May 27, 2009

Study finds yeast has full sexual cycle

U.S. scientists say an emerging form of the pathogenic yeast Candida can complete a full sexual cycle in a test tube, even while missing reproduction genes.

Sex contributes to the Candida yeast species' evolutionary success, said Dr. Joseph Heitman, director of the Center for Microbial Pathogenesis at Duke University. I think the fact it has a complete sex cycle is likely to play a role in the evolution of drug resistance in this emerging pathogenic yeast species.

Humans are susceptible to three types of Candida infection: thrush (in the mouth and throat), vaginal infection and a sometimes fatal systemic infection of bloodstream and organs, such as the kidney.

In a paper published May 24 online in the journal Nature, Heitman's team reports eight Candida species have a sexual cycle missing many genes related to reproduction found in other species.

With co-author Anna Floyd, Heitman and Dr. Jennifer Reedy explored the question further in a study appearing in the May 14 issue of the journal Current Biology.

The most important finding was that yeast can complete a full sexual cycle, i.e., reproduce, without the genes previously thought to be necessary for reproduction.

What we found is that the sexual cycle has a new way to create genetic diversity, and it provides a unique vantage point from which we can explore the mechanisms of sexual reproduction, Reedy said.