A magazine for friends of the Warren Alpert Medical School of Brown University.

Fungus Among Us


A ‘mutation hotspot’ allows a common yeast to adapt to different host environments.

The fungus Candida albicans is found in the gastrointestinal tract of about half of healthy adults with little if any effect, yet it also causes an oft-fatal blood infection among patients with compromised immune systems, including those with HIV/AIDS. New research from Brown helps show how this common yeast gets the flexibility to live in these vastly different environments.

The researchers found that patient samples of the fungus frequently lack one copy of a gene that serves as a vital master regulator. In the lab, these cells can regularly switch to having a different phenotype by losing the other copy. Cells with one or two copies of the master regulator appear white in color and are more virulent in blood infections, while cells lacking both copies produce “gray” colonies that can predominate in the gastrointestinal tract.  

“Diversity in a microbial species protects them against changes in their environment,” says Richard Bennett, a professor of biology. “If they have diversity, a subpopulation of cells may be able to adapt, even if the rest of the population cannot. We found that some samples of Candida albicans can switch phenotype because they’re already carrying one inactivated copy of a gene in this genetic hotspot.” 

The study was published on Tuesday, Feb. 26, in the journal Cell Host & Microbe.

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