Bacteria are masters of survival, thriving even in the most extreme environments on Earth. A changing climate impacting these underexplored ecosystems, however, may be like opening Pandora’s box, unleashing bacteria resistant to conventional antibiotics into wider ecosystems.
To better understand what genetic bacterial diversity is hidden in ice, researchers isolated a bacterial strain from a 5,000-year-old layer of ice recovered from one of the largest ice caves in Romania, only to discover its resistance to 10 commonly used antibiotics.
Besides demonstrating the existence of potentially dangerous microorganisms currently locked in environments vulnerable to global warming, the study, published in Frontiers in Microbiology, laid out that exploring prehistoric bacteria samples preserved in ice caves might also hold the key to combating the rise of antibiotic resistance in the future.
“[The strain] can also inhibit the growth of several major antibiotic-resistant ‘superbugs’ and showed important enzymatic activities with important biotechnological potential,” said co-author Cristina Purcarea, a senior scientist at the Institute of Biology Bucharest at the Romanian Academy, in a press statement.
Antibiotic Resistance Evolution in Ancient Bacteria
Bacteria have developed ways to survive exposure to naturally occurring antibiotics throughout their evolutionary history and preserve these skills in their DNA, which can then be passed on to the next generation to ensure survival in their chosen environment.
The research team from Romania set out to study one particular bacterial strain, named Psychrobacter SC65A.3, known to have adapted to colder environments. Some species can infect humans and animals, but this strain’s antibiotic resistance behavior is still unclear.
“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,” added Purcarea.
To gather samples, the team drilled about an 82-foot (25-meter) ice core from Scărișoara Ice Cave’s “Great Hall,” which represents a 13,000-year timeline. The core was then fragmented, sorted into sterile bags to avoid contamination, and kept frozen until further analysis. In the lab, the team sequenced the genome of the isolated bacterial strain and searched for the genes that code for antimicrobial characteristics.
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Resistance to 10 Antibiotics
Researchers applied a total of 28 antibiotics commonly used in medical practice to the SC65A strain, which showed resistance to 10 drugs, including rifampicin, vancomycin, and ciprofloxacin, which “are widely used in oral and injectable therapies used to treat a range of serious bacterial infections in clinical practice,” according to Purcarea.
“The Psychrobacter SC65A.3 bacterial strain isolated from Scărișoara Ice Cave, despite its ancient origin, shows resistance to multiple modern antibiotics and carries over 100 resistance-related genes,” said Purcarea.
SC65A.3 is also the first Psychrobacter strain to show resistance to other critical antibiotics, including trimethoprim, clindamycin, and metronidazole, which treat lung, skin, blood, and reproductive system infections.
However, another important finding was SC65A.3’s ability to inhibit 14 ESKAPE-group pathogens, such as MRSA, Enterococcus faecium, Enterobacter sp., Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii, which are notorious for their multidrug resistance, especially in hospital settings.
Finding Solutions in Ancient Bacteria
Overall, the findings hint that cold-loving bacterial strains are not only a reservoir for antibiotic resistance genes threatening our health but could also hold new tools to help us combat current antibiotic resistance challenges.
“If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance,” said Purcarea. “On the other hand, they produce unique enzymes and antimicrobial compounds that could inspire new antibiotics, industrial enzymes, and other biotechnological innovations.”
During their analysis, the team found close to 600 unknown genes, providing fodder for ongoing exploration into novel biological mechanisms that could be important in the fight against the growing problem of antibiotic resistance, showing how we can tap into nature to find solutions.
“These ancient bacteria are essential for science and medicine,” Purcarea concluded, “but careful handling and safety measures in the lab are essential to mitigate the risk of uncontrolled spread.”
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