RESPIRATORY CONTROL IN ESCHERICHIA-COLI K-12

Contrary to the generl view point that respiratory control does not exist in Escherichia coli, we have been able to demonstrate this phenomenon in this micro‐organism. E. coli cells growing aerobically on an oxidizable carbon source respire at a high rate, which cannot be increased by the addition of uncouplers of oxidative phosphorylation. Upon removal of the carbon source, the rate of respiration decreases progressively to reach, after 10 min, less that 1/20 of its previous value. Under these conditions the addition of an uncoupler increases the residual respiration by a factor of 3 to 9. This increase is due to the release of respiratory control. Release of respiratory control cannot be observed upon addition of ADP which does not penetrate across the membrane. Respiratory control can also be shown in the presence of non‐limiting respiratory substrate provided that it is not a carbon source. This was shown by measuring the rate of oxidation of ascorbate and phenazine methosulfate. NADH oxidase activity of membrane vesicles obtained by high pressure disintegration was increased by a factor of about 1.5 upon the addition of uncouplers and also upon addition of ADP plus phosphate. In contrast, membrane vesicles depleted from BF1 ATPase (a soluble bacterial coupling factor presenting ATPase activity) did not exhibit respiratory control. It could be restored either by rebinding of BF1 ATPase or by addition of dicyclohexylcarbodiimide, an ATPase inhibitor. Copyright © 1979, Wiley Blackwell. All rights reserved