(Auburn, AL) Imagine a child with eczema who scratches a patch of irritated skin. A tiny opening forms, invisible to the eye. Into that breach slips a common bacterium, Staphylococcus aureus. For many people, the bacteria would remain harmless. But in someone with a weakened skin barrier, the microbe can cling tightly, multiply, and trigger an infection that is difficult to control. In severe cases, staph spreads beyond the skin and becomes life-threatening. Resistant strains such as MRSA turn what should be a treatable infection into a medical nightmare, one that claims tens of thousands of lives each year in the United States alone.
The question that has puzzled researchers for years is why staph bacteria cling so tenaciously to human skin. A new study, co-led by Auburn University's Department of Physics alongside scientists in Belgium and the United Kingdom, has uncovered the answer. Published in Science Advances, the research shows that staph locks onto human skin with the strongest biological grip ever measured, stronger than superglue and nearly unmatched in nature.
At the center of this discovery is a bacterial protein called SdrD, which the pathogen uses like a grappling hook to attach itself to a human protein called desmoglein-1. The bond between the two is unlike anything seen before. It withstands forces so powerful that they rival the strength of some chemical bonds. This helps explain why staph bacteria remain attached to the skin even after scratching, washing, or sweating. "It is the strongest non-covalent protein-protein bond ever reported," says Rafael Bernardi, Associate Professor of Physics at Auburn University and one of the senior authors. "This is what makes staph so persistent, and it helps us understand why these infections are so difficult to get rid of."
The study also revealed that calcium, an element better known for strengthening bones, plays a key role in fortifying this bacterial grip. When calcium levels were reduced in laboratory experiments, the bond between SdrD and desmoglein-1 weakened significantly. When calcium was added back, the bond became even stronger. This finding is particularly relevant for patients with eczema, where calcium balance in the skin is disrupted. Instead of protecting the skin, these irregular levels may actually make staph's grip tighter. "We were surprised to see how much calcium contributed to the strength of this interaction," explains Priscila Gomes, a researcher in Auburn's Department of Physics and co-author of the study. "It not only stabilized the bacterial protein, it made the whole complex much more resistant to breaking."
To uncover these details, the team combined single-molecule experiments with advanced computational simulations. Using atomic force microscopy, researchers in Europe measured the force of a single staph bacterium attaching to human skin proteins. Meanwhile, Auburn physicists modeled the interaction atom by atom on powerful supercomputers. The two approaches converged on the same remarkable conclusion: SdrD's grip on desmoglein-1 is stronger than any other protein bond known in biology.
This discovery opens the door to new strategies for combating antibiotic-resistant infections. Instead of trying to kill bacteria directly, which often drives the evolution of resistance, scientists could design therapies that block or weaken bacterial adhesion. If staph cannot cling to the skin, the immune system has a better chance of clearing it before infection takes hold. "By targeting adhesion, we are looking at a completely different way to fight bacterial infections," Bernardi says. "We are not trying to destroy the bacteria, but to stop them from latching on in the first place."
For the Department of Physics at Auburn University, the study highlights the growing role of biophysics in addressing urgent problems in human health. By combining physical measurements, biological insights, and international teamwork, the researchers have solved a long-standing mystery of staph pathogenesis and uncovered a potential weakness that could be exploited in future therapies. As Gomes reflects, "This project shows how much can be achieved when different fields and different countries come together to answer questions that none of us could solve alone."
The discovery of the strongest protein bond in nature not only sets a new benchmark in biophysics but also provides a fresh perspective on how to outsmart one of the most stubborn pathogens in medicine.
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About Auburn's Computational Biophysics Group
The Computational Biophysics Group at Auburn University's Department of Physics uses advanced computer simulations to uncover how biological molecules behave under force. By blending physics, biology, and high-performance computing, the team develops cutting-edge software, collaborates with experimental partners worldwide, and trains the next generation of scientists at the interface of physics, chemistry, and life sciences.
