To rebalance the oral microbiome and cure chronic bad breath, researchers at the University of Washington are embarking on a first-of-its-kind experiment. Credit: iStock The human mouth is full of wonders. It’s home to hundreds of species of bacteria, fungi, viruses and protozoa, which work in delicate harmony to maintain our oral health. Sometimes, though, this complex system — known as the oral microbiome — can fall out of balance.