Nitrogen is an essential component of life. For example, it is required for the production of proteins. Boran Kartal, head of the Microbial Physiology group at the Max Planck Institute for Marine Microbiology in Bremen, studies nitrogen-cycling microorganisms, which control the bioavailability of this vital resource. A particularly interesting part of the nitrogen cycle is the anammox process, short for anaerobic ammonium oxidation. Here, nitrite or nitric oxide and ammonium are converted directly into dinitrogen gas. Now Kartal and his colleagues discovered a protein involved in the anammox process that might have some surprises. Their results are published in the November issue of Journal of Biological Chemistry.