Researchers discover antibiotics resistancy in millenia-old bacterium preserved in ice

Bacteria are renowned for surviving in some of Earth’s most extreme environments, from scorching heat to deep freezes. Ice caves are among these habitats, harboring microbial communities that scientists are only beginning to study for their genetic potential. A recent discovery in Romania has raised concern after such a bacterium preserved for millennia was found to possess resistance to modern antibiotics.

Romanian researchers analyzed a bacterial strain trapped for around 5,000 years in the ice of Scărișoara Ice Cave, an underground glacier in the Apuseni Mountains. Their findings indicate that ancient microbes can naturally carry antibiotic resistance traits, offering insight into how such resistance develops and persists over time, as an article by SciTechDaily explains.

“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, a senior scientist at the Institute of Biology Bucharest of the Romanian Academy. “But it can also inhibit the growth of several major antibiotic-resistant ‘superbugs’ and showed important enzymatic activities with important biotechnological potential.”

To conduct the study, scientists drilled a 25-meter ice core from a section of the cave known as the Great Hall, retrieving layers spanning roughly 13,000 years. Samples were sealed in sterile bags and kept frozen during transport to avoid contamination. In the laboratory, researchers isolated bacterial strains and sequenced their genomes, identifying genes linked to cold adaptation, antimicrobial resistance and antimicrobial activity.

The team tested the SC65A strain against 28 antibiotics from 10 different classes, including drugs widely used in clinical settings. Some of the antibiotics are known to be associated with specific resistance genes or mutations, enabling researchers to compare genetic data with laboratory results.

“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,” Purcarea pointed out.

Conditions such as tuberculosis, colitis and urinary tract infections are treated with some of the antibiotics to which resistance was observed, including rifampicin, vancomycin and ciprofloxacin.

Psychrobacter SC65A.3 belongs to the genus Psychrobacter, bacteria adapted to cold environments. While certain species can cause infections in humans or animals, the group is also considered promising for biotechnological applications. However, little research has examined how these cold-adapted microbes respond to antibiotics.

SC65A.3 is the first known Psychrobacter strain shown to resist antibiotics such as trimethoprim, clindamycin and metronidazole. Its resistance profile suggests that cold-environment bacteria may act as reservoirs of resistance genes — DNA segments that allow microbes to withstand antibiotic treatments.

Purcarea noted that the discovery presents both risks and opportunities. If released, such bacteria could contribute to the global antibiotic resistance challenge. At the same time, their unique enzymes and antimicrobial compounds may offer valuable leads for developing new antibiotics, industrial enzymes and other biotechnological innovations.

By Nazrin Sadigova