Acetic acid bacteria energy generation

Figure 19.3 Energy generation in acetic acid bacteria. The oxidation of ethanol leads to the release of electrons captured by quinones (QH2) in the plasma membrane of acetic acid bacteria. The transfer of electrons within the membrane can be nsed for tbe release of protons from integral membrane dehydrogenases or from membrane-associated dehydrogenases. The removal of protons by the quinol oxidases from the membrane creates a protomnotive force that can be used in the generation of ATP.

Compounds such as ethanol and acetic acid, which generally make stressors for bacterial cells, become abundant around cells as acetic acid fermentation proceeds. Furthermore, increases in temperature also occur from the heat generated by fermentation. Thus, acetic acid bacteria are constantly and inevitably exposed to various stressors during fermentation to acquire energy. To tolerate and thrive under such circumstances, acetic acid bacteria have acquired the ability to resist these stressors. 

Dissimilatory sulfate reducers such as Desul-fovibrio derive their energy from the anaerobic oxidation of organic compounds such as lactic acid and acetic acid. Sulfate is reduced and large amounts of hydrogen sulfide are generated in this process. The black sediments of aquatic habitats that smell of sulfide are due to the activities of these bacteria. The black coloration is caused by the formation of metal sulfides, primarily iron sulfide. These bacteria are especially important in marine habitats because of the high concentrations of sulfate that exists there. 

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