Usually when you hear about the rapid evolution of bacteria, the story is typically some grim tale of antibiotic resistance or the emergence of some pathogen once restricted to animals. Here’s a nicer narrative, but no less instructive. In tomorrow’s New York Times I have an article about yogurt, and how the bacteria in its culture have been undergoing drastic genomic change since the stuff was invented some 5000 years ago.

I report on a new study on Lactobacillus bulgaricus, found in many yogurt cultures. (The paper comes out some time this week in PNAS.) The analysis, based on the microbe’s newly sequenced genome, suggests that the bacteria descend from microbes that originally fed on plants. Some of them