Its founders made a salmon burger. Their customers wanted bacon. Now Prime Roots is growing fungi into deli meats - and betting that a familiar sandwich can sell an unfamiliar ingredient.

A beach encounter led a former packaging executive to a Yellowstone microbe, an old Chicago stockyard and a larger question: how much food can we make with much less?
A geomicrobiologist scooped a strange fungus out of a Yellowstone hot spring. A decade and half a billion dollars later, it is being sold as cream cheese, yogurt and breakfast patties.