Precursors to Modern Aerobic Ammonium Oxidation: Oxygenic and Electrogenic Anaerobic Pathways

How did microbes evolve to use O2? How did O2-dependent pathways derive from or evolve under anoxic conditions? Thiscentral evolutionary mystery remains essentially unresolved. it is possible to identify the evolutionary history ofmodern aerobic pathways by discovering the vestiges of ancient anaerobic pathways (AnPs) that persist in modernmicrobes. Aerobic nitrifiers contain aerobic metabolisms, while few clues, such as chlorite dismutase enzyme in Nitrospira,NO dismutase enzyme in Methylomirabilis and electrochemical signals from aerobic nitrifiers support the notion thatremnants of AnPs remain. Hence, this project postulates that in nitrifiers currently considered strict aerobes, we can identify the vestigesand integral remains of the earliest aerobic pathways: we will identify the AnPs of NH4+ oxidation that is driven by respiration mediated by EET.