Evolution has identified MurJ as a great target for killing bacteria
In the long war between human medicine and bacterial adaptation, nature itself may have already mapped the path forward. Researchers at Caltech have found that three unrelated bacteriophages — viruses that prey on bacteria — independently evolved proteins that disable MurJ, a protein essential to building the bacterial cell wall. This convergence, reported in Nature in February 2026, suggests that evolution has quietly identified a vulnerability that medicine has yet to fully exploit, offering a potential new direction in the fight against antibiotic-resistant infections that claim tens of thousands of American lives each year.
- Antibiotic-resistant bacteria are killing tens of thousands of Americans annually, and the medical community's existing arsenal is increasingly powerless against evolving strains.
- The critical gap is not just resistance to current drugs, but a failure to identify and target new biological weak points in bacterial survival — a problem that has persisted for decades.
- Caltech researchers discovered that three entirely unrelated viruses each independently evolved proteins that freeze MurJ, a bacterial protein essential for cell wall construction, effectively killing the bacterium.
- The striking convergence — three separate evolutionary paths arriving at the same molecular solution — signals to scientists that MurJ is not merely a target, but likely the target.
- The team is now mining bacteriophage genomes for additional MurJ-inhibiting proteins, treating millions of years of viral evolution as a library of ready-made antibiotic strategies.
The bacteria killing people in hospitals and homes are becoming harder to stop. Tens of thousands die each year in the United States from infections that once yielded to a simple course of antibiotics, and the numbers are rising. Biochemist Bil Clemons and his colleagues at Caltech turned away from conventional chemistry and toward the natural world — specifically, toward the ancient rivalry between viruses and bacteria — in search of new answers.
At the heart of their inquiry is the bacterial cell wall, a rigid lattice of peptidoglycan that gives bacteria their structure and keeps them alive. Human cells have no such wall, which makes it an ideal target: a drug that disrupts peptidoglycan construction would kill bacteria while leaving human tissue unharmed. Three proteins — MraY, MurG, and MurJ — act as essential ferries in this construction process, shuttling raw materials across the bacterial membrane. If any one fails, the wall cannot be built and the bacterium dies. Yet no approved drug currently targets them.
The breakthrough came from studying bacteriophages, viruses that infect bacteria and must break through the peptidoglycan wall to escape and spread. Graduate student Yancheng Evelyn Li used high-resolution electron microscopy to examine proteins from three unrelated phages. Each protein, evolved independently, worked the same way: it bound to MurJ and locked it in place, preventing the molecular movement the protein needs to function. The cell wall could not be built. The bacterium died.
What moved the researchers most was the convergence itself. Three separate evolutionary lineages, with no connection to one another, had each arrived at the same solution and the same target. Clemons sees this not as coincidence but as a signal — evolution's own annotation marking where bacteria are most vulnerable. The team now plans to search phage genomes for more such proteins, treating millions of years of viral ingenuity as a guide for the next generation of antibiotics.
The bacteria that kill people are getting harder to kill. In hospitals and homes across America, infections that once responded to a course of antibiotics now shrug them off. Tens of thousands of people die each year from these resistant strains, and the death toll is climbing. Researchers at Caltech have begun looking for answers not in chemistry labs, but in the natural world—specifically, in the way viruses attack bacteria.
The problem is old. Bacteria evolve quickly, and they have been evolving resistance to our medicines almost as fast as we can make them. Bil Clemons, a biochemist at Caltech, puts it plainly: we now face bacteria resistant to everything in our arsenal. The solution, he and his colleagues believe, lies in finding new targets—weak points in bacterial biology that we haven't yet exploited.
One such weakness sits at the bacterial cell wall. All bacteria build these walls from a material called peptidoglycan, a rigid lattice that gives bacteria their shape and holds them together. Humans don't have peptidoglycan. Our cells are built differently. This difference is the key: a drug that attacks peptidoglycan production would kill bacteria while leaving human tissue untouched. Penicillin, discovered nearly a century ago, works this way. But bacteria have learned to resist it.
Three proteins—MraY, MurG, and MurJ—are essential to building the cell wall. They work like ferries, shuttling the raw materials of peptidoglycan across the bacterial membrane so construction can continue outside. If any one of these proteins stops working, the wall cannot be built, and the bacterium dies. Yet no approved drug currently targets them directly. Clemons and his team wondered why.
The answer came from an unexpected place: bacteriophages, viruses that infect bacteria. These tiny invaders face a problem of their own. To escape a bacterial cell and infect others, they must break through the peptidoglycan wall—a barrier as formidable as chainmail. Over millions of years, phages have evolved proteins that do exactly this. Yancheng Evelyn Li, a graduate student in Clemons's lab, decided to study how.
Using high-resolution electron microscopy, Li examined three different phage proteins, each from an unrelated virus, each evolved independently. All three worked the same way: they bound to MurJ and locked it in place. The protein, which normally flexes and shifts to move its cargo across the membrane, became frozen in a single position. Without that movement, the cell wall could not be built. The bacterium died.
What struck the researchers most was the convergence. Three separate viruses, with no evolutionary connection to each other, had each discovered the same solution to the same problem. They had all learned to target MurJ in nearly identical ways. This was not accident. This was evolution saying: this is the weak point. This is where bacteria break.
Clemons sees in this finding a roadmap. If evolution has identified MurJ as an ideal target, then medicine should follow. The team plans to search phage genomes for more proteins like these, hoping to unlock additional insights into how to kill resistant bacteria. The work appears in Nature, published in February 2026, and it represents a shift in thinking: sometimes the best antibiotics are not invented in laboratories, but discovered in the natural strategies that viruses have already perfected.
Citas Notables
Evolution is powerful, and in bacteria, resistance to antibiotics develops quickly. We now deal with bacteria resistant to all the medicines we have.— Bil Clemons, Caltech biochemist
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.— Bil Clemons
La Conversación del Hearth Otra perspectiva de la historia
Why does it matter that three unrelated viruses hit the same target?
Because it suggests that target is genuinely weak. If evolution independently arrived at the same solution three times, it's not luck—it's a signal that MurJ is where bacteria are vulnerable.
But we already knew MurJ was important. Why couldn't we just target it ourselves?
We didn't understand how to disable it without harming human cells. The phage proteins showed us the mechanism—they lock it in place. That's the insight we needed.
So you're saying we should copy what viruses do?
Exactly. Viruses have been running this experiment for billions of years. They've already solved the problem of killing bacteria. We're just learning to read their solutions.
How quickly could this become a drug?
That's the hard part. Understanding the mechanism is one thing. Turning it into a medicine that works in a human body is years of work. But at least now we know where to look.
What happens if bacteria evolve resistance to this too?
They might. But the more targets we have, the harder it is for them to resist all of them at once. And if we keep studying phages, we'll keep finding new targets.