Famed Iceman, Otzi, Has Non-Human DNA: New Analysis Reveals Bacteria

Much of what we know about the specimen Otzi, the famed "Iceman" that lived thousands of years ago and was preserved as a mummy in a glacier, stems from a tiny bone sample that allowed researchers to decode his genetic makeup. Now, scientists have examined this sample a bit more closely and have found that some of it consists of non-human DNA.

"What is new is that we did not carry out a directed DNA analysis but rather investigated the whole spectrum of DNA to better understand which organisms are in this sample and what is their potential function," said Frank Maixner from the EURAC Institute for Mummies and the Iceman in Bozen/Bolzano as he described the new approach scientists are taking.

The researchers detected a sizeable presence of a particular bacterium in the DNA mixture. The bacterium itself is Treponema denticola, which is an opportunistic pathogen involved in the development of periodontitis. This latest finding supports an earlier diagnosis that Oetzi probably suffered from periodontitis.

"This 'non-human' DNA mostly derives from bacteria normally living on and within our body. Only the interplay between certain bacteria or an imbalance within this bacterial community might cause certain diseases," said Thomas Rattei of the University of Vienna. "Therefore it is highly important to reconstruct and understand the bacterial community composition by analyzing this DNA mixture."

The opportunistic pathogen wasn't the only bacteria that the researchers found, though. They also detected Clostridia-like bacteria in the sample. Currently, these bacteria are in a dormant state, but under hermetically sealed, anaerobic conditions they could become active again and degrade tissue. This finding could greatly help with the future preservation of the world-famous mummy.

"This finding indicates that altered conditions for preserving the glacier mummy, for example when changing to a nitrogen-based atmosphere commonly used for objects of cultural value, will require additional micro-biological monitoring," stated the researchers.

The findings are published in the journal PLOS One.