In most environments, ammonia (NH₃) is oxidized to nitrate (NO₃⁻) via the intermediate nitrite (NO₂⁻). This is a microbe-driven process involving phylogenetically distinct types of microorganisms, namely, ammonia-oxidizing bacteria (AOB) and Thaumarchaea (AOA), and nitrite-oxidizing bacteria (NOB). Nitrosomonas europaea and Nitrobacter winogradskyi are the best studied AOB and NOB, respectively,...