Energy metabolism and practical implications
Biological treatments of solid waste

The energy metabolism of all living organisms is based on redox reactions. This means that living organisms extract the energy they need to sustain life by oxidizing substrates (referred to as electron and proton donors) and reducing one or more acceptors. The energy they withdraw is proportional to the potential difference between the "donor" and "acceptor" pairs. Due to the wide variety of environmental conditions found in the planet's different biotopes, the microbial world is highly diversified, with vast metabolic capacities. Many substances can be used by microorganisms as electron-donating substrates and as final electron acceptors