BY THE OPTIMIST DAILY EDITORIAL TEAM

In the ongoing search for new antibiotics, researchers may have found an unlikely ally: the fungi quietly snacking on our skin oils. According to a new study led by scientists at the University of Oregon, a common yeast called Malassezia, known more for causing dandruff than curing disease, may have a hidden talent for fighting dangerous bacteria.

The research, published in Current Biology, identified a molecule secreted by Malassezia that can kill Staphylococcus aureus, a notorious pathogen that sends over half a million Americans to the hospital every year. Lead author Caitlin Kowalski, a postdoctoral researcher at the UO, says this could be a game-changer in tackling antibiotic resistance. “Fungi inhabiting human skin are an untapped resource for identifying new antibiotics,” she explained.

What Malassezia does (and why it matters)

Malassezia is no stranger to your skin. In fact, it dominates the skin microbiome in most people, especially in areas rich in oils and fats. While often associated with conditions like eczema or flaky scalps, this yeast is typically harmless. What makes it fascinating is its unique relationship with our skin’s lipids. Because it can’t produce its own fatty acids, Malassezia relies on the oils we naturally secrete to survive.

That dependency is also the secret to its antimicrobial power. When Malassezia feasts on skin oils, it churns out fatty acids that selectively target bacteria—specifically, Staphylococcus aureus. One in three people carry this bacteria in their nose without issue, but it can quickly become dangerous if it enters the body through a wound or abrasion.

“The hydroxy fatty acids we identified are detergent-like,” said Kowalski. “They essentially destroy the membranes of Staphylococcus aureus and cause its insides to leak out.” Lab tests showed the bacterial colonies were wiped out within 15 minutes.

The antimicrobial power of healthy skin

So why hasn’t this compound been noticed before? The answer, surprisingly, may be pH. Most lab studies are conducted in neutral environments, while healthy skin is naturally acidic. That acidity turns out to be the magic condition under which Malassezia‘s fatty acid becomes lethal to bacteria.

“In some cases, we may have missed these kinds of antimicrobial mechanisms because the pH in the lab wasn’t low enough,” Kowalski noted.

It took years to isolate and identify the compound, and the research required help from chemical microbiologists at McMaster University. “It was like finding a needle in a haystack but with molecules you can’t see,” said Kowalski’s advisor, Matthew Barber.

Not all fungi wear capes

Of course, there’s a catch. Staphylococcus aureus eventually developed tolerance to the fungal compound, evolving a mutation in its Rel gene, which triggers a bacterial stress response. In other words: no, this is not a one-fungus-fits-all fix.

“Even though we know antibiotics lead to the evolution of resistance, it hasn’t been considered when we think about applying microbes as a therapeutic,” Kowalski said. That means we have to be as cautious deploying helpful microbes as we are prescribing antibiotics.

The skin microbiome, long overshadowed by its more famous cousin in the gut, is finally getting its turn in the spotlight. Kowalski is now planning a new lab focused on exploring the complex and understudied world of skin-resident fungi. “The skin is a parallel system to what’s happening in the gut,” she said. “It’s lipid-rich, and the skin microbiome processes these lipids to also produce bioactive compounds.”

Big implications, tiny allies

The discovery underscores a growing appreciation for the invisible ecosystems living on and inside our bodies. It also opens the door to a new generation of antibiotics that may not come from synthetic labs, but from our own biology.

“Antibiotic-resistant bacterial infections are a major human health threat and one that, in some ways, is getting worse,” said Barber. “We still have a lot of work to do in understanding the microorganisms but also finding new ways that we can possibly treat or prevent those infections.”

Kowalski’s work suggests that the key to future medicines might just be quietly sitting on the surface of our skin.

Study source: Current Biology—Skin mycobiota-mediated antagonism against Staphylococcus aureus through a modified fatty acid