BATH, England — In the fight against antibiotic-resistant superbugs, scientists are leaving no stone unturned. Or in this case, no hot spring unexplored. Researchers from the University of Plymouth have turned their attention to the UK’s only geothermal spring, the iconic Roman Baths, in search of novel bacteria that could hold the key to developing new lifesaving antibiotics.
Antimicrobial resistance is one of the biggest threats to global health. In 2019 alone, an estimated 1.27 million people worldwide died from antibiotic-resistant infections, and this number is predicted to soar to 10 million per year by 2050 if new antibiotics aren’t found. Traditional sources of antibiotics, like soil bacteria, have been over-mined, leading to a frustrating rediscovery of known compounds. This has spurred researchers to explore uncharted territories for antibiotic-producing microbes, including thermal hot springs.
The Roman Baths, steeped in history and famed since ancient times for their purported medicinal properties, present an intriguing prospect. Fed by the King’s Spring at a toasty 42°C (107.6°F), the waters flow into the Great Bath where they cool to around 30°C (86°F). These warm, mineral-rich waters support complex communities of bacteria and archaea (single-celled organisms distinct from bacteria), many of which are found nowhere else on Earth.
“People have visited the springs in Bath for thousands of years, worshipping at, bathing in and drinking the waters over the centuries. Even in the Victorian period the Spa Treatment Centre in Bath used the natural spring waters for their perceived curative properties in all sorts of showers, baths and treatments,” explained study co-author Zofia Matyjaszkiewicz, Collections Manager at the Roman Baths, in a statement. “It’s really exciting to see cutting-edge scientific research like this taking place here, on a site with so many stories to tell.”
To map out this microbial treasure trove, the researchers collected samples of water, sludge-like biofilm, and sediment from the King’s Spring and Great Bath. Back in the lab, they extracted and sequenced DNA from these samples to identify the types of microbes present, and also attempted to grow pure cultures of interesting bacteria.
The unprecedented DNA analysis, published in the journal The Microbe, revealed stark differences between the King’s Spring and the cooler Great Bath. The hotter King’s Spring was dominated by heat-loving archaea, whereas the Great Bath favored more commonplace bacteria. The biofilms and sediments from both sites harbored an astonishing diversity of bacteria, some of them representing completely new groups of organisms.
Of particular interest were members of the Actinobacteria and Myxococcota phyla, known to be prolific producers of antibiotic compounds. Although not abundant overall, several noteworthy genera from these groups were detected, hinting at untapped antibiotic potential.
Excitingly, when the researchers tested their bacterial isolates against dangerous pathogens, including the notorious ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species), 15 strains showed potent, broad-spectrum antibiotic activity. Surprisingly, these were not the usual suspects from the Actinobacteria, but rather less-explored groups like Pseudomonas and Enterococcus.
One standout was a strain related to Clostridium swellfunianum, which strongly inhibited several difficult-to-treat Gram-negative pathogens when grown at its preferred toasty temperature of 45°C (113°F). This finding underscores the importance of studying bacteria in conditions that mimic their natural environments to coax out their full antibiotic-producing potential.
The researchers plan to further mine this microbial goldmine by fully sequencing the genomes of their most promising isolates, as well as the collective genomes (metagenomes) of the entire microbial community. This will allow them to identify the specific genes and pathways responsible for antibiotic production, paving the way for the discovery of truly novel compounds.
“This is a really important, and very exciting, piece of research. Antimicrobial resistance is recognized as one of the most significant threats to global health, and the hunt for novel antimicrobial natural products is gathering pace. This study has for the first time demonstrated some of the microorganisms present within the Roman Baths, revealing it as a potential source of novel antimicrobial discovery,” said senior author Dr Lee Hutt, Lecturer in Biomedical Sciences at the University of Plymouth, in a statement. “There is no small irony in the fact the waters of the Roman Baths have long been regarded for their medicinal properties and now, thanks to advances in modern science, we might be on the verge of discovering the Romans and others since were right.”
The Roman Baths study provides compelling evidence that thermal hot springs are a fertile ground for antibiotic discovery. As we continue to lose the arms race against drug-resistant superbugs, these ancient waters could hold the key to developing the antibiotics of the future. The cure for the next pandemic might just be lurking in nature’s hot tubs, waiting to be discovered.