It has been 30 years since the last new class of antibiotic was introduced to the market. All the existing drugs are essentially variations on a theme: they kill bacteria, in similar ways. Some burst cells walls, others block DNA replication.

But the bacteria are swiftly evolving to survive those chemical attacks – and as they survive, they become virulent superbugs. Without new antibiotics, by 2050 the death toll from drug-resistant infections is projected to reach 10 million people a year, making the coronavirus pandemic seem almost quaint.

This is why scientists at Plymouth University have been searching the cold, dark abyss of the north Atlantic – where they have found sponges that contain powerful molecules capable of killing those superbugs.

Kerry Howell, professor of deep-sea ecology, and her colleagues have been carefully collecting specimens of these plant-like animals, bringing them back to the lab and testing pulverised extracts against stubborn, disease-causing bacteria. Among the deep-sea molecules, they are finding promising bactericidal novelties.

“We don’t actually know exactly what they are yet,” says Prof Mat Upton, a microbiologist who leads the laboratory side of the biodiscovery programme at Plymouth. “We’ve got compounds that kill bacteria that we want to try to kill, and we have a pretty good idea that they are new compounds. It is early, but things are progressing through the pipeline.”

The hit rate for finding powerful and useful new compounds is proving to be especially high among animals of the deep sea. Hundreds of biologically active compounds have been found at the bottom of the ocean, some already in widespread use. Enzymes found in bacteria living around hydrothermal vents are even being used in tests for the Covid virus.

Yet novel antibiotics and an untold variety of beneficial molecules could easily be wiped out if ecosystems around vents and elsewhere on the ocean floor were to be destroyed by deep-sea mining, which could go ahead in less than two years. Even after 40 years of scientific research since hydrothermal vents were first found, a tremendous amount is still being discovered about these extreme ecosystems, which thrive in scorching, toxic waters pouring through cracks in the deep seabed, miles underwater.

Howell says: “Part of the big concern that all deep-sea ecologists have is that we know just how little is known about these areas and we are desperately trying to play catch-up with the [deep-sea mining] industry. To my mind, that’s the wrong way round. We ought to be finding out about these places before we even consider mining them.”

One of the potential targets for deep-sea mining is the south-east Atlantic abyss, where Howell is planning her next expedition, along with South African colleagues. “It’s one of the least-explored parts of our planet. There’s really very little data,” she says .