Ancient Gut Bacteria and Potentially Active Collagen-eating Fungi Both Identified in Ötzi the Iceman

Researchers have identified bacteria that lived inside Ötzi the Iceman when he was alive and cold-tolerant fungi that colonised his body after death. Frank Maixner at Eurac Research’s Institute for Mummy Studies in Bolzano and colleagues analysed skin swabs, tissue fragments and internal thawed water samples taken from the mummy in 1992, 2010 and 2019.

They compared these with soil and ice samples collected from the discovery site in the 1990s.

The team’s metagenomic analysis of internal tissues revealed specialist bacteria that thrive without oxygen inside the mammalian gut, including species of Treponema and Kineothrix. Based on the level of damage to the DNA of these bacteria, the researchers concluded they probably lived inside Ötzi when he was alive. Pseudomonas bacteria were found in all samples.

The DNA damage of these bacteria indicates they probably belong to an ancient community from the discovery site. On external samples, the team uncovered cold-loving yeasts including Phenoliferia, Glaciozyma, Goffeauzyma and Mrakia. DNA damage indicated these were also ancient microbes.

The abundance of Glaciozyma increased between 2010 and 2019 and became the dominant strain, while the level of DNA damage dropped. This suggests the yeast may be metabolically active or able to replicate under the conservation conditions. Some of the yeasts encode enzymes for breaking down protein and collagen.

The team saw no evidence of damage to the mummy. Some of the microbes contain genes required for degrading the toxic compound phenol. Researchers in the 1990s treated the mummy with a phenol-containing substance to kill off fungi after active mould formation was observed when Ötzi was found.