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OXIDATION-REDUCTION EQUILIBRIA IN BIOLOGICAL SYSTEMS : II. POTENTIALS OF AEROBIC CULTURES OF B. TYPHOSUS
1Department of Bacteriology, College of Physicians and Surgeons, Columbia University, New York.
The Journal of Experimental Medicine
|October 30, 2009
Summary
Bacterial respiration in cultures of B. typhosus initially reduces oxygen, establishing medium potentials. Later, bacterial dissolution releases reductive substances, further lowering electrode potentials, especially with dextrose.
Area of Science:
- Microbiology
- Biochemistry
- Electrochemistry
Background:
- Reduction potentials in bacterial cultures are influenced by oxygen availability and bacterial metabolic activity.
- Understanding these potentials is crucial for characterizing bacterial environments and metabolic processes.
Purpose of the Study:
- To investigate the influence of B. typhosus on reduction potentials in culture media.
- To elucidate the mechanisms driving changes in electrode potentials during bacterial growth and death.
- To determine the role of bacterial respiration and cellular components in establishing redox states.
Main Methods:
- Measurement of electrode potentials (Eh) in B. typhosus cultures under varying oxygen conditions (atmospheric, deaerated, continuous oxygen flow).
- Incubation of cultures in different media (bouillon, dextrose-supplemented medium) over extended periods (up to 48 hours).
- Correlation of potential changes with bacterial growth, multiplication, and death rates.
Main Results:
- B. typhosus cultures initially showed a negative drift in Eh, reaching sterile deaerated levels (-0.085 to -0.095 V at pH 7.6) due to oxygen depletion.
- A further decline to more negative potentials (-0.145 V) occurred during bacterial decline, suggesting the release of reductive substances from cell dissolution.
- Dextrose supplementation accelerated this decline, while continuous oxygen supply prevented potential drift, highlighting the role of oxygen removal by respiration.
Conclusions:
- Bacterial respiration is key to establishing characteristic reduction potentials by consuming oxygen.
- Bacterial cell lysis releases reductive substances that contribute to more negative potentials, particularly evident when growth outpaces death.
- The presence of oxygen negates the influence of bacterial-derived reductive substances on electrode potentials.
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