Roland Piquepaille writes: "You probably think that scientists know everything about the common and essential vitamin B12, the only vitamin synthesized by soil microbes. In fact, one part of this biosynthesis has puzzled researchers for at least 50 years. But now, MIT and Harvard biologists have solved this vitamin puzzle by discovering that a single enzyme known as BluB synthesizes the vitamin. So what is the next challenge for the researchers? It's to discover why the soil microorganisms synthesize the vitamin B12 at all, because neither them — nor the plants they're attached to — need it to live. Read more for additional references and a picture of BluB."