A Romanian research team analyzed a bacterial strain from a 5,000-year-old ice layer in Scarisoara Ice Cave, uncovering resistance to modern antibiotics and opportunities for countering resistance spread. Bacteria have evolved to endure extreme settings like ice caves, representing a source of genetic diversity has that not been extensively studied.
Psychrobacter SC65A.3, isolated from the cave ice, resists numerous current antibiotics despite its age. It possesses over 100 resistance-related genes, suppresses growth of key antibiotic-resistant superbugs, and displays enzymatic activities with biotechnological promise. “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,” explained Cristina Purcarea, senior author of the study published in Frontiers in Microbiology.
The team drilled a 25-meter ice core from the cave's Great Hall, representing a 13,000-year timeline, and kept the ice fragments frozen in sterile bags to avoid contamination. Lab work involved isolating bacterial strains and sequencing their genome to pinpoint genes for cold survival, antimicrobial resistance, and activity. Genome analysis identified resistance genes, nearly 600 genes with unknown functions, and 11 genes potentially combating other bacteria, fungi, and viruses.
Psychrobacter species thrive in cold and may infect humans or animals, but their antibiotic resistance profiles were mostly unknown. The strain withstood 10 of 28 tested antibiotics across 10 classes, including rifampicin, vancomycin, and ciprofloxacin for tuberculosis, colitis, and UTIs, plus first detections for trimethoprim, clindamycin, and metronidazole against lung, skin, blood, and reproductive infections. Purcarea pointed out: “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.”
This profile indicates cold-adapted strains could act as reservoirs for DNA sequences promoting drug survival. Purcarea cautioned: “If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance.” Conversely, they hold value: “On the other hand, they produce unique enzymes and antimicrobial compounds that could inspire new antibiotics, industrial enzymes, and other biotechnological innovations.”
Examining these ancient microbes sheds light on pre-antibiotic natural resistance evolution. Purcarea concluded: “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.”
Publication details: Paun VI, Itcus C, Lavin P, Chifiriuc MC and Purcarea C (2026) First genome sequence and functional profiling of Psychrobacter SC65A.3 preserved in 5,000-year-old cave ice: insights into ancient resistome, antimicrobial potential, and enzymatic activities. Front. Microbiol. 16:1713017. doi: 10.3389/fmicb.2025.1713017
Psychrobacter SC65A.3, isolated from the cave ice, resists numerous current antibiotics despite its age. It possesses over 100 resistance-related genes, suppresses growth of key antibiotic-resistant superbugs, and displays enzymatic activities with biotechnological promise. “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,” explained Cristina Purcarea, senior author of the study published in Frontiers in Microbiology.
The team drilled a 25-meter ice core from the cave's Great Hall, representing a 13,000-year timeline, and kept the ice fragments frozen in sterile bags to avoid contamination. Lab work involved isolating bacterial strains and sequencing their genome to pinpoint genes for cold survival, antimicrobial resistance, and activity. Genome analysis identified resistance genes, nearly 600 genes with unknown functions, and 11 genes potentially combating other bacteria, fungi, and viruses.
Psychrobacter species thrive in cold and may infect humans or animals, but their antibiotic resistance profiles were mostly unknown. The strain withstood 10 of 28 tested antibiotics across 10 classes, including rifampicin, vancomycin, and ciprofloxacin for tuberculosis, colitis, and UTIs, plus first detections for trimethoprim, clindamycin, and metronidazole against lung, skin, blood, and reproductive infections. Purcarea pointed out: “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.”
This profile indicates cold-adapted strains could act as reservoirs for DNA sequences promoting drug survival. Purcarea cautioned: “If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance.” Conversely, they hold value: “On the other hand, they produce unique enzymes and antimicrobial compounds that could inspire new antibiotics, industrial enzymes, and other biotechnological innovations.”
Examining these ancient microbes sheds light on pre-antibiotic natural resistance evolution. Purcarea concluded: “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.”
Publication details: Paun VI, Itcus C, Lavin P, Chifiriuc MC and Purcarea C (2026) First genome sequence and functional profiling of Psychrobacter SC65A.3 preserved in 5,000-year-old cave ice: insights into ancient resistome, antimicrobial potential, and enzymatic activities. Front. Microbiol. 16:1713017. doi: 10.3389/fmicb.2025.1713017