BOB HIRSHON (host):
Disease-fighting bacteria. I’m Bob Hirshon and this is Science Update.
Toxoplasma gondi is a parasite that can kill developing fetuses. Fortunately, such infections are rare—even though the human immune system has no ability to detect the parasite. Recently, scientists discovered that a friendly bacterium living in the gut acts as a kind of watchdog. It releases a chemical signal when it runs across the parasite, telling the human immune system to come and fight it off.
In other news, tiny, leaf-eating aphids are parasitized by wasps that lay their eggs in them. But aphids infected with a particular bacterium are spared. Now scientists find that a virus that lives in the bacterium that lives in the aphid is responsible. The virus infects wasps; somehow wasps can tell if aphids have the virus, and avoid them like the plague. I’m Bob Hirshon for AAAS, the Science Society.