Images reveal how bacteria form communities on the human tongue

Using a recently developed fluorescent imaging technique, researchers in the United States have developed high-resolution maps of microbial communities on the human tongue. The images, presented March 24 in the journal Cell Reports, reveal that microbial biofilms on the surface of the tongue have a complex, highly structured spatial organization.

"From detailed analysis of the structure, we can make inferences about the principles of community growth and organization," says senior author Gary Borisy, of the Forsyth Institute and the Harvard School of Dental Medicine. "Bacteria on the tongue are a lot more than just a random pile. They are more like an organ of our bodies."

The human oral microbiome is a complex ecosystem. The spatial organization of microbial communities in the mouth is affected by a variety of factors, including temperature, moisture, salivary flow, pH, oxygen, and the frequency of disturbances such as abrasion or oral hygiene.

In addition, microbes influence their neighbors by acting as sources and sinks of metabolites, nutrients, and inhibitory molecules such as hydrogen peroxide and antimicrobial peptides. By occupying space, microbes can physically exclude one another from desirable habitats, but their surfaces also present binding sites to which other microbes may adhere.

In the new study, the researchers used a technique called Combinatorial Labeling and Spectral Imaging – Fluorescence in situ Hybridization (CLASI-FISH), which was recently developed in the Borisy lab. This strategy involves labeling a given type of microorganism with multiple fluorophores, greatly expanding the number of different kinds of microbes that can be simultaneously identified and localized in a single field of view.