Leave water in contact with metal for any length of time and you've got a problem. Slimy bacterial colonies, or biofilms, form on just about any surface under water and corrode metal surfaces. One kind of sulfate-reducing bacteria can cause pitting even on stainless steel. But researchers at the Electric Power Research Institute (EPRI) in Palo Alto, Calif., have found that certain bacteria actually inhibit corrosion. These "aerobic" species not only consume the oxygen that corrodes metal; they also secrete proteins that suppress bacterial growth.

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