• Pseudomonas aeruginosa;
  • Respiration;
  • Cytochrome;
  • Cytochrome oxidase;
  • Haem

Abstract Using transposon mutagenesis and screening for the loss of the ability to oxidise the artificial electron donor N,N,N′,N′-tetrarnethyl-p-phenylenediarnine, we have isolated a mutant of Pseudomonas aeruginