different story.