La Jornada: Scientists find yeast in the bowels of a Bronze Age mummy

Paris. In the intestines of a frozen mummy called Ötzidiscovered in the Alps in 1991, scientists found that yeast had developed… with which they made bread.

This Bronze Age man, known as the Snowman and who died from an arrow in the back 5,300 years ago, had a very unusual natural mummification process: his cells, literally frozen, retained their moisture.

The body, discovered by hikers on September 19, 1991 in a glacier on the border between Italy and Austria, is so well preserved that since then it has been a mine of information for researchers.

His remains, preserved in the museum in Bolzano (Italy), are kept at the same temperature (-6 degrees Celsius) as where they were found.

These conditions did not prevent microorganisms – both ancient and recent – ​​from remaining active in the frozen body, according to a study published Wednesday in the journal Microbiome.

“What we did not expect was to find yeast,” Mohamed Sarhan, main author of the study and researcher at the Eurac Research institute in Bolzano, tells AFP.

A “very good” sourdough

Scientists discovered four different types of yeast capable of surviving sub-zero temperatures in the intestines of Ötzion its skin and in a brownish water from the partial thawing of the mummy.

These microscopic fungi only live in very cold environments, such as Antarctica or the Alps.

Genetic analysis revealed “levels of DNA damage very comparable to those of the original microbes” present in the Iceman’s intestines, suggesting that the yeast entered there shortly after his death, Sarhan explains.

“These yeasts accompanied Ötzi on its long journey through the millennia,” says Frank Maixner, co-author of the study, in a statement.

The scientists then reproduced these mushrooms in a refrigerator.

“When you say you have yeast, they immediately ask you: can it be used to make bread?” says Sarhan.

And that was precisely what the team did.

“At first, it didn’t work,” says the microbiologist. But after three months of trying, “we got a really good sourdough starter,” he says, adding that the team is now considering brewing beer.

The study also mentions other more serious purposes for these microorganisms.

When the mummy was discovered, it was initially treated as a normal corpse, with a chemical, phenol, used to prevent fungal growth.

But the yeast was able to degrade the phenol. That is why scientists believe that, in the future, it could be used to decompose this chemical in contaminated environments.

Fibers and whole grains

This fungus was not the only surprising discovery in the body of Ötzi.

An analysis of its microbiota revealed the presence of an intestinal bacteria almost non-existent in modern humans. Although it disappeared from the stomachs of the populations of industrialized countries, it has been detected in some tribes in Africa and South America.

It was also found in 3,000-year-old excrement preserved in a salt mine in Hallstatt (Austria), one of the few other sources that allow us to observe the ancient human microbiota.

Ötzi and these Bronze Age salt miners consumed more fiber and grains than modern humans, Sarhan notes.

The study concludes that “the Iceman is not a biologically ‘frozen’ time capsule but rather a complex ecosystem.”

Nikolay Oskolkov, a researcher at the Latvian Institute of Organic Synthesis who was not involved in the study, explains to Afp ​​that it is interesting to note that “the iceman’s microbiota is not ‘frozen’.”

But the researcher, who had previously discovered fungi in the mummy’s intestines, points out that the yeast samples were only taken in 2010 and 2019.

This represents “very little evidence that yeasts have multiplied over the millennia,” he considers, estimating that they are “relatively recent elements of the mummy’s body.”