This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The toxin NheABC, produced by Bacillus cereus, is particularly active in the pH conditions found in open wounds. Researchers at Umeå University found that the toxin damages both cell membranes and mitochondria and helps the bacterium establish infection in wounded tissue.
"Our findings strengthen the view that disease-causing bacteria within the B. cereus group detected in deep or infected wounds should not always be dismissed as harmless contamination," says Abdelbasset Yabrag, a Ph.D. student at the Department of Molecular Biology, Umeå University, and one of the study's two first authors. Bacteria belonging to the B. cereus group are found almost everywhere, including in soil, dust and food, and are best known for causing food poisoning. The same group of bacteria can also cause serious infections outside the gastrointestinal tract, including in open wounds.
However, it has so far remained unclear which factors enable these bacteria to cause such damage. The researchers showed that the NheABC toxin makes small holes in cell membranes and causes significant damage to mitochondria. Experiments using artificial membranes revealed that certain lipids in mitochondria, such as cardiolipin, enhance the damaging effects of the toxin.
The paper is published in the journal Cell Communication and Signaling. The study combined several experimental models, including human cells grown in two- and three-dimensional systems, laboratory-grown mini-guts (intestinal organoids), artificial cell membranes, advanced microscopy and a mouse model of wound infection. The most surprising finding concerned acidity.
The toxin's harmful activity was significantly lower under acidic conditions than at neutral or alkaline pH levels. Chronic wounds can develop a more alkaline environment due to the presence of blood, tissue fluids and metabolic byproducts such as ammonia. This may create conditions that favor bacterial growth and colonization.
In a mouse model of wound infection, NheABC contributed to increased bacterial colonization and a stronger local inflammatory response. This differs from the MakA toxin produced by the cholera-causing bacterium Vibrio cholerae, which the same research group has previously shown to be activated under acidic conditions. "If toxin activity depends on the surrounding environment, this could open up new ways of reducing tissue damage during infections.
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