Oxygen as Acceptor

Area of Science:

• Microbiology
• Biochemistry
• Molecular Biology

Background:

• Escherichia coli possesses a flexible respiratory chain adaptable to aerobic and anaerobic conditions.
• The bacterial respiratory chain involves dehydrogenases, a quinone pool, and terminal reductases.
• Aerobic respiration in E. coli utilizes two primary oxidoreductases: cytochrome bo₃ (cyoABCDE) and cytochrome bd (cydABX).

Purpose of the Study:

• To compare the effects of various inhibitors on the respiratory activities of cytochrome bo₃ and cytochrome bd in E. coli.
• To discuss the genetics and prosthetic groups of cytochrome bo₃ and cytochrome bd.
• To present novel data on the electrogenic function of the appBCX-encoded cytochrome bd-II.

Main Methods:

• Comparative analysis of inhibitor effects on enzyme activity.
• Review of existing literature on genetics and prosthetic groups.
• Presentation of new experimental data on cytochrome bd-II function.

Main Results:

• Detailed comparison of inhibitor sensitivities for cytochrome bo₃ and cytochrome bd.
• Updated information on subunit composition and stress resistance roles of cytochrome bd.
• Novel findings on the proton motive force generation by cytochrome bd-II.

Conclusions:

• Cytochrome bo₃ and cytochrome bd play distinct roles in E. coli aerobic respiration.
• Cytochrome bd contributes to bacterial resistance against nitrosative and oxidative stresses.
• Cytochrome bd-II is confirmed to be electrogenic, contributing to proton motive force generation.