The Smell of Bacteria Warfare

Even before the flowers bloom, the scent of spring fills the air.

Beneath our feet, countless microbes called Streptomyces release chemicals as they awaken and warm up this season. “One of these chemicals is geosmin, which is responsible for the earthy smell of the soil in the spring,” said Susan Perkins, a microbiologist at the American Museum of Natural History.

Streptomyces bacteria spew geosmin as a weapon against other bacteria in the soil where they live. But to us, that chemical produces a distinct smell known aspetrichor, which we recognize as the earthy scent following a rainstorm.

“If you had a colony of Streptomyces in a petri dish and you opened the lid, you’d swear you had your nose in a flower pot,” Dr. Perkins said.

I wonder what soil would smell like without geosmin.