Fungi dwelling on human skin may provide new antibiotics

A yeast known as Malassezia protects skin against bacterial infections — up to a certain point

University of Oregon

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University of Oregon researchers have uncovered a molecule produced by yeast living on human skin that showed potent antimicrobial properties against a pathogen responsible for a half-million hospitalizations annually in the United States. 

It’s a unique approach to tackling the growing problem of antibiotic-resistant bacteria. With the global threat of drug-resistant infections, fungi inhabiting human skin are an untapped resource for identifying new antibiotics, said Caitlin Kowalski, a postdoctoral researcher at the UO who led the study. 

Described in a paper published April 14 in Current Biology, the common skin fungus Malassezia gobbles up oil and fats on human skin to produce fatty acids that selectively eliminate Staphylococcus aureus. One out of every three people have Staphylococcus aureus harmlessly dwelling in their nose, but the bacteria are a risk factor for serious infections when given the opportunity: open wounds, abrasions and cuts. They’re the primary cause of skin and soft tissue infections known as staph infections. 

Staphylococcus aureus is also a hospital superbug notorious for being resistant to current antibiotics, elevating the pressing need for new medicines. 

There are lots of studies that identify new antibiotic structures, Kowalski said, “but what was fun and interesting about ours is that we identified (a compound) that is well-known and that people have studied before.” 

The compound is not toxic in normal lab conditions, but it can be potent in conditions that replicate the acidic environment of healthy skin. 

“I think that’s why in some cases we may have missed these kinds of antimicrobial mechanisms,” Kowalski added, “because the pH in the lab wasn’t low enough. But human skin is really acidic.” 

Humans play host to a colossal array of microorganisms, known as the microbiome, but we know little about our resident fungi and their contributions to human health, Kowalski said. The skin microbiome is of special interest to her because while other body parts crowd dozens of different fungi, the skin is dominantly colonized by one kind known as Malassezia. 

Malassezia can be associated with cases of dandruff and eczema, but it’s considered relatively harmless and a normal part of skin flora. The yeast has evolved to live on mammalian skin, so much so that it can’t make fatty acids without the lipids — oils and fats — secreted by skin. 

Despite the abundance of Malassezia found on us, they remain understudied, Kowalski said. 

“The skin is a parallel system to what’s happening in the gut, which is really well-studied,” she said. “We know that the intestinal microbiome can modify host compounds and make their own unique compounds that have new functions. Skin is lipid-rich, and the skin microbiome processes these lipids to also produce bioactive compounds. So what does this mean for skin health and diseases?” 

Looking at human skin samples from healthy donors and experiments done with skin cells in the lab, Kowalski found that the fungal species Malassezia sympodialis transformed host lipids into antibacterial hydroxy fatty acids. Fatty acids have various functions in cells but are notably the building blocks for cell membranes. 

The hydroxy fatty acids synthesized by Malassezia sympodialis were detergent-like, destroying the membranes of Staphylococcus aureus and causing its internal contents to leak away. The attack prevented the colonization of Staphylococcus aureus on the skin and ultimately killed the bacteria in as little as 15 minutes, Kowalski said. 

But the fungus isn’t a magic bullet. After enough exposure, the staph bacteria eventually became tolerant to the fungus, as they do when clinical antibiotics are overused. 

Looking at their genetics, the researchers found that the bacteria evolved a mutation in the Rel gene, which activates the bacterial stress response. Similar mutations have been previously identified in patients with Staphylococcus aureus infections. 

The findings show that a bacteria’s host environment and interactions with other microbes can influence its susceptibility to antibiotics. 

“There’s growing interest in applying microbes as a therapeutic, such as adding bacteria to prevent the growth of a pathogen,” Kowalski said. “But it can have consequences that we have not yet fully understood. Even though we know antibiotics lead to the evolution of resistance, it hasn’t been considered when we think about the application of microbes as a therapeutic.” 

