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'Dynamic duo’ defences in bacteria ward off viral threats

Southampton researchers have discovered that bacteria can pair up to fight off viruses together.

The new study found that bacterial cells can combine their strengths to combat attacks from phage viruses.

The understanding could help tackle antimicrobial resistance and lead to the development of new alternatives to antibiotics.

Dr Franklin Nobrega from the University of Southampton led the study. He is part of the NIHR Southampton Biomedical Research Centre (BRC). Findings have been published in the journal Cell Host & Microbe.

Working together

Phage viruses, or bacteriophages, could be thought of as ‘the good guys’ of the virus world. Spider-like in appearance, they kill harmful bacteria without affecting the good bacteria in our bodies.

Knowing how bacteria respond to phages is important for understanding how these viruses can be used to fight infections in humans.

Dr Nobrega, part of our BRC’s Microbiology, Immunology and Infection theme, said:

“Just like how our immune system protects us from harmful germs, bacteria have their own set of defence systems which create a dynamic shield against viral threats.

“Imagine if your white blood cells, antibodies, and killer T-cells all joined forces to fight off a virus together. This is exactly what is happening inside bacterial cells.”

He added: “We used to think of bacterial defence as a solo act, but it turns out it’s more like a buddy system. A ‘dynamic duo’ of defence systems merge their powers to mount a stronger response, potentially saving the cell from destruction.”

Data analysis

The researchers analysed existing datasets to find patterns of paired defence systems in the genomes (cell DNA instructions) of some 42,000 bacteria, including E. coli. They looked for pairs which occurred more often than would be expected by random chance.

The scientists then took a selection of these and tested them in the lab for enhanced virus immunity. They also looked for ‘synergy’ - a defence effect in the bacteria which is more powerful than the sum of its parts.

Further testing revealed for the first time how the partnerships between individual bacterial defences are based on one system using a function from another to improve its activity. Combined, they have a stronger effect than apart.

A global threat

The NIHR Southampton BRC is driving research to address the global challenge of antimicrobial resistance (AMR). This is where bacteria, viruses, fungi and parasites change over time and no longer respond to medicines, making infections much harder to treat.

Resistance to treatments can occur naturally. However, the overuse of certain drugs and poor infection control are accelerating the problem.

Phages offer a potential solution to overcoming AMR. Their ability to selectively target bacteria makes them a strong contender as an alternative to antibiotics. However, more research is needed before treatments can be widely used.

Dr Nobrega said: “Phages are already in use as a last-resort treatment for antibiotic-resistant bacterial infections. This is a practice known as phage therapy.

“But by delving into how bacteria defend against these phages, we can supercharge our strategies to make them even more effective at wiping out bacterial cells. This offers a glimmer of hope in the battle to keep infections at bay.”

The scientists say their research will complement efforts to develop phage therapy further.

The funding for this study was from the Wessex Medical Trust and the National Institutes of Health, USA.


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