Experts at Newcastle University have collaborated with a team from the University of Dundee and found that toxins delivered by ‘poisoned arrows’ are used to kill off different kinds of cells that pose a threat to aggressive bacteria.

Using a weapon known as the Type VI secretion system to fire toxic proteins into neighbouring cells, the process allows competing bacteria to eliminate bacterial rivals. However, the teams discovered that the same process is used to attack fungal cells in mixed microbial communities.

Targeting fungal cells

The research, published in the journal Nature Microbiology, could pave the way for further research into targeting fungal cells that cause infections in humans.

Dr Katharina Trunk, from the Institute for Cell and Molecular Biosciences, Newcastle University, is first author of the study.

She said: “We don’t know whether the bacterium knows what it is fighting against, but it is clear that bacteria have a range of toxins that will kill other bacteria or fungal cells, allowing them to target a broader range of enemies than we previously thought.

“Microbes which can be killed by this bacterial weapon include fungi like Candida albicans, which can commonly cause infections in humans.

“We hope that a better understanding of how microbes kill each other will help find drug targets to develop new antimicrobial therapies.”

The work of the University of Dundee research team was funded by the Wellcome Trust and the Medical Research Council and involved collaboration with the researchers Dr Henrik Strahl, Professor Janet Quinn and the proteomics group of Professor Matthias Trost at Newcastle University.

Dr Sarah Coulthurst, from the University of Dundee School’s Division of Molecular Microbiology, said: “Bacteria kill one another because they want the space to grow and dominate.

“It’s been known for a while now that bacteria use the Type VI secretion system to do this, a bit like shooting poison arrows at a rival, but this research has revealed that bacteria is also using the same method against microbial fungi. It’s constant warfare.

“We don’t know whether the bacterium knows what it is fighting against, but it is clear that bacteria have a range of toxins that will kill other bacteria or fungal cells, allowing them to target a broader range of enemies than we previously thought.

“Microbes which can be killed by this bacterial weapon include fungi like Candida albicans, which can commonly cause infections in humans, so understanding how bacteria attack these could be beneficial in developing treatments for such conditions.

“Our long-term hope is that we can develop new ways to kill or counteract harmful microbes by learning from how they do it to each other.”

Funded research

Dr Coulthurst said that the discovery would offer further insight into how mixed microbial communities functioned.

She added: “The Type VI system is an incredible weapon, with ‘crossbow-like’ firing events visible under the microscope, but it is not the only system used by bacteria to compete against one another. For example, the majority of antibiotics in use today originally came from chemicals made by microbes competing against each other in soil communities.

“By learning more about how bacteria normally compete with each other and fungal cells, we can use that knowledge to our advantage.”

Press release adapted with thanks to the University of Dundee