GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

15. ELECTRON TRANSPORT UNDER ANAEROBIC CONDITIONS (ANAEROBIC RESPIRATION)

Electron transport-coupled phosphorylation in aerobic microorganisms yields significantly more ATP than substrate-level phosphorylation, which occurs during Fermentation. It is therefore not surprising that evolution favored a metabolic pathway in which hydrogen from an organic substrate is transferred to "bound" oxygen (such as nitrate, sulfate, carbonate, etc.), reducing these compounds with substrate hydrogen. The ability to transfer electrons to such compounds enables Bacteria to oxidize substrates without molecular oxygen and harvest more energy than is possible via fermentation.

Such bacteria possess an electron transport system and contain Cytochromes. Energy generation via phosphorylation coupled with electron transport to terminal acceptors like nitrate or sulfate is termed Anaerobic Respiration. Depending on The Nature of the inorganic hydrogen acceptor, nitrate, sulfate, carbonate, and Other types of respiration are distinguished (Fig. 15.1).

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Fig. 15.1. Energy generation processes via Oxidative Phosphorylation under aerobic and anaerobic conditions

(aerobic and anaerobic respiration)