In a breakthrough study from the University of Oregon, researchers have identified a molecule secreted by a common skin fungus that can effectively kill Staphylococcus aureus—a bacterium responsible for hundreds of thousands of hospitalizations annually in the United States. This skin fungi may hold the key to new antimicrobial therapies. The discovery points to a surprising new strategy in the global fight against antibiotic-resistant pathogens: leveraging the natural defenses found in the human skin microbiome.
The study, published in Current Biology, highlights how the yeast Malassezia, a predominant fungal inhabitant of human skin, metabolizes skin oils to produce fatty acids that exhibit strong antibacterial effects. Among these are hydroxy fatty acids capable of damaging and eliminating S. aureus, including strains resistant to existing drugs.
An overlooked player in the skin microbiome
While the gut microbiome has garnered significant scientific interest, the skin’s microbial community—particularly its fungal components—remains underexplored. Caitlin Kowalski, a postdoctoral researcher who led the study, emphasized this gap. “The skin is a parallel system to what’s happening in the gut, which is really well-studied,” Kowalski noted in a press release. “Skin is lipid-rich, and the skin microbiome processes these lipids to also produce bioactive compounds.”
Unlike bacteria, the fungal species Malassezia cannot synthesize fatty acids on their own and rely on the skin’s natural oils. This symbiotic relationship not only sustains the yeast but also results in the creation of bioactive molecules that can target harmful bacteria.
You can learn more about the human skin microbiome and its complexity through research by the National Institutes of Health.
Potent but selective: how fungi defend their niche
Kowalski’s team discovered that Malassezia sympodialis, a relatively harmless yeast found across human skin, converts skin lipids into hydroxy fatty acids with detergent-like properties. These acids were observed to rapidly compromise the bacterial cell membranes of S. aureus, causing their internal contents to leak and resulting in bacterial death within 15 minutes.
Crucially, the effect was highly dependent on the acidic environment typical of human skin. In laboratory conditions with neutral pH, the antimicrobial activity was absent. “I think that’s why in some cases we may have missed these kinds of antimicrobial mechanisms,” Kowalski said. “Because the pH in the lab wasn’t low enough. But human skin is really acidic.”
The specificity of these compounds opens up potential for targeted therapies that minimize disruption to beneficial microbes, a key limitation of broad-spectrum antibiotics.
Resistance still evolves—even with natural antimicrobials
Despite the promising results, the study also documented the eventual development of bacterial tolerance to the fungal fatty acids. Genomic analysis revealed mutations in the Rel gene of S. aureus, a key regulator of the bacterial stress response. Similar mutations have previously been identified in drug-resistant clinical strains, suggesting that even naturally derived compounds can select for resistance over time.
This finding complicates the push for using live microbes or their products as therapies. “There’s growing interest in applying microbes as a therapeutic,” Kowalski explained. “But it can have consequences that we have not yet fully understood.”
A new frontier in antibiotic discovery
Kowalski’s work underscores the potential of tapping into the skin’s native flora for next-generation antimicrobials. While Malassezia has traditionally been linked to conditions like dandruff or eczema, its role in modulating skin health and defending against pathogens is becoming clearer.
The research required three years of investigation and close collaboration with chemical microbiologists at McMaster University. Matthew Barber, an associate professor of biology at the University of Oregon and Kowalski’s adviser, likened the discovery process to molecular detective work: “It was like finding a needle in a haystack but with molecules you can’t see.”
This interdisciplinary effort also opens avenues for therapeutic development beyond antibiotics. If harnessed properly, lipid-processing microbes like Malassezia could lead to topical treatments that prevent or reduce colonization by antibiotic-resistant pathogens—particularly in hospital settings.
For further context on fungal research and drug development, refer to this review on fungal natural products from Current Opinion in Microbiology.
Future directions and ongoing research
Kowalski is currently expanding her work to explore the genetic mechanisms behind microbial resistance and is preparing to establish her own lab focused on the skin microbiome. Her team aims to uncover more microbial interactions that influence health and disease, potentially identifying new molecules with clinical applications.
Barber reflected on the broader implications: “Antibiotic-resistant bacterial infections are a major human health threat and one that, in some ways, is getting worse,” he said. “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.”
As antibiotic resistance continues to challenge modern medicine, this study offers a compelling reminder that novel solutions may be hiding in plain sight—on our very own skin.
Recommended For You
