Researchers studying the 5,300-year-old mummy have identified a unique mixture of ancient microbes, alongside modern microorganisms that appear to have colonised the body during its conservation, as per Springer Nature.
About the preservation of copper age individual
Ötzi was naturally preserved in the low-temperature surroundings of the glacier for more than five millennia before being discovered in the Ötztal Alps. The freezing temperatures acted as a natural protective shield, preventing the body from decomposing and limiting microbial activity. His preserved remains were discovered in 1991 in the Ötztal Alps, near the present-day border between Austria and Italy.
Following the discovery, scientists treated the mummy with a special phenol-based solution to prevent fungal growth. Researchers soon realised that maintaining a frozen environment was essential for preserving the ancient remains and preventing microbial contamination.
Today, Ötzi is housed in a specially designed refrigeration chamber at the South Tyrol Museum of Archaeology in Bolzano, Italy. The chamber is kept at a constant temperature of -6°C and a humidity level of 99%, closely replicating the glacier conditions that preserved the mummy for thousands of years. The only notable difference is a slightly higher oxygen concentration compared to the glacier environment due to differences in altitude.
Uncovering ancient microbial communities
To better understand the microorganisms associated with the mummy, researchers combined multiple scientific techniques, including amplicon sequencing, metagenomics, and genome analysis. Their findings revealed three main sources of microbes: bacteria that developed naturally after death, ancient microorganisms preserved from the glacier environment, and modern microbes introduced during the mummy’s conservation.
Analysis of tissue samples uncovered several ancient gut bacteria that appear to have survived for more than 5,000 years. These microorganisms closely resemble those found in ancestral human populations and provide valuable insights into the gut ecosystem of people living during the Copper Age.
Researchers also discovered significant changes in the microorganisms living on the mummy’s exterior. Several cold-adapted yeast species, including Glaciozyma watsonii, Mrakia robertii, Phenoliferia glacialis, and Goffeauzyma, have become increasingly common over recent years.
Although the bacterial communities inside the Iceman remained largely unchanged, researchers observed a noticeable increase in certain yeast species living on the mummy’s surface between 2010 and 2019. These microorganisms showed fewer signs of ancient DNA damage, suggesting they are modern microbes that have recently colonized the mummy rather than being preserved from ancient times.
Why preservation conditions matter
One of the key questions surrounding the Iceman has been whether the current storage conditions fully stop microbial activity or simply slow it down. Although the freezing temperatures prevent the growth of most organisms responsible for decomposition, they may still allow cold-adapted microorganisms.
Scientists have questioned whether these settings might still allow cold-adapted microorganisms to remain active and potentially contribute to gradual deterioration over time.
Previous studies have detected microbial DNA inside the mummy’s tissues, but they were unable to determine whether these microorganisms were dead, dormant, or still biologically active. As a result, researchers have lacked a clear understanding of the long-term risks posed by microbial activity within the mummy’s preservation environment.
More than a static relic
The research suggests that Ötzi should not be viewed solely as a static relic. Instead, researchers describe him as a dynamic biological interface where ancient microorganisms that have survived for thousands of years coexist with modern microbes that have colonized the mummy more recently.
The presence of both ancient gut microbes and newly introduced microorganisms indicates that some microbial activity may still be occurring, even in the freezing conditions. The findings highlight the importance of maintaining strict storage conditions to protect the ancient remains.