The World’s Most Diverse Group of Bacteria Lives Inside Your Mouth | Popular Science

Jessica Mark Welch is an Associate Scientist at the Marine Biological Laboratory in Woods Hole. This is her story from the field as told to Claire Maldarelli.

Bacteria run the world, and even though they’re all around us and seemingly crucial to the function of every single biological ecosystem, we still know little about them. Understanding how a big and diverse population of microorganisms relates to itself and its environment—particularly how each one is distributed within the space it occupies—will help us better grasp the dynamics behind complex microbial networks affecting the well-being of all living creatures.

The human mouth is one of the most densely packed bacterial hot-spots anyone’s ever studied, so my colleagues and I scraped the tongues of 21 volunteers and placed the gunk onto microscope slides. Using data from the Human Microbiome Project, we identified the 17 most abundant kinds of bacteria and attached a dye that gave each one a different color when we shined a laser on them.

Feature photo: Micrograph showing Rothia cells (light blue) in their native habitat, a bacterial biofilm scraped from the human tongue. Credit: Jessica Mark Welch, Marine Biological Laboratory