Oxidative Phosphorylation in Bacteria which Contain Different Cytochrome Oxidases

Abstract

The oxidative phosphorylation efficiencies of seven species of bacteria, selected on the basis of their cytochrome oxidase composition, were determined from measurements of growth efficiencies with respect to oxygen (YO2) and →H+/O quotients of washed cell suspensions. Organisms which contained either cytochrome oxidase aa3 (Bacillus subtilis, Microbacterium thermosphactum) or o (Xanthomonas hyacynthi, Acinetobacter lwoffi, Escherichia coli and Kurthia zopfii) as their sole terminal oxidase exhibited P/O ratios of approximately 3 whereas Acetobacter T71, which contained cytochrome oxidase a1, as its major oxidase, exhibited a P/O ratio of approximately 1. The synthesis of cytochrome oxidases a1, and a2 by E. coli under oxygen‐limited conditions was accompanied by a sharp decrease in whole‐cell energy‐conversation efficiency. A similar decrease in efficiency was also observed as a result of the increased use by K. zopfii of a second oxidase, insensitive to cyanide and carbon monoxide, which has not hitherto been reported. The possibility that the different cytochrome oxidases may terminate respiratory chains of different redox span or may be associated with separate phosphorylating or non‐phosphorylating chains is discussed in relation to the general properties and physiological functions of these oxidases. Copyright © 1973, Wiley Blackwell. All rights reserved