Contents of 5,300-year-old Ötzi the Iceman’s body revealed

By Stephen Beech

The microbial contents of a 5,300-year-old human's body have been revealed in unprecedented detail.

A mummified body — dubbed Ötzi the Iceman — was found by German tourist Helmut Simon on a glacier in the Tirolean Ötztal Alps, on the Italian-Austrian border, in September 1991.

Previous research has shown that he was dark-skinned and bald.

Radiocarbon-dated to 3300 BC, the body is that of a man aged 25 to 35 who was about 5 feet 2 inches (1.6 meters) tall and had weighed around 110 pounds (50 kilos).

It was originally believed that Ötzi, who is older than the Egyptian pyramids and Stonehenge, had fallen victim to exposure or exhaustion while crossing the Alps and froze to death.

But X-ray examination in 2001 showed that an arrowhead was lodged in his left shoulder, suggesting that he had likely bled to death.

Ötzi's mummy is preserved in a refrigeration chamber at a constant temperature of -6°C and a relative humidity of 99% at the South Tyrol Museum of Archaeology in Bolzano, Italy.

Now scientists at Eurac Research in Italy have obtained a detailed picture of the microbial community associated with Ötzi.

They say their findings provide insights into a complex microbiome, ranging from the gut flora of a Copper Age human to cold-adapted yeasts.

Using a range of samples and methods, the research team was able to differentiate which microorganisms were already present in the body during his lifetime and which only colonized it after his death — both during the time in the glacier and over three decades of preservation.

In samples of internal tissue, the researchers were able to detect genetic material from bacteria belonging to Ötzi's original gut flora.

A surprising discovery was the presence of cold-adapted yeast species, likely originating from the glacial environment, that have persisted on Ötzi's body to the present day.

The cold-tolerant yeasts may also hold potential for industrial applications, according to the findings published in the journal Microbiome.

The research team analyzed ice from the surface as well as meltwater from inside the mummy and collected numerous samples by swab.

Data from intestinal tissue and stomach contents were available from previous studies.

A soil sample from the discovery site, collected and frozen during Ötzi's recovery in 1991, was also analyzed to trace environmental influences.

Researchers also identified genetic material from the original gut microbiome in the intestinal tract and stomach content.

The microbiome, first described in a 2019 study conducted with Eurac Research, closely resembles the few known examples of gut flora from early human populations.

Such bacteria are rarely found in the intestines of modern humans living in industrialized societies, so Ötzi offers a rare glimpse into humanity's microbial past.

The newly discovered yeasts were isolated from skin samples, meltwater from inside the mummy, and samples of stomach content.

Such highly specialized species have adapted to cold temperatures.

Genetic analysis revealed a relationship with strains from extremely cold regions such as Antarctica.

That suggests that the yeasts originate from the glacial environment and may have been associated with the mummy for thousands of years, according to the research team.

They found both heavily degraded and well-preserved DNA.

The researchers say that indicates that the microorganisms are not merely relics of the past but continue to exist under today's preservation conditions at minus six degrees Celsius and with high humidity — possibly in a dormant state.

Frank Maixner, director of the Institute for Mummy Studies at Eurac Research, said: "We see continuity here.

"These yeasts have accompanied Ötzi on his long journey through the millennia."

He says that shows that the mummy is "not a static relic, but a dynamic biological system."

The study also shows that earlier conservation measures may have unintentionally favored certain microorganisms.

Three of the four yeasts possess the genetic capacity to break down phenol — an active ingredient used after Ötzi's recovery to rid the mummy's surface of fungal growth which the yeasts may have been able to use as a food source.

Study lead author Mohamed Sarhan said: "A mummy's microbiome is unique because we are dealing with microbes that are over 5,000 years old and, at the same time, with modern microbes that have been introduced since the discovery."

Elisabeth Vallazza, director of the South Tyrol Museum of Archaeology, said: "The mummy's conservation conditions are very stable today.

"Close microbiological monitoring ensures that the mummy suffers no damage.

"But further research and full conservation efforts are certainly needed to preserve it for many more generations."

Conservation expert and co-author Marco Samadelli added: "The conditions under which glacial mummies are preserved are not yet fully understood.

"This study expands our knowledge in this area."

The team say the findings also open new avenues for research as, for example, cold-adapted microorganisms could be used in energy-efficient industrial processes, such as low-temperature fermentation.