SUMMARY: The effect of medium dissolved-oxygen tension on the molar growth yield, respiration and cytochrome content of in chemostat culture ( 0·37 hr) was examined. The molar growth yield (), the specific rate of oxygen (q) and glucose consumption, and the specific rate of carbon dioxide evolution were independent of the dissolved-oxygen tension above a critical value (< 2 mmHg). However, the potential respiration rate increased with reduction in the dissolved-oxygen tension at values of the dissolved-oxygen tension well above the critical value. Changes in the cytochrome content occurred at dissolved-oxygen tensions well above the critical value. An increase in cytochrome relative to cytochrome was observed as the dissolved-oxygen tension was decreased. Reduction of the dissolved-oxygen tension to less than 1 mmHg caused a switch to fermentative metabolism shown by the apparent rise in and decrease in the molar growth yield from glucose. At this point the potential respiration rate ( ) increased to its highest value, while the cytochrome pattern reverted to that observed at dissolved-oxygen tensions above 96 mmHg. There appeared to be no correlation between cytochrome content, potential , , and cyanide sensitivity of the organism at various dissolved-oxygen tensions.


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