Fourteen years ago, the world’s largest bacterium, Thiomargarita namibiensis
, was discovered off the coast of Namibia. Since then we learned that the “Namibian sulfur pearl” has many close relatives in other parts of the sea and that it also plays an important ecological role: These bacteria can induce the formation of phosphorus-rich rocks. This process decreases the total amount of phosphate in seawater with the result that this nutrient becomes unavailable for other organisms. Thereby, the formation of these rocks counteracts the eutrophication of the ocean with respect to phosphate.