Scientists have discovered ancient bacteria, frozen for approximately 5,000 years in an underground ice cave in Romania, that exhibit resistance to ten different types of modern antibiotics. The finding, while potentially concerning in the context of rising antibiotic resistance globally, also offers a unique opportunity to understand the natural origins of these defenses and potentially discover new antimicrobial compounds.
The bacteria, named Psychrobacter SC65A.3, was isolated from a 25-meter (82-foot) ice core extracted from the Scărișoara Ice Cave. Researchers sequenced the bacterium’s genome and tested its susceptibility to 28 antibiotics, finding it was resistant to ten across eight classes, including ciprofloxacin, a broad-spectrum antibiotic commonly used to treat serious bacterial infections. , the findings are prompting further investigation into the evolutionary history of antibiotic resistance.
The discovery raises a seemingly paradoxical question: how could a bacterium frozen for millennia develop resistance to antibiotics that weren’t created until the 20th and 21st centuries? The answer, researchers explain, lies in the fact that antibiotic resistance isn’t a modern phenomenon. It’s a natural process that has been evolving in bacteria for billions of years as they compete with each other for resources.
“Studying microbes such as Psychrobacter SC65A.3 reveals how antibiotic resistance evolved naturally in the environment, long before modern antibiotics were ever used,” said Dr. Cristina Purcarea, a senior scientist at the Institute of Biology Bucharest of the Romanian Academy. This suggests that the mechanisms of resistance predate the widespread use – and overuse – of antibiotics in human medicine and agriculture.
Bacteria naturally produce a wide range of chemical compounds to defend themselves against other microbes. These compounds can kill or suppress competing bacteria, giving the producing organism a survival advantage. Over vast stretches of time, this “arms race” has resulted in a substantial reservoir of resistance genes and antimicrobial compounds. Many of our current antibiotics are, in fact, derived from these naturally occurring microbial compounds. Penicillin, for example, was originally discovered as a product of the Penicillium fungus.
The Scărișoara Ice Cave provides a unique environment for studying ancient bacteria. The ice core represents a timeline stretching back 13,000 years, offering a glimpse into microbial life from different eras. The extreme cold and high salt levels within the cave create a harsh environment where only resilient organisms can survive, potentially fostering the development and preservation of resistance mechanisms.
While the discovery of antibiotic resistance in ancient bacteria is not necessarily a direct threat to public health, it does highlight the potential for ancient microbes to contribute to the growing problem of antibiotic resistance. If climate change causes increased melting of ice caves and glaciers, these ancient microorganisms – and their resistance genes – could be released into the environment, potentially spreading to modern bacteria.
“If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance,” Dr. Purcarea explained. However, she also emphasized the potential benefits of studying these ancient organisms. The unique enzymes and antimicrobial compounds produced by Psychrobacter SC65A.3 could inspire the development of new antibiotics and other biotechnological innovations.
The research team drilled the 25-meter ice core from the Great Hall of the Scărișoara Ice Cave. Laboratory analysis revealed that the ancient bacteria thrived in harsh conditions, including extreme cold and high salt concentrations – environments that typically inhibit bacterial growth. This resilience further underscores the remarkable adaptability of these microorganisms.
The findings underscore the importance of understanding the natural history of antibiotic resistance. By studying ancient bacteria, scientists can gain valuable insights into the evolutionary processes that drive resistance and potentially identify novel strategies to combat the growing threat of superbugs. The research also serves as a reminder of the potential risks associated with climate change and the release of ancient microorganisms from melting ice.
Further research is needed to fully characterize the resistance mechanisms of Psychrobacter SC65A.3 and to assess the potential for horizontal gene transfer – the transfer of genetic material between bacteria – to modern strains. However, this discovery represents a significant step forward in our understanding of antibiotic resistance and its origins.
