Cold-adapted yeasts are colonising the Iceman’s body

Ötzi died in the Alps about 5,300 years ago, but his microbiome is not a frozen capsule of one moment. The body lay in ice and, after recovery, was transported, examined and stored in a cold chamber. Every stage could leave its own microbial trace. The central task of the 2026 study was therefore to distinguish ancient sequences from modern colonisation.

Some bacteria in internal tissues carried damage signatures consistent with old DNA. The surface yeasts told a different story. Four cold-adapted strains were cultured from external samples: Glaciozyma watsonii, Mrakia robertii, Phenoliferia glacialis and Goffeauzyma sp. Their relative abundance increased between sampling in 2010 and 2019, while their DNA showed weaker ancient-damage patterns.

The authors interpret these yeasts as active, modern colonisers of cold-storage conditions, not organisms demonstrated to have survived on the body since its time in the glacier. Relatedness to strains from cold environments describes their ecology; it does not date when they reached the mummy.

That distinction matters for conservation. An ice mummy is not microbiologically inert: temperature and humidity can select organisms able to grow on tissue. Monitoring change through time is therefore part of preserving the body, not merely reconstructing its past.

Correction after checking the primary paper — 29 August 2026

The study published on 3 June 2026 separates the ancient signal in some bacteria from modern yeast colonisation. The earlier “glacier yeasts” wording was too strong and has been replaced. Nor does the paper demonstrate a biotechnological application for these isolates; cold-active enzymes remain a direction for later research rather than a result of this experiment.

Three signals that separate the timelines

The modern-colonisation interpretation does not rest on the discovery of a cold-adapted species alone. The authors combine three independent observations:

1. viable yeasts were cultured mainly from surface samples, the zone exposed to contact after recovery;
2. their relative abundance increased between the 2010 and 2019 sampling series;
3. yeast sequences showed a weaker ancient-DNA damage pattern than some bacteria from inside the body.

Each line on its own has alternative explanations, but together they point to organisms functioning in the present cold-room environment. The study does not identify the day or route of first colonisation. For conservation, the measurable trend matters more: repeated sampling at the same sites can test whether a change in temperature, humidity or procedure limits growth without pretending that every microbe belongs to the mummy's ancient microbiome.

“More” means a larger share of the sample

An increase in relative abundance is not a direct count of cells across the entire body. It means that sequences from a yeast formed a larger share of the material detected in the compared samples. That share can rise because the yeast increases or because other microorganisms decline. The authors therefore interpret proportions together with viable cultures, sampling location and DNA-damage patterns.

The strongest evidence is the trend across several signals, not one percentage. A future series needs to preserve the same sampling sites and protocol so that a difference between years is not merely a change in how the mummy was sampled.