How bacterial warfare helps superbugs thrive

Harmful bacteria aren’t just passively resisting antibiotics but are getting stronger through constant battle with rival strains, new research has shown.

Scientists often warn that the overuse of antibiotics helps to create drug-resistant bacteria, but a new study by a collaboration of scientists at the University of Reading and the University of Oxford shows that harmful bacteria aren’t just passively resisting our drugs.

The research explains why some pathogens – bugs harmful to health – are able to spread so successfully, even in tough environments like the human gut, where competition for space and food is fierce.

To survive, many bacteria have evolved powerful “weapon” molecules that can kill or disable their rivals.

A study co-authored by DrConnor Sharp, lecturer in biomedical sciences at the University of Reading, published in Nature Communications, shows how strains of bacteria that cause disease arm themselves with tiny protein toxins, called bacteriocins, aimed at killing rival bacteria.

These toxins often combine with mobile packages of DNA called plasmids, bundled with genes for virulence and antibiotic resistance, creating a dangerous combination.

These weapons help shape which species dominate in a community of bacteria and are especially important for pathogens trying to invade places like the human gut, where resident microbes normally keep them in check. Carrying such weapons offers clear benefits, but not all bacteria are equally armed.

“Understanding the weapons and tactics of bacterial warfare could open new doors for treatment,” said DrSharp. “If scientists can show how to block bacteriocins or disrupt the plasmids that carry them, we could have an option to weaken pathogens before they cause harm.”

The secret weapons inside superbugs

The study focused on E. coli, a type of bacteria that includes both harmless gut residents and dangerous strains that can cause urinary tract infections and sepsis which can cause people to become seriously ill.

By analysing over 2,600 bacterial genomes, the team discovered that around one-quarter carried genes for bacteriocins, encoded on plasmids. These weapons appeared more often in disease-causing strains than in benign gut-associated strains.

These toxin-encoding plasmids move easily between bacteria. The team uncovered evidence of frequent gene transfer, even between E.coli and Salmonella, suggesting bacterial warfare can escalate across species boundaries.

Even a single genetic swap can turn an ordinary microbe into a well-armed invader.

Some bacteriocins target iron uptake systems, critical for survival in the iron-poor environment of the human body. By knocking out competitors and monopolising resources, these pathogens can gain a powerful foothold.

“Antimicrobial resistance is a growing global health problem, causing millions of deaths worldwide every year,” Dr Sharp said.

“Gaining insights into bacterial strategies helps us to see the problem differently and could lead to new treatments other than just changing the types and frequency of drugs that doctors prescribe to fight infections.”

Full reference:

Sharp, C. and Foster, K.R. (2025) Bacterial warfare is associated with virulence and antimicrobial resistance. Nature Communications, 16, 9329, https://doi.org/10.1038/s41467-025-64363-5.