This lecture covers the processes of nitrification and anammox, which involve the oxidation of ammonium under different conditions. It explains the steps of ammonia and nitrite oxidation, electron transfer mechanisms, and the role of specific enzymes. Additionally, it delves into the biochemistry of anammox, focusing on hydrazine synthesis and electron transport chain. The lecture also discusses the significance of nitrification in nutrient cycling and the importance of anammox in ammonia-rich environments like wastewater treatment.