The two faces of oxygen

Scientists have suspected for half a century that reactive oxygen species (ROS) are major instigators of aging. These byproducts of metabolism batter a wide variety of molecules within cells, and an organism's ability to repair the damage declines with age. Now, some researchers say they're wrapping up the case against ROS, at least for lower organisms. By counteracting this destruction with protective enzymes, researchers have extended the average lifetime of some invertebrates. But the verdict isn't in yet, because recent studies have revealed that ROS also make key contributions to normal cell signaling.