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Waste Not

April 25, 2015

The bacterium, Crocosphaera watsonii (pictured), is one of the few marine microbes that can convert nitrogen gas into organic nitrogen, which acts as fertilizer to stimulate plant growth in the ocean, just as it does on land. But nitrogen conversion is itself limited by iron availability, which is needed for the enzymes that make organic nitrogen. As a result, C. watsonii survives by using a remarkable biochemical trick: It recycles iron. By day, it uses iron for photosynthesis to make carbohydrates; then by night, it appears to reuse the same iron in different enzymes to produce organic nitrogen.(Photo courtesy of John Waterbury and Freddy Valois, Woods Hole Oceanographic Institution)