Energetic efficiency of Escherichia coli: effects of mutations in components of the aerobic respiratory chain

Abstract

The aerobic respiratory chain of Escherichia coli can function with either of two different membrane-bound NADH dehydrogenases (NDH-1 and NDH-2) and with either of two ubiquinol oxidases (bd-type and bo-type). The amounts of each of these enzymes present in the E. coli membrane depend on growth conditions in general and particularly on the dissolved oxygen concentration. Previous in vitro studies have established that NDH-1 and NDH-2 differ in the extent to which they are coupled to the generation of an energy-conserving proton motive force. The same is true for the two ubiquinol oxidases. Hence, the bioenergetic efficiency of the aerobic respiratory chain must depend on the electron flux through each of the specific enzyme components which are being utilized. In this work, the specific rates of oxygen consumption for cells growing under glucose-limited conditions are reported for a series of isogenic strains in which one or more respiratory components are genetically eliminated. The results are compatible with the proton translocation values of the various components reported from in vitro measurements. The data show that (i) the bd-type oxidase is less efficient than is the bo-type oxidase, but the former is still a coupling site in the respiratory chain; and (ii) under the conditions employed, the wild-type strain uses both the NDH-1 and NDH-2 NADH dehydrogenases to a significant degree, but most of the electron flux is directed through the bo-type oxidase.

Demonstration of separate genetic loci encoding distinct membrane-bound respiratory NADH dehydrogenases in Escherichia coli

“…Simultaneous alterations in the levels of NADH dehydrogenases and of the terminal oxidases would allow the cell to tune the oxidation of substrates to a wide range of H' translocated per NADH oxidized. Studies of the relative bioenergetic efficiencies of these enzymes in vivo are consistent with in vitro results (6).…”

Role of Cytochrome bd Oxidase from Corynebacterium glutamicum in Growth and Lysine Production

“…Although inhibitory effects due to the overproduction of four membrane proteins cannot be excluded, the more likely reason for the reduced growth is the difference in bioenergetic efficiency between the cytochrome bc 1 -aa 3 supercomplex and cytochrome bd oxidase (6). As outlined previously (3), the former pathway should couple transport of two electrons from menaquinol to oxygen to the transfer of six protons from the cytoplasm to the outside, whereas the latter pathway can transfer only two protons to the outside per two electrons transported to oxygen (20,28) (Fig.…”

Precise determinations of C and D periods by flow cytometry in Escherichia coli K-12 and B/r

“…To obtain faster growth Casamino acids or amino acid mixtures were added, or the cultures were grown in buffered LB medium (Miller, 1972) with 0?2 % glucose. Chemostat cultures were grown exactly as described by Calhoun et al (1993) except that the glucose input was 2 g l 21 instead of 5 g l 21 . The glucose concentrations were measured immediately after sampling and were found to be not detectable, which is compatible with the Regine Hengge-Aronis, Freie Universität Berlin FH1674 trp-3 his-4 thi-1 galK2 lacY1 or lacZ4 mtl-1 ara-9 tsx-3 ton-1 rpsL8 or rpsL9 supE44 pyrB (Tn5 near pyrB) dnaA606…”