[news.sciencemag.org]

"Most of the time, Candida is a peaceful passenger that lives with the other harmless microbes in our mouths, but when a person's immune system is compromised, the fungus can run rampant, causing a yeast infection in the mouth known as thrush. This infection is common in people with HIV, where it can make swallowing difficult and contribute to poor nutrition. Any difference in the mouth microbiomes of people with HIV and those without the virus could give scientists clues about how a healthy population of oral microbes might help keep Candida in check, says medical mycologist Mahmoud Ghannoum of Case Western Reserve University in Cleveland, Ohio. "If you have a disturbance in the community, you are likely to have disease."

So Ghannoum's group compared the microbes, both bacterial and fungal, in the mouths of 12 people with HIV and 12 healthy controls. One hypothesis holds that bacteria keep fungi in check, but Ghannoum's team didn't find any major differences between the bacterial populations in the two groups. The fungi, though, were a different story: Healthy people had more species of fungi in their mouths, and one particular fungus stood out as a possible competitor to Candida. Its name is Pichia."