Respiratory pathways of Rhodobacter sphaeroides 2.4.1(T): identification and characterization of genes encoding quinol oxidases

Rhodobacter sphaeroides 2.4.1(T) respires aerobically via a branched respir atory chain consisting of both cytochrome c oxidases and quinol oxidases. H ere, genes from chromosome II encoding two distinct quinol oxidases have be en characterized. The qoxBA genes encode a putative heme-copper quinol oxid ase, whereas the qxtAB genes encode a quinol oxidase homologous to the cyan ide-insensitive oxidase of Pseudomonas aeruginosa. No phenotype was observe d for mutations in either oxidase in the wild-type background. A strain con taining a qxtA mutation in a cytochrome bc(1) complex mutant background was unable to grow aerobically. No role was found for the Qox oxidase, nor was a qoxB::lacZ transcriptional fusion expressed under a variety of condition s. These are the first molecular studies to characterize the quinol oxidase s of R. sphaeroides 2.4.1(T). (C) 2000 Federation of European Microbiologic al Societies. Published by Elsevier Science B.V. All rights reserved.