Personal oral hygiene notwithstanding, your mouth is sloshing with hundreds of species of microorganisms. Most are harmless, but some can do real damage, such as causing periodontitis, in which the microbes that cause plaque get below the gum line, leading to inflammation and infection.

Researchers have had a tough time sorting out all of these small species—and how they interact. Now, a new multi-color fluorescent labeling technology has allowed microbiologists to peer into the human mouth's microscopic jungle and discover new dynamics among several key groups. The findings were presented Wednesday at the American Society for Cell Biology's annual meeting in Denver.

Combinatorial Labeling and Spectral Imaging (CLASI) was designed by a team at the Marine Biological Laboratory in Woods Hole, Mass., and Brown University in Providence, R.I., to distinguish microbes in the human body and in other complex communities in nature. Previous fluorescent labeling approaches relied on the classic green fluorescent protein, but CLASI allows for a range of colors by harnessing additional fluorescent proteins.

In one dental sample, the team characterized 15 taxa and assessed their density and spatial distribution. The researchers found that Actinomyces—known to cause oral infections—and Prevotella—tied to infections of the respiratory tract—were found in closest proximity to one another more often than other microbe pairs, thus likely playing a key role in the pesky biofilm we know as plaque.

With the help of new algorithms for tracking various color combos, the group now aims to pinpoint more than 100 mouth microbes in a single sample. The goal is to eventually profile the full 600-plus species found in our mouths.

Image: Spectral fluorescence image of 15 different species of human oral microbes grown in the laboratory and labeled with taxon specific probes in a CLASI-FISH experiment. Credit: Alex Valm