Question

Compare and contrast aerobic cellular respiration and fermentation in a facultative anaerobe such as Escherichia coli.

Answer 1

In E. coli, aerobic cellular respiration is preferred over fermentation. In aerobic cellular respiration, growth of E. coli is by oxidation of carbs like glucose and NAD, which reduces to NADH. NADH is an intermediate product, later on, serves as the electron donor for cellular respiration.

2 NADH + 2 H+ + O2  →  2 NAD+ + 2 H2O

Enzymes that are used in aerobic cellular respiration of E. coli are -

Cytochrome bo oxidase, Cytochrome bd-I oxidase, Cytochrome bd-II oxidase, NADH dehydrogenase I, NADH dehydrogenase II, Succinate dehydrogenase, L-lactate dehydrogenase, glycerol-phosphate dehydrogenase, and proline dehydrogenase.      

In anaerobic conditions and in the absence of alternative electron acceptors  E. coli prefers fermentation. the products of fermentation reaction are acetate, ethanol, acetate, and formate with smaller amounts of succinate. Also, hydrogen and carbon dioxide are produced. Further reaction depends on the pH of the environment and substrate of the fermentation.