![]() toluene) as a carbon source, there is significant interest in using these organisms as bioremediation agents in ferric iron contaminated aquifers. metallireducens) can use toxic hydrocarbons ( e.g. Since some ferric iron-reducing bacteria ( e.g.G. Electron flow in these organisms is similar to those in electron transport, ending in oxygen or nitrate, except that in ferric iron-reducing organisms the final enzyme in this system is a ferric iron reductase. Others, such as certain Desulfovibrio species, are capable of sulfur disproportionation (splitting one compound into an electron donor and an electron acceptor) using elemental sulfur (S0), sulfite (SO 3 −2), and thiosulfate (S 2O 3 2-) to produce both hydrogen sulfide (H 2S) and sulfate (SO 2−).Īcetogenesis is a type of microbial metabolism that uses hydrogen (H 2) as an electron donor and carbon dioxide (CO 2) as an electron acceptor to produce acetate, the same electron donors and acceptors used in methanogenesis.įerric iron (Fe 3+) is a widespread anaerobic terminal electron acceptor used by both autotrophic and heterotrophic organisms. Some unusual autotrophic sulfate-reducing bacteria, such as Desulfotignum phosphitoxidans, can use phosphite (HPO 3 –) as an electron donor. Sulfate reduction requires the use of electron donors, such as the carbon compounds lactate and pyruvate (organotrophic reducers), or hydrogen gas (lithotrophic reducers). It is also used in Gram-positive organisms related to Desulfotomaculum or the archaeon Archaeoglobus. Sulfate reduction is a relatively energetically poor process, and is used by many Gram negative bacteria found within the δ-Proteobacteria. Sulfate reduction uses sulfate (SO 2 −4) as the electron acceptor, producing hydrogen sulfide (H 2S) as a metabolic end product. Many denitrifying bacteria can also use ferric iron (Fe 3+) and different organic electron acceptors. This process is widespread, and used by many members of Proteobacteria. Nitrate, like oxygen, has a high reduction potential. Denitrification is the utilization of nitrate (NO 3 −) as the terminal electron acceptor. Many different types of electron acceptors may be used for anaerobic respiration. Figure: Anaerobic Respiration: A molecule other than oxygen is used as the terminal electron acceptor in anaerobic respiration. These molecules have a lower reduction potential than oxygen thus, less energy is formed per molecule of glucose in anaerobic versus aerobic conditions. Instead, molecules such as sulfate (SO 4 2-), nitrate (NO 3 –), or sulfur (S) are used as electron acceptors. This method still incorporates the respiratory electron transport chain, but without using oxygen as the terminal electron acceptor. anaerobic respiration: metabolic reactions and processes that take place in the cells of organisms that use electron acceptors other than oxygenĪnaerobic respiration is the formation of ATP without oxygen. ![]() reduction: A reaction in which electrons are gained and valence is reduced often by the removal of oxygen or the addition of hydrogen. ![]()
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