Microbes that live in fishes’ slimy mucus coating could lead chemists to new antibiotic drugs

One day in the future, you may take a pill to treat an illness – and owe your recovery to the tiny microbes that flourish in the slippery layer of mucus that coats fishes.

It is critically important to find the next generation of antibiotics. The incidence of bacterial infections resistant to current antibiotics continues to climb. The World Health Organization has warned that this issue will only become more serious, and a recent study anticipates that by 2050 drug-resistant infections will affect more people than cancer.

Deaths attributed to antimicrobial resistance (AMR) globally is predicted to rise in the coming decades. Review on Antimicrobial Resistance, CC BY
But how do you find a new antibiotic?

Perhaps surprisingly, over 70 percent of currently used anti-infectives were derived from naturally occurring chemicals. Plants and microbes produce a diverse array of complex chemicals, some of which have antibiotic or antiviral properties, or even are toxic to cells. For example, amoxicillin is one of the most commonly prescribed antibiotics, and is a derivative of a chemical isolated from Penicillium mold.

Although many previous efforts to identify new anti-infectives have focused on soil microbes, microbes are all around us. In fact, they’re all over us and inside us. Animals, including humans, play host to a diverse community of microbes on the skin and within the gastrointestinal system.

There’s a growing consensus that these microbes can interact with their host organisms in both positive and negative ways, including supporting digestion and reducing pathogenic infections, but also contributing to some types of diseases. These microbes may also be a source for new antibiotics. For example, researchers recently identified a new antibiotic from a bacterium found in the human nose.

The mucus on the surface of fish can be slimy and is also a potential gold mine for bioactive compounds. FWC Fish and Wildlife Research Institute, CC BY-NC-ND
In my lab at Oregon State University, we’ve been working to identify the next generation of antibiotics from the microbes associated with animals. Our current efforts focus on the most diverse group of vertebrates, marine and freshwater fishes. Over 33,000 fish species have been identified, more than the sum of all other vertebrates on Earth. These animals often live in challenging environments, and are likely to support microbes that help them resist infections.

We collaborate with marine biologist Misty Paig-Tran at California State University Fullerton to obtain samples of mucus from a number of different Pacific fish species. Over several trawls, her team was able to collect coastal and some deep sea fishes, in total around 17 species. For instance, they brought back several pink surfperch from coastal waters, and from deeper waters, midwater eelpouts.