IT IS frigid, dim, and incredibly ancient within the Scarisoara ice cave. Nestled deep within the Apuseni mountains of Romania, this underground cathedral holds a colossal ice block that has been gradually building up for more than 10,000 years. As Cristina Purcarea and her team from the Institute of Biology Bucharest meticulously lifted a 25-meter ice core from the cave’s Great Hall, they sought more than just climatic information. They were in pursuit of the “living dead”—bacteria that have been preserved in a deep freeze since the onset of human civilization.
What they uncovered has disconcerting ramifications for our future. Among the ice, the team pinpointed a strain of Psychrobacter bacteria, labeled SC65A.3, which has remained dormant for 5000 years. Although it has had no interaction with humanity’s medicinal arsenal, this ancient microbe is already resistant to 10 categories of contemporary antibiotics. “The Psychrobacter SC65A.3 bacterial strain, despite its ancient origins, exhibits resistance to several modern antibiotics,” Purcarea states.
The revelation dismantles the reassuring belief that antibiotic resistance is solely a modern “lifestyle” ailment of our own creation. Rather, it appears that the genetic templates for countering our most potent medications—including vancomycin and ciprofloxacin—were present in the natural environment long before we ever constructed a hospital. As the planet heats up and ancient ice thaws, these subterranean reservoirs of resistance could begin to circulate.
Psychrobacter are cold specialists. They inhabit permafrost, Antarctic soils, and the deep ocean. To withstand the oppressive stillness of the Scarisoara ice, SC65A.3 has developed a set of over 100 resistance-related genes. While we perceive antibiotics as medical treatments, in the microbial realm, they are frequently utilized as chemical weapons in an ongoing battle for territory and resources. “Investigating microbes like Psychrobacter SC65A.3 uncovers how antibiotic resistance developed naturally in the environment, long before modern antibiotics were utilized,” Purcarea comments.
To evaluate the strain’s resilience, the team challenged it with 28 different medications. The findings were astonishing. The bacteria dismissed rifampicin, utilized for treating tuberculosis, and vancomycin, often regarded as a last-resort drug for severe “superbug” infections. For the first time within this genus, researchers also observed resistance to trimethoprim and metronidazole, common remedies for urinary tract and respiratory infections.
This phenomenon is referred to by microbiologists as the “natural resistome”—an extensive, ancient archive of resistance genes that exists in nature. The peril is that these genes are not static. Bacteria are notoriously promiscuous, capable of exchanging DNA like collecting cards through a process known as horizontal gene transfer. If thawing ice releases these ancient specialists into contemporary ecosystems, they could convey their primal secrets to modern pathogens. “Should melting ice liberate these microbes, these genes might propagate to today’s bacteria, exacerbating the global challenge,” cautions Purcarea.
However, the news from the ice isn’t wholly grim. In a manner akin to how a poisoner must also have the antidote, SC65A.3 seems to be a prolific generator of its own antimicrobial substances. The team identified 11 genes within its genome that enable the bacteria to eliminate or limit the growth of competing “superbugs,” fungi, and even viruses.
This dualistic nature renders the cave ice a double-edged sword. While it presents a potential hazard, it is simultaneously a treasure trove for pharmaceutical seekers. The genome of SC65A.3 comprises nearly 600 genes with completely unknown roles. These might serve as the blueprints for the next generation of antibiotics or possibly industrial enzymes capable of functioning at temperatures where modern chemistry falters. “They generate unique enzymes and antimicrobial substances that could inspire new antibiotics,” asserts Purcarea.
At present, the team is approaching their discovery with utmost caution. The researchers adhere to stringent safety protocols to ensure their “time-traveling” bacteria do not escape the lab. “Diligent handling and safety precautions in the laboratory are crucial to mitigate the risk of uncontrolled spread,” Purcarea emphasizes.
The tale of SC65A.3 serves as a reminder that we are latecomers in a very ancient conflict. Our battle against infection is merely the latest segment in a multi-billion-year chemical arms race. As we persist in exploring the world’s diminishing ice, we are discovering that the past is not as concealed as we presumed. The secrets encased within the darkness of Scarisoara may aid us in enduring the “superbug” era—or they may simply reveal that our adversaries were prepared for us millennia before our arrival.
Study link: https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1713017/full
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