Staph bacteria are choosy about their iron source

Some people prefer to get their iron from spinach rather than from steak. Staphylococcus aureus, the bacterium that causes staph infections, also has a favored iron source, a new study reveals.

This bacterium needs iron for several life-sustaining processes, such as copying DNA or generating energy. Some animals take advantage of this requirement when they’re infected with the microbe and limit the free iron in their blood and tissue, a response known as nutritional immunity. Even so, resourceful staph bacteria often snag iron from either of two alternate sources: heme, the ring-shaped portion of oxygen-carrying proteins such as hemoglobin, or a blood serum protein called transferrin.

To determine whether S. aureus prefers one source to the other, Eric Skaar and his colleagues at the University of Chicago placed the bacteria in environments supplemented with heme and transferrin. Each compound was labeled with a different, readily detectable iron isotope. Later, when the scientists looked for these isotopes in microbes, they found that S. aureus had preferentially consumed heme.

The finding, which appears in the Sept. 10 Science, may lead to new antibiotics directed at the microbe’s heme uptake mechanism, according to Skaar. “This allows us to be more intelligent in the systems that we target to inhibit disease,” he says.

From the Nature Index

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