The Forest In Your Mouth

Ed Yong in Not Exactly Rocket Science:

The study of the human microbiome—the booming and much-hyped quest to understand the microbes that share our bodies—began in the mouth. Specifically, it began with dental plaque.

In 1683, Antony van Leeuwenhoek, the first human ever to see bacteria, became the first human ever to see his own bacteria. Untrained as a scholar but insatiably curious, he removed some of the thick plaque at the bottom of his teeth and examined it with his own hand-crafted microscopes. He saw multitudes of living things, “very prettily a-moving”, from spheres that spun like a top to rods that darted through water like fish. Enthralled, he soon started collecting plaque from the local citizenry and finding similar microbes within.

Mouth microbes were largely ignored for the next two centuries, until an American dentist named Joseph Appleton took an interest in them. Compared to microbes in the gut or skin, those in the mouth were easier to collect and less vulnerable to oxgyen. Between the 1920s and 1950s, Appleton and others catalogued these bacteria, and noted that how they were influenced by saliva, food, age, seasons, and diseases. Science historian Funke Sangodeyi notes that these efforts helped to turn dentistry—itself a marginalised part of medicine—into a true science rather than just a technical profession.

More here.