Cell Biology, Biochemistry and Metabolism of Unique Anammox Bacteria

Anaerobic ammonium oxidation (anammox) bacteria oxidize ammonium in the absence of oxygen with NO2 as the oxidant instead of oxygen and form dinitrogen (N2) as the end product. Anammox bacteria belong to the phylum Planctomycetes. Anammox bacteria are characterized by a compartmentalized cell architecture featuring a central cell compartment, the “anammoxosome”. This organelle is surrounded by ladderane lipids, which make the organelle nearly impermeable to hydrazine and protons. Anammox bacteria show similarities to both Archaea and Eukarya, making them extremely interesting from a cell biological perspective. Anammox metabolism takes place in a special and unique cell organelle, the anammoxosome. Here, energy released in the anammox reaction is used to generate proton-motive force that drives ATP synthesis. This respiratory process is supported by novel membrane-bound protein complexes. On a global scale, anammox bacteria significantly contribute to the removal of fixed nitrogen from the environment and the process is finding rapidly increasing interest in wastewater treatment. This chapter highlights the current knowledge on the cell biology, biochemistry and metabolism of this unique group of bacteria.