How a Deadly Yeast Balances Its Own Toxin to Survive in Your Mouth

A common yeast found in the human body relies on a carefully balanced toxin to survive in the mouth. Candida albicans, usually harmless, produces a substance called candidalysin to anchor itself without provoking a strong immune reaction. Too much of this toxin, however, can lead to inflammation and infection, researchers have discovered. Candida albicans is a yeast that naturally lives in the human microbiome. In the mouth, it uses candidalysin to colonise the mucous membrane, but only in small, controlled amounts. When levels rise too high, the immune system reacts, causing potential harm.

The toxin plays a dual role: it helps the fungus stay attached to oral tissues while keeping the body's defences in check. Scientists found that the gene *EED1* regulates both the growth of *Candida*'s hyphal form and the production of candidalysin. In this elongated state, the yeast releases the toxin, which directly damages host cells. Researchers noted that candidalysin has been preserved through evolution, allowing the fungus to persist in the mouth. The study highlights its importance in colonisation, though the exact mechanisms controlling its levels remain unclear. Previous work has linked the toxin to infections in other body regions, such as the vagina and intestines, but oral regulation differs.

The findings show how Candida albicans balances candidalysin to avoid detection while maintaining its presence. Too little prevents colonisation; too much triggers harmful immune responses. Understanding this process could help prevent infections caused by the yeast.