Scientists Discover ‘Kill Switch’ in Superbugs, Paving Way for Recent Antibiotics
Drug-resistant bacteria pose an escalating global health threat, but a recent breakthrough from Caltech researchers offers a glimmer of hope. Scientists have identified a critical vulnerability in bacteria – a protein called MurJ – that viruses exploit to disable and destroy these superbugs. This discovery, published in Nature on February 26, 2026, could revolutionize the development of a new class of antibiotics.
The Growing Crisis of Antibiotic Resistance
The rise of antibiotic-resistant bacteria is a pressing public health concern. As Bil Clemons, the Arthur and Marian Hanisch Memorial Professor of Biochemistry at Caltech, explains, “Evolution is powerful, and in bacteria, resistance to antibiotics develops quickly. This means that we now deal with bacteria that are resistant to all the medicines that we have.” The Centers for Disease Control and Prevention (CDC) estimates that tens of thousands of people die each year in the U.S. Alone from infections caused by antibiotic-resistant bacteria, and that number is rapidly increasing.
Targeting the Bacterial Cell Wall
Researchers have long focused on the peptidoglycan biosynthesis pathway – the process bacteria leverage to build their cell walls – as a potential target for new antibiotics. Peptidoglycan is unique to bacteria, making it an attractive target because it doesn’t harm human cells. Existing antibiotics like penicillin, discovered by Alexander Fleming, disrupt this pathway, but bacteria have evolved resistance to many of these drugs.
MurJ: A Key Protein in Cell Wall Construction
The research team honed in on MurJ, a small transporter protein vital for moving building blocks across the bacterial inner membrane during peptidoglycan synthesis. Three essential proteins – MraY, MurG, and MurJ – perform together to transport these components. Blocking any of these proteins can halt cell wall production and kill the bacterium.
How Viruses Disable MurJ
The breakthrough came from studying bacteriophages, viruses that infect bacteria. To replicate, phages must break through the bacterial cell wall. Researchers discovered that several unrelated phages disable MurJ using specialized proteins called single-gene lysis proteins (Sgls). Yancheng Evelyn Li, a graduate student in Clemons’ lab and lead author of the study, used cryo-electron microscopy to determine how these viral proteins work.
Li found that SglM, SglPP7, and SglCJ3 all bind to MurJ, locking it in an outward-facing position and preventing it from transporting the necessary building blocks for cell wall construction. “both of these Sgls bind to MurJ in an outward-facing conformation, locking it into this position,” Li says. The outward-facing form of MurJ is accessible to potential drugs, making it a promising target.
Convergent Evolution: A Strong Signal
What surprised researchers was that these different viral proteins, with no evolutionary connection, all target MurJ in the same way. This “convergent evolution” strongly suggests that MurJ is a critical vulnerability in bacteria. Clemons notes, “This is a third genome that evolved a distinct peptide to inhibit the same target in a similar way. It is the first strong evidence that evolution identifies MurJ as a great target for killing bacteria, which means we should follow evolution’s lead and develop therapeutics that target MurJ.”
Future Directions
The Caltech team plans to continue studying phages to identify more Sgls and gain further insights into how they target MurJ. This research could pave the way for the development of new antibiotics that exploit this bacterial weakness, offering a much-needed weapon in the fight against antibiotic resistance. “Our path is set on leveraging Sgl discovery, and we hope to continue to be supported to turn these concepts into realities,” Clemons says.