It’s almost like a new organism—a superorganism—with new functions.” Better (or worse) together In the past, Koo’s lab has focused on the dental biofilm, or plaque, present in children with severe tooth decay, discovering that both bacteria—Streptococcus mutans—and fungi—Candida albicans—contribute to the disease.Caries, commonly known as cavities, arise when sugars in the diet linger to feed bacteria and fungi in the mouth, leading to acid-producing dental plaque that destroys enamel.The new set of discoveries came about when Zhi Ren, a postdoctoral fellow in Koo’s group, was using microscopy that allows scientists to visualize the behavior of living microbes in real time.Next the team tested the properties of these cross-kingdom assemblages once they had colonized the tooth surface and found “surprising behaviors and emergent properties,” says Ren, “including enhanced surface adhesion, making them very sticky, and increased mechanical and antimicrobial tolerance, making them tough to remove or kill.” Perhaps the most intriguing characteristic of the assemblages, the researchers say, was their mobility.For example, tree frogs and grasshoppers can leap forward about 50 times and 20 times their own body length, respectively.” Although the exact mechanisms are unknown, the assemblages’ ability to “move as they grow,” the researchers say, has one clear consequence: It enables them to quickly colonize and spread to new surfaces."