A team of Romanian researchers has identified a bacterium preserved for roughly 5,000 years inside an underground ice deposit that can already withstand multiple modern antibiotics. The organism, recovered from Scărișoara Ice Cave in north-west Romania, survived frozen conditions for millennia yet showed resistance to drugs routinely used today to treat infections of the lungs, skin, blood and urinary tract. The study, recently published inFrontiers in Microbiologywarns of both the potential risks and scientific value of organisms exposed as warming temperatures reach long-sealed environments, including areas covered by permanent ice such as glaciers, ice sheets, and ice caps, which together cover approximately 10% of the Earth’s land surface.
A microbe preserved in ice
To retrieve this strain, the research team drilled a 25-metre ice core from the cave’s “Great Hall”, representing about 13,000 years of accumulated ice. To avoid contamination, fragments were placed in sterile bags and transported frozen to the laboratory, where multiple bacterial strains were isolated and sequenced.
Researchers drilled a 25-meter ice core from Scărișoara Ice Cave’s Great Hall to isolate microbes/ Daily mail
The most notable organism identified was Psychrobacter SC65A.3, a cold-adapted bacterium belonging to a genus previously associated with infections in humans and animals.“The Psychrobacter SC65A.3 bacterial strain isolated from Scarisoara Ice Cave, despite its ancient origin, shows resistance to multiple modern antibiotics and carries over 100 resistance-related genes,” Dr Purcarea said.
Circular representation of the complete genome of Psychrobacter sp. SC65A.3. From the outermost to the innermost rings/ Frontiers
Genetic analysis showed the strain carries more than 100 resistance-related genes. When researchers tested it against 28 antibiotics from 10 classes routinely used in human medicine, the bacterium proved resistant to 10 of them, including drugs used to treat infections of the lungs, skin, blood, reproductive system and urinary tract such as trimethoprim, clindamycin and metronidazole.“The 10 antibiotics we found resistance to are widely used in oral and injectable therapies used to treat a range of serious bacterial infections in clinical practice,” said Dr Purcarea.The findings also clarify a broader point about resistance itself.“Studying microbes such as Psychrobacter SC65A.3, retrieved from millennium-old cave ice deposits, reveals how antibiotic resistance evolved naturally in the environment, long before modern antibiotics were ever used.”
Why the discovery matters, risk and benefit
Researchers emphasize that ancient microbes do not automatically translate into a coming pandemic, but they do represent genetic reservoirs. If thawing environments release them, their resistance traits could transfer to contemporary bacteria.“If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance,” Dr Purcarea explained.Antibiotic resistance is already widely linked to overuse of antibiotics, which reduces their effectiveness over time. The new findings indicate some resistance mechanisms did not originate in hospitals or agriculture but were present in nature long before human medicine.Scientists note that warming climates increase the chance of exposure to long-frozen organisms. A frequently cited example occurred in 2016, when a Siberian heatwave thawed permafrost and exposed an infected reindeer carcass, triggering an anthrax outbreak that killed a child and infected at least seven people, the region’s previous outbreak having occurred in 1941.
A possible medical resource, not just a hazard
The same genome that carries resistance traits also contains unexplored biology. Researchers identified 11 genes capable of killing or inhibiting bacteria, fungi and viruses, along with nearly 600 genes whose functions remain unknown.According to the study, cold-adapted strains may act as reservoirs of antimicrobial compounds and enzymes.“On the other hand, they produce unique enzymes and antimicrobial compounds that could inspire new antibiotics, industrial enzymes, and other biotechnological innovations,” said Dr Purcarea.She added that the organisms themselves are scientifically valuable but must be handled carefully:“These ancient bacteria are essential for science and medicine, but careful handling and safety measures in the lab are essential to mitigate the risk of uncontrolled spread.”
