The discovery of an ancient bacterium, Psychrobacter SC65A.3dated 5000 years under the ice of Scărișoara cave in Romania it can be good and bad news at the same time. The article published on Frontiers Microbiology has shown that this bacterium is able to resist 10 antibiotics used in the modern world thanks to over 100 geniuses of resistance (the resistome). Not only that, the bacterium is able to block the growth of other microbes including viruses and fungi. Researchers from the Bucharest Institute of Biology of the Romanian Academy isolated the strain from samples taken from one of the most studied ice caves in the world, composed of 100,000 m3 of ice that take researchers back in time up to 13,000 years.
The microorganism isolated in these still little-studied habitats, which occupy 20% of the Earth’s surface, allow us to understand the evolutionary history of antimicrobial resistance. But 5000 years ago there were no antibiotics… how can they be resistant? Resistance is a natural phenomenon, which bacteria have been implementing since long before the clinical use of antibiotics, through various mechanisms that have evolved throughout history.
On the one hand, there are the possible applications bio-medical and industrial of new cold-resistant enzymes discovered. On the other, with the melting of ice Due to climate change, there is a risk that these ancient resistance genes could spread to other strains, creating new superbugs.
The findings of the study on the Psychrobacter SC65A.3 bacterium buried in the ice
Psychrobacter SC65A.3 is a bacterium isolated from a 25-meter ice core dating back to 5,000 years ago from the Scărișoara Cave, Romania. It grows best between 4 and 15 °C and is classified as polyextremophilei.e. capable of adapting to different extreme environmental conditions. In fact, the genus Psychrobacter, described in 1986, includes coccobacilli (an intermediate form between spheres and sticks) lovers of cold and salt that are rarely pathogenic for humans.
The most relevant data of the study is that, despite a thousand-year isolation (well before the modern era of antibiotics), this microorganism shows resistance to several current drugs. Out of 28 antibiotics tested, Psychrobacter SC65A.3 proved to be resistant to well 10including some commonly used to treat lung, skin, blood, and urinary system infections.
The secret lies in its genome: the DNA of this strain possesses over 100 genes linked to defense mechanisms. These include systems that expel drugs from the cell, enzymes capable of inactivating them, and structural modifications of cellular targets that render therapeutic molecules ineffective. In addition to this ability, the bacterium has key genes to compete in nature, inhibiting the growth of other microbes such as fungi, viruses and rival bacteria. This opens interesting prospects for research, suggesting the use of these molecules to develop new antimicrobials.
However, there is a flip side to the coin. A possible spread of these bacteria, favored by melting of icecould represent a danger to public health. If these ancient resistance genes spread among other modern microbes, they could enhance resistance to current drugs.
Antibiotic resistance is an ancient weapon of superbugs
Antibiotic resistance is not a modern invention of bacteria but a ancient natural phenomenonevolved over millions of years well before the advent of medicine. This is demonstrated precisely by Psychrobacter SC65A.3. This bacterium, which had remained frozen for 5,000 years, already possessed mechanisms in its DNA that prove useful in escaping the action of current drugs such as cephalosporins and fluoroquinolones.
How is this possible? The answer lies in the very origin of drugs. Many antibiotics, in fact, they mimic or derive from natural molecules that fungi or other microbes have always produced to fight each other (think of penicillin). It was then man, through chemistry, who introduced variations synthetic or semi-synthetic to enhance their effectiveness, but bacteria have evolved with biological shields to defend themselves from the original versions of these molecules.
In practice, what happened slowly in nature, the use of antibiotics on a large scale and without criteria has accelerated significantly. If the world’s population does not use antibiotics correctly, abusing them or taking them randomly, what can happen and is already happening now is that some strains of bacteria become resistant to these antibiotics. It is said that they “naturally develop resistance to antibiotics” and do not die. This can, for example, lead to a delay in finding an effective treatment.
Even some bacteria can become resistant to all existing antibiotics – superbugs – and consequently there is no effective therapy for bacterial infections. With these dynamics, some antibiotics could become literally useless and unfortunately they are estimated around 10 million deaths per year by 2050.
