HQ Team
March 15, 2026: A 13,000-year-old ice cave, located in Romania’s northwestern Apuseni mountains of Transylvania, is housing bacteria that are resistant to about 10 modern antibiotics used to treat tuberculosis and urinary tract infections, a study finds.
The cave, the size of seven football fields, is acting as a deep freezer, preserving these thawed bacteria dating back 5,000 years. It could help make new antibiotics, the study authors stated.
Dr Cristina Purcarea at the Department of Microbiology at the Institute of Biology Bucharest and colleagues drilled a 25-metre cylindrical core from an area of the cave known as the Great Hall, representing a 13,000-year timeline.
To avoid contamination, the ice fragments taken from the core were placed in sterile bags and kept frozen on their way back to the lab. There, the researchers isolated various bacterial strains and sequenced their genomes to determine which genes allow the strains to survive in low temperatures and which confer antimicrobial resistance and activity.
One particular bacterial strain stood out.
Antibiotic-resistant
“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,” said author Dr Cristina Purcarea. The Scarisoara Ice Cave is one of the largest underground glaciers in Europe, located in the Apuseni Nature Park.
“But it can also inhibit the growth of several major antibiotic-resistant ‘superbugs’ and shows important enzymatic activities with important biotechnological potential.”
Psychrobacter SC65A.3 is a strain of the genus Psychrobacter, which are bacteria adapted to cold environments. Some species can cause infections in humans or animals.
These bacteria have biotechnological potential, but the antibiotic resistance profiles of these bacteria are largely unknown. “Studying microbes such as Psychrobacter SC65A.3 retrieved from millennia-old cave ice deposits reveals how antibiotic resistance evolved naturally in the environment, long before modern antibiotics were ever used,” said Purcarea.
Endocarditis
They found that Psychrobacter SC65A.3 was resistant to ten antibiotics, including rifampicin (used to treat tuberculosis), ciprofloxacin (pneumonia, urinary tract infections), and vancomycin (MRSA and endocarditis).
This could aid the fight against antimicrobial-resistant superbugs that are already threatening millions of lives. The World Health Organization’s 2025 global resistance report revealed that by 2023, one in six common bacterial infections was already untreatable.
A Lancet study estimated that resistant superbugs could kill 39 million people by 2050.
Bacteria can live in extreme temperatures, from boiling-hot temperatures of 100°C to subzero temperatures. The Psychrobacter species found in the Romanian study has also been found in Antarctic sea ice and permafrost.
Microbes have been exchanging genetic material for thousands of years, and through the process of evolution, they face selective pressures that favour survival.
Cold environments
As a result, genes that confer resistance to environmental threats, including potential antimicrobial agents, have historically been more likely to persist and proliferate. This explains how 5,000-year-old bacteria that had never been exposed to modern antibiotics could be resistant to them.
The researchers found nearly 600 genes in the Psychobacter genome with unknown functions, and at least 11 genes that could kill or stop the growth of other bacteria, fungi and viruses.
One explanation, according to the researchers, might be that bacterial strains capable of surviving extremely cold environments have adaptations such as thicker cell walls that help them resist antibiotics.
Global warming could mean that microbes like this are released into the environment, say the researchers. Bacterial strains like the one examined here hold both a threat and a promise. “If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance,” Purcarea said.
The bacteria carry enormous promise, Purcarea said. “They produce unique enzymes and antimicrobial compounds that could inspire new antibiotics, industrial enzymes and other biotechnological innovations.”
“These ancient bacteria are essential for science and medicine.”
The study was published in Frontiers in Microbiology.
