05.30.06
Yogurt
About 5,000 years ago, cattle herders discovered how to make yogurt. Scientists are now discovering that they also mounted an unplanned experiment in evolution.
Certain species of bacteria are responsible for turning milk into yogurt. As the microbes feed on sugar in the milk, they produce acidic wastes that cause the milk to clot. They also make the yogurt uninhabitable for other bacteria, preventing it from spoiling. And by breaking down some milk proteins into smaller pieces, they give yogurt its distinctive flavor.
Americans bought 2.7 billion pounds of yogurt in 2004. To better understand the bacteria that drive that business, scientists have begun sequencing their genomes. A team of French scientists published the genome of a common inhabitant of yogurt, Lactobacillus bulgaricus. Their research appears in the current Proceedings of the National Academy of Sciences.