Manganese: elemental defence for a life with oxygen.

The presence of enzymes such as catalase, peroxidase and superoxide dismutase (SOD) obviates the problems associated with life in an aerobic environment by eliminating the harmful reactive oxygen species (ROS) that arise from respiration. Enzymic detoxification of ROS might not, however, be the only mechanism at work in bacteria. The accumulation of manganese (Mn), an abundant element in many environments, via several, recently identified transporters is thought to form the basis for an alternative, catalytic detoxification of ROS. An increasing body of evidence from work on the genetics and biochemistry of Mn accumulation and its cellular roles reveals that this overlooked defence mechanism is likely to be widespread among bacteria and might also contribute to virulence.