Iron-respiring microbes could have a role in sulfur cycling

A bacterium that uses sulfide as an energy source to metabolize solid iron oxides has been discovered, revealing a biological reaction that was previously assumed to be solely chemical. This finding uncovers a firm microbial link between sulfur and iron cycling in oxygen-free environments such as aquatic sediments. A species of bacteria grows when both ferrihydrite and sulfide are present, but not when either is absent.