Bacteria are among the most diverse organisms with respect to the types of enzymes they contain. You will be using some of the more common biochemical tests in the identification of your unknown. A variety of specialized media are designed to facilitate determining the biochemical reactions of bacteria. Most bacteria obtain energy from the oxidation of organic compounds such as sugars. Strict aerobes oxidize sugars to carbon dioxide and water through the process of aerobic respiration, using a cytochrome electron transport system and molecular oxygen as the final electron acceptor.
Many strict anaerobes perform fermentation reactions.
No cytochrome system is used in fermentations and oxygen is not involved. Fermentation is not as efficient an energy-yielding process as aerobic respiration. Facultative anaerobes possess the enzymes that allow them to perform either respiration or fermentation depending upon the availablility of oxygen. The types of compounds that an organism can ferment and the end products that are produced are genetically determined. Among the end products commonly generated by fermentation are organic acids and gases such as carbon dioxide and hydrogen.