While the discovery adds a layer of complexity for drug discovery, Kowalski said she is excited about the potential of resident fungi as a new source for future antibiotics. 

Identifying the antimicrobial fatty acids took three years and a cross-disciplinary effort. Kowalski collaborated with chemical microbiologists at McMaster University to track down the compound. 

“It was like finding a needle in a haystack but with molecules you can’t see,” said Kowalski’s adviser, Matthew Barber, an associate professor of biology in the College of Arts and Sciences at the UO. 

Kowalski is working on a follow-up study that goes deeper into the genetic mechanisms that led to the antibiotic tolerance. She is also preparing to launch her own lab to further investigate the overlooked role of the skin microbiome, parting from Barber’s lab after bringing fungi into focus. 

“Antibiotic-resistant bacterial infections are a major human health threat and one that, in some ways, is getting worse,” Barber 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.” 

— By Leila Okahata, University Communications

This work was supported by the National Science Foundation, National Institutes of Health, L’Oreal USA for Women in Science Fellowship and Helen Hay Whitney Foundation Fellowship. 

About the University of Oregon College of Arts and Sciences 
The University of Oregon College of Arts and Sciences supports the UO’s mission and shapes its identity as a comprehensive research university. With disciplines in humanities and social and natural sciences, the College of Arts and Sciences serves approximately two-thirds of all UO students. The College of Arts and Sciences faculty includes some of the world’s most accomplished researchers, and the more than $75 million in sponsored research activity of the faculty underpins the UO’s status as a Carnegie Research I institution and its membership in the Association of American Universities.

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Journal

Current Biology

DOI

10.1016/j.cub.2025.03.055 

Article Title

Skin mycobiota-mediated antagonism against Staphylococcus aureus through a modified fatty acid

Article Publication Date

14-Apr-2025

 

Dopamine signals when a fear can be forgotten

Study shows how a dopamine circuit between two brain regions enables mice to extinguish fear after a peril has passed

Picower Institute at MIT

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image: 

An edited version of a figure from the research shows the ventral tegmental area, highlighting dopamine-associated neurons in green and one that connects to the posterior amygdala (magnified in inset) in red

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Credit: Tonegawa Lab/MIT Picower Institute

Dangers come but dangers also go and when they do, the brain has an “all-clear” signal that teaches it to extinguish its fear. A new study in mice by MIT neuroscientists shows that the signal is the release of dopamine along a specific interregional brain circuit. The research therefore pinpoints a potentially critical mechanism of mental health, restoring calm when it works, but prolonging anxiety or even post-traumatic stress disorder when it doesn’t.

“Dopamine is essential to initiate fear extinction,” said Michele Pignatelli di Spinazzola, co-author of the new study from the lab of senior author Susumu Tonegawa, Picower Professor of biology and neuroscience at the RIKEN-MIT Laboratory for Neural Circuit Genetics in The Picower Institute for Learning and Memory and an HHMI Investigator.

In 2020 Tonegawa’s lab showed that learning to be afraid, and then learning when that’s no longer necessary, result from a competition between populations of cells in the brain’s amygdala region. When a mouse learns that a place is “dangerous” (because it gets a little foot shock there), the fear memory is encoded by neurons in the anterior of the basolateral amygdala (aBLA) that express the gene Rspo2. When the mouse then learns that a place is no longer associated with danger (because they wait there and the zap doesn’t recur), neurons in the posterior basolateral amygdala (pBLA) that express the gene Ppp1r1b encode a new fear extinction memory that overcomes the original dread. Notably those same neurons encode feelings of reward, helping to explain why it feels so good when we realize that an expected danger has dwindled.

In the new study, the lab, led by former members Xiangyu Zhang and Katelyn Flick, sought to determine what prompts these amygdala neurons to encode these memories. The rigorous set of experiments the team reports in the Proceedings of the National Academy of Sciences show that it’s dopamine sent to the different amygdala populations from distinct groups of neurons in the ventral tegmental area (VTA).

“Our study uncovers a precise mechanism by which dopamine helps the brain unlearn fear,” said Zhang, who also led the 2020 study and is now Senior Associate at Orbimed, a healthcare investment firm. “We found that dopamine activates specific amygdala neurons tied to reward, which in turn drive fear extinction. We now see that unlearning fear isn’t just about suppressing it—it’s a positive learning process powered by the brain’s reward machinery. This opens up new avenues for understanding and potentially treating fear-related disorders like PTSD.”

Forgetting fear

The VTA was the lab’s prime suspect to be the source of the signal because the region is well known for encoding surprising experiences and instructing the brain, with dopamine, to learn from them. The first set of experiments in the paper used multiple methods for tracing neural circuits to see whether and how cells in the VTA and the amygdala connect. They found a clear pattern: Rspo2 neurons were targeted by dopaminergic neurons in the anterior and left and right sides of the VTA. Ppp1r1b neurons received dopaminergic input from neurons in the center and posterior sections of the VTA. The density of connections was greater on the Ppp1r1b neurons than for the Rspo2 ones.

The circuit tracing showed that dopamine is available to amygdala neurons that encode fear and its extinction, but do those neurons care about dopamine? The team showed that indeed they express “D1” receptors for the neuromodulator. Commensurate with the degree of dopamine connectivity, Ppp1r1b cells had more receptors than Rspo2 neurons.

Dopamine does a lot of things, so the next question was whether its activity in the amygdala actually correlated with fear encoding and extinction. Using a method to track and visualize it in the brain, the team watched dopamine in the amygdala as mice underwent a three-day experiment. On day one they went to an enclosure where they experienced three little zaps on the feet. On day two they went back to the enclosure for 45 minutes where they didn’t experience any new shocks –at first the mice froze in fear but then relaxed after about 15 minutes. On day 3 they returned again to test whether they had indeed extinguished the fear they showed at the beginning of day 2.

The dopamine activity tracking revealed that during the shocks on day 1, Rspo2 neurons had the larger response to dopamine, but in the early moments of day 2 when the anticipated shocks didn’t come and the mice eased up on freezing in fear, the Ppp1r1b neurons showed the stronger dopamine activity. More strikingly, the mice that learned to extinguish their fear most strongly also showed the greatest dopamine signal at those neurons.

Causal connections

The final sets of experiments sought to show that dopamine is not just available and associated with fear encoding and extinction, but also actually causes them. In one set, they turned to optogenetics, a technology that enables scientists to activate or quiet neurons with different colors of light. Sure enough, when they quieted VTA dopaminergic inputs in the pBLA, doing so impaired fear extinction. When they activated those inputs, it accelerated fear extinction. The researchers were surprised that when they activated VTA dopaminergic inputs into the aBLA they could reinstate fear even without any new foot shocks, impairing fear extinction.

The other way they confirmed a causal role for dopamine in fear encoding and extinction was to manipulate the amygdala neurons’ dopamine receptors. In Ppp1r1b neurons, overexpressing dopamine receptors impaired fear recall and promoted extinction, whereas knocking the receptors down impaired fear extinction. Meanwhile in the Rspo2 cells, knocking down receptors reduced the freezing behavior.

“We showed that fear extinction requires VTA dopaminergic activity in the pBLA Ppp1r1b neurons by using optogenetic inhibition of VTA terminals and cell-type-specific knockdown of D1 receptors in these neurons,” the authors wrote.

The scientists are careful in the study to note that while they’ve identified the “teaching signal” for fear extinction learning, the broader phenomenon of fear extinction occurs brainwide, rather than in just this single circuit.

But the circuit seems to be a key node to consider as drug developers and psychiatrists work to combat anxiety and PTSD, Pignatelli di Spinazzola said.

“Fear learning and fear extinction provide a strong framework to study generalized anxiety and PTSD,” he said. “Our study investigates the underlying mechanisms suggesting multiple targets for a translational approach such as pBLA and use of dopaminergic modulation.”

Marianna Rizzo is also a co-author of the study. Support for the research came from the RIKEN Center for Brain Science, the Howard Hughes Medical Institute, the Freedom Together Foundation and The Picower Institute for Learning and Memory.

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Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2501331122 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Dopamine induces fear extinction by activating the reward-responding amygdala neurons

Article Publication Date

28-Apr-2025

 

Anatomy of a “zombie” volcano: investigating the cause of unrest inside Uturuncu

University of Oxford

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image: 

Gravimeter and GPS station with Cerro Uturuncu in the background. Photo credit Duncan Muir, Cardiff University.

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Credit: Duncan Muir, Cardiff University.

Images available via the link in the notes section

Scientists from China, the UK and the USA have collaborated to analyse the inner workings of Bolivia’s “zombie” volcano, Uturuncu. By combining seismology, physics models and analysis of rock composition, researchers identify the causes of Uturuncu’s unrest, alleviating fears of an imminent eruption. The findings have been published today (28 April) in the journal PNAS.

Deep in the Central Andes lies Uturuncu, Bolivia’s “zombie” volcano -so called because despite being technically dead (last erupting 250 thousand years ago), it still shows signs of unrest, including earthquakes and plumes of gases. This unrest manifests itself in a “sombrero” pattern of deformation, with the land in the centre of the volcanic system rising up, and surrounding areas sinking down.

For the local population, it is vitally important to assess the potential start and severity of an eruption from Uturuncu, which could cause widespread damage and threat to life. However, up to now there was no explanation for the continued volcanic unrest. Scientists believed that the key to understanding this was to visualise the way that magma and gases move around underneath the volcano.

This new study, which drew upon expertise from University of Science and Technology of China, the University of Oxford and Cornell University, used signals detected from more than 1,700 earthquake events to perform high-resolution imaging of the plumbing system in the shallow crust beneath Uturuncu. According to the findings, the “zombie”-like unrest of Uturuncu is due to the movement of liquid and gas beneath the crater, with a low likelihood of an imminent eruption.

Volcanic plumbing systems are a complex mixture of fluids and gases in magmatic reservoirs and hydrothermal systems. Previous studies have shown that Uturuncu sits above the world’s largest known magma body in the Earth’s crust, the Altiplano-Puna Volcanic Complex, and that an active hydrothermal system connects this body and the surface. But it was unknown how fluids may be moving through this underground system.

The research team made use of seismic tomography, a way of imaging the interior of the volcano, similar to methods used in medical imaging of the human body.  Seismic waves travel at different speeds through different materials, thereby providing high-resolution insights into the inner workings of Uturuncu in three dimensions. They combined this with analysis of the physical properties of the system, including rock composition, to better understand the subterranean volcanic system. This detailed analysis picked out possible upward migration pathways of geothermally heated fluids and showed how liquids and gases accumulate in reservoirs directly below the volcano’s crater. The research team believe that this is the most likely cause for the deformation in the centre of the volcanic system, and that the risk of a real eruption is low.

Co-author Professor Mike Kendall (Department of Earth Sciences, University of Oxford) said: “I am very pleased to be involved in this truly international collaboration. Our results show how linked geophysical and geological methods can be used to better understand volcanoes, and the hazards and potential resources they present.”

Co-author Professor Haijiang Zhang (School of Earth and Space Sciences, University of Science and Technology of China) said: “Understanding the anatomy of the Uturuncu volcanic system was only possible thanks to the expertise within the research team. This enabled us to combine various advanced geophysical imaging tools with modelling of the rock properties and their interactions with fluids.”

Co-author Professor Matthew Pritchard (Cornell University) added: "The methods in this paper could be applied to the more than 1400 potentially active volcanoes and to the dozens of volcanoes like Uturuncu that aren't considered active but that show signs of life — other potential zombie volcanoes." 

The research team hope that similar studies using the joint analysis of seismological and petrological properties can be used to view the anatomy of other volcanic systems in the future.

Notes to editors:

For media enquiries and interview requests, contact communications@earth.ox.ac.uk

The paper ‘Anatomy of magmatic hydrothermal system beneath Uturuncu volcano, Bolivia, by joint seismological and petrophysical analysis’ will be published in PNAS at 20:00 BST / 15:00 ET Monday 28 April, DOI 10.1073/pnas.2420996122

A pre-embargo copy of the paper can be viewed on the PNAS tipsheet on EurekAlert.

Images relating to the study which can be used in articles can be found at https://drive.google.com/drive/folders/1TXieDDIKOsfEp8imld9qpZRCtrYJ-p85?usp=sharing  These images are for editorial purposes relating to this press release ONLY and MUST be credited (see file name). They MUST NOT be sold on to third parties.

Cerro Uturuncu, one of many volcanoes on the Bolivian Altiplano that lie above the Altiplano-Puna Magma Body. Photo credit Jon Blundy, University of Oxford.

Cerro Uturuncu, right, and Cerro San Antonio, left, volcanoes above the small town of Quetena Chico on the Bolivian Altiplano. Photo Credit: Jon Blundy, University of Oxford.

About the University of Oxford

Oxford University has been placed number 1 in the Times Higher Education World University Rankings for the ninth year running, and ​number 3 in the QS World Rankings 2024. At the heart of this success are the twin-pillars of our ground-breaking research and innovation and our distinctive educational offer.

Oxford is world-famous for research and teaching excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research alongside our personalised approach to teaching sparks imaginative and inventive insights and solutions.

Through its research commercialisation arm, Oxford University Innovation, Oxford is the highest university patent filer in the UK and is ranked first in the UK for university spinouts, having created more than 300 new companies since 1988. Over a third of these companies have been created in the past five years. The university is a catalyst for prosperity in Oxfordshire and the United Kingdom, contributing £15.7 billion to the UK economy in 2018/19, and supports more than 28,000 full time jobs.

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Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2420996122 

Article Title

Anatomy of the magmatic hydrothermal system beneath Uturuncu volcano, Bolivia, by joint seismological and petrophysical analysis

Article Publication Date

28-Apr-2025

 

Some dogs, cats bred to evolve same ‘smushed’ faces

Cornell University

For the first time, scientists at Cornell University and Washington University have uncovered examples of how selection pressures from breeding cats and dogs have led to “convergence” – the tendency of unrelated animals and plants to evolve similar characteristics under similar environmental conditions.

In this case, the researchers found remarkable examples of convergence both within these two domesticated species and also between them. The convergence showed up in breeds with short faces, technically referred to as brachycephalic or “smushed” faces.

As a result of artificial selection from breeding, certain breeds of these two species – which shared a common ancestor but have been evolutionarily separated for 50 million years – have converged to such an extreme that they are more similar to each other than they are to most members of their own species or their ancestors. This phenomenon hadn’t previously been observed in domesticated species, according to the paper, which is under embargo until 3pm ET on Monday, April 28 in PNAS.

When the researchers measured the skulls of brachycephalic dogs and cats, they found strikingly similar overlap between these breeds from two different species.

“Persian cats and pug and Pekingese dogs all have skull shapes that are very similar to each other, with flat and short faces, and their muzzles and palettes are tilted up in the same way,” said Abby Drake, senior lecturer at Cornell. Drake is a corresponding author on the paper along with Jonathan Losos, professor of biology at Washington University.

The same pattern of convergence has occurred multiple times within each species. In dogs, it occurred in bulldog breeds, but then separately in Asian dog breeds such as Pekingese and Shih Tzu. In cats, the same traits can be seen in Persian, Himalayan and Burmese breeds.

When convergence occurs through natural selection – such as in the development of wings in birds, bats and insects – it is usually a sign of a successful trait. In the case of domesticated species, evolution happens so rapidly, it can offer insight into evolutionary processes, Drake said.

The researchers mapped the skull shapes, compared them and discovered these similarities, even though the ancestors of cats and dogs looked quite different. Dogs descended from wolves, a larger animal with a long muzzle, while cats descended from wildcats, which are smaller animals with a shorter face and a snout.

“They start off in different places,” Drake said, “but because humans applied the same selection pressures, they evolved to look almost identical to each other.”

Artificial selection from breeding has led to a remarkable diversity of both cats and dogs, though dog diversity is even more extreme. It turns out dogs as a species are more diverse than the entire order of Carnivora.

“We’re seeing this very large evolutionary variation within a species that’s only been evolving for a relatively very short amount of time,” Drake said. “That’s a remarkable thing to see in evolution, which takes millions of years, but we did it with dogs by pushing them to the extremes.”

In this study, the team similarly found that cats are more diverse as a species than the entire family of Felidae, which has 41 species.

Unfortunately, Drake said, humans have pushed brachycephalic breeds to such extremes that they’re susceptible to breathing, eating and birthing issues and wouldn’t survive in the wild.

In the study, the researchers collected three-dimensional measurements of skull morphology from CT scans of domestic cats, dogs, wildcats, wolves, species within the Canidae (dog) family and from the Felidae (cat) family, and additional species such as weasels and walruses from the order Carnivora. These were acquired from veterinary institutions, museum collections and MorphoSource, a natural history digital archive.

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Journal

Proceedings of the National Academy of Sciences

Article Title

Copy-Cat Evolution: Divergence and Convergence Within and Between Cat and Dog Breeds

Article Publication Date

28-Apr-2025

 

Sexism undermines teams by disrupting emotional synchrony’s role in performance

Groundbreaking research highlights the hidden cost of sexual harassment on collaboration and innovation

Bar-Ilan University

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In a world where innovation and progress depend on effective teamwork, a new study reveals how sexist behavior within teams sabotages not just individuals, but the very fabric of collaboration.

Researchers found that exposure to sexist comments significantly alters how women interact emotionally during teamwork, increasing a key ingredient of successful collaboration: emotional synchrony. Emotional synchrony—shared, temporally aligned facial expressions among team members—has long been known to enhance trust, coordination, and performance. But this study, published in the Proceedings of the National Academy of Sciences, shows that under threat of sexism, synchrony is repurposed from driving performance to simply fostering social bonding potentially as a defense mechanism.

“Sexism doesn’t just harm individuals—it actively rewires how teams function,” said one of the study’s authors, Prof. Ilanit Gordon, from the Department of Psychology and Gonda (Goldschmied) Multidisciplinary Brain Research Center at Bar-Ilan University and the Child Study Center at the Yale University School of Medicine. “We saw that emotional alignment, which usually helps people work better together, loses its impact for performance when women are subjected to sexist remarks.” Gordon collaborated on the study with Bar-Ilan University PhD student Alon Burns, Prof. Sharon Toker from Tel Aviv University and Prof. Yair Berson from McMaster University.

The research involved 177 all-women dyads collaborating on a task via video conferencing. Participants were randomly assigned to a control group or a sexism condition, in which they received subtle sexist comments from an actor posing as an experimenter leading the study. Advanced facial recognition software tracked the emotional expressions of each participant throughout the task.

The results were striking: While emotional synchrony predicted improved team performance in the control condition, it had no such benefit when teams were exposed to sexism. In fact, synchrony increased in the sexism condition—signaling greater social bonding—but this did not translate into better outcomes.

“Our findings suggest that emotional synchrony under sexism threat is heightened yet redirected toward social coping, rather than collaborating,” Gordon noted. “This shift might weaken the ability or willingness of teams to stay focused on shared goals.”

The implications are clear: creating environments where women feel safe is not only a moral imperative, but also a strategic one. The researchers emphasize that zero-tolerance policies for sexual harassment are essential for maintaining the integrity and effectiveness of team-based work.

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Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2409708122 

Article Title

Sexism in Teams: Exposure to sexist comments increases emotional 5 synchrony but eliminates its benefits for team performance