Laboratory tests of defrosted strains of 5,000-year-old ancient bacteria recovered from the Scarisoara Ice Cave in Romania revealed one strain resistant to several modern antibiotics used to treat a wide range of infections.
Although the ancient samples of the resistant strain, dubbed Psychrobacter SC65A.3, were retrieved from a frozen ice deposit deep in a Romanian cave, the research team behind the discovery said there is a real threat that melting ice could lead to these infectious organisms entering the modern environment, where they could pass along some of their antibiotic resistance genes to modern-day bacteria.
The 5,000-year-old strains also showed the ability to inhibit the growth of other antibiotic-resistant bacteria, suggesting their genetic profiles could be used to develop therapies to combat modern, drug-resistant strains and offer new insights into how antibiotic resistance spreads.
“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 Dr. Cristina Purcarea, a senior scientist at the Institute of Biology Bucharest of the Romanian Academy and a senior author of the study detailing the discovery.
Paun V.I.
5,000-Year-Old Ancient Bacteria Retrieved from Deep Inside an Ice Cave
According to a statement, Dr. Purcarea and colleagues drilled a 25-meter ice core into the frozen floor of a section of the ice cave known as the Great Hall. Collecting samples from this depth enabled the team to study ice deposited over the past 13,000 years.
Next, the team placed the ice core samples in labeled, sterile bags to avoid contamination. While remaining frozen, the ice core samples were transported back to the lab for examination.
During their initial analysis, the researchers isolated various bacterial strains and sequenced their individual genomes. Along with revealing the genetic identity of each strain, the research team said sequencing the genomes of bacteria that survive in these extreme climates also helped identify which genes confer low-temperature survivability.
During this process, the team identified the presence of Psychrobacter SC65A.3, a bacterial genus known for its adaptation to cold environments. Notably, some Psychrobacter strains cause infections in animals and humans.
Ancient Psychrobacter Strain Demonstrates Resistance to 10 Modern Antibiotics
In a series of tests designed to measure the resistance of the SC65A strain to commonly used modern-day antibiotics, the team selected 28 antibiotics from 10 classes used to treat bacterial infections. According to the team, several of those antibiotics “have previously been identified to possess resistance genes or mutations that give them the ability to resist drug effects.”
After running a series of tests using the Psychrobacter strains collected from the Romanian Ice cave, the team found that the ancient bacteria appeared to successfully resist 10 of the 28 tested modern-day antibiotics. This data was consistent with the genetic analysis, which identified several genes associated with antibiotic resistance.
“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,” Purcarea explained.
The researcher also noted that the 10 antibiotics are widely used “to treat a range of serious bacterial infections in clinical practice.” For example, the tests revealed resistance to rifampicin, vancomycin, and ciprofloxacin, which are used to treat diseases such as tuberculosis, colitis, and UTIs.
The ancient, 5,000-year-old bacteria also showed resistance to trimethoprim, clindamycin, and metronidazole, which are used to treat infections of the lungs, skin, or blood, and the reproductive system. The researchers note that SC65A.3 is the first Psychrobacter strain to show resistance to these three antibiotics.
If Melting Ice Releases These Microbes, These Genes Could Spread
When discussing the significance of the team’s findings, Dr. Purcarea said their ability to resist modern antibiotics could represent a potential health risk, especially if they were allowed to share genetic material with modern bacteria.
“If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance,” the researcher explained.
Conversely, the researchers found several potential benefits in the ancient Psychrobacter strain. For example, they found 11 specific genes that may stop or even kill the growth of other bacteria, viruses, or fungi. Purcarea said this strain produces “unique enzymes and antimicrobial compounds” that could lead to the development of new antibiotics, industrial enzymes, and other biotechnological innovations.
“It can also inhibit the growth of several major antibiotic-resistant ‘superbugs’ and showed important enzymatic activities with important biotechnological potential,” Purcarea explained.
During the genetic analysis, the team found nearly 600 genes they described as having “unknown functions.” Given the organisms stron resistance profile, they said these uncharacterized genes could represent an “untapped source” for discovering novel biological mechanisms that could be exploited.
“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.”
The study “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” was published in Frontiers in Microbiology.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.