Frozen bacteria from 5,000 years ago show resistance to modern antibiotics

Bacteria have been hiding for thousands of years beneath the mountains of Romania, locked inside an underground ice cave that has quietly stored a frozen record of Earth’s past.

Layer by layer, year by year, ice built up and sealed away tiny life forms from another time. Some of those microbes have now come back into the light.

One strain stood out right away. It had been trapped in ice that formed 5,000 years ago, yet it can resist several antibiotics doctors depend on today.

At the same time, it can hold back some of the toughest drug-resistant bacteria found in hospitals. That strange mix of danger and potential is exactly why scientists can’t ignore it.

The bacteria that surprised researchers

This finding comes from a research team led by Dr. Cristina Purcarea, a senior scientist at the Institute of Biology Bucharest of the Romanian Academy.

“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 Dr. Purcarea.

“But it can also inhibit the growth of several major antibiotic-resistant ‘superbugs’ and showed important enzymatic activities with important biotechnological potential.”

Life in a deep freeze

Scarisoara Ice Cave is not a small freezer tucked into a hillside. It holds massive blocks of ancient ice.

The team drilled a 25-meter core from a part of the cave known as the Great Hall. That single column of ice preserved a frozen record stretching back 13,000 years.

To keep modern microbes out, the scientists handled the ice with care. They placed fragments in sterile bags and kept them frozen during transport.

Back in the lab, the researchers isolated different bacterial strains and sequenced their genomes. That let them see which genes help the bacteria survive in low temperatures and which ones are tied to antimicrobial resistance and activity.

Psychrobacter belongs to a group of bacteria adapted to cold environments. Some species can infect humans or animals.

Others are studied for their potential use in industry because cold-loving enzymes can work efficiently at low temperatures, which can save energy in manufacturing.

Resistance older than modern medicine

Antibiotic resistance often feels like a modern problem caused by overuse of drugs in hospitals and on farms. But this frozen strain tells a longer story.

“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,” said Dr. Purcarea.

The team tested SC65A.3 against 28 antibiotics from 10 classes that are routinely used to or reserved for treating bacterial infections. Some of these drugs are critical in clinical care. The strain resisted 10 of them.

“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,” noted Dr. Purcarea.

Among the antibiotics involved were rifampicin, vancomycin, and ciprofloxacin, which are used to treat diseases such as tuberculosis, colitis, and urinary tract infections.

SC65A.3 is also the first Psychrobacter strain shown to resist trimethoprim, clindamycin, and metronidazole. Those drugs are used for UTIs and infections of the lungs, skin, blood, and reproductive system.

The genome of SC65A.3 carries more than 100 resistance-related genes.

The finding suggests that even in isolation, long before hospitals and pharmacies existed, bacteria were already developing ways to defend themselves against natural antimicrobial compounds in their environment.

A double-edged sword

The findings raise a tough question. What happens if ancient microbes locked in ice are released as global temperatures rise?

“If melting ice releases these microbes, these genes could spread to modern bacteria, adding to the global challenge of antibiotic resistance,” said Dr. Purcarea.

“On the other hand, they produce unique enzymes and antimicrobial compounds that could inspire new antibiotics, industrial enzymes, and other biotechnological innovations.”

The promise and risk of ancient bacteria

When scientists mapped the genome of SC65A.3, they found almost 600 genes with functions no one fully understands yet. That is a huge stretch of genetic material still waiting to be figured out.

The experts also spotted 11 genes that could kill or slow the growth of other bacteria, fungi, and even viruses.

That kind of ability gets attention. The World Health Organization has warned for years that antibiotic resistance ranks among the biggest threats to global health.

Infections that doctors once cleared up with routine treatment are now harder to control and, in some cases, harder to survive. Some hospital “superbugs” shrug off multiple drugs.

“These ancient bacteria are essential for science and medicine, but careful handling and safety measures in the lab are essential to mitigate the risk of uncontrolled spread,” said Purcarea.

Frozen for thousands of years, this microbe has emerged into a world transformed by antibiotics.

Its survival shows that the struggle between bacteria and antimicrobial compounds did not begin in the 20th century, but has been playing out in nature for millennia.

The full study was published in the journal Frontiers in Microbiology.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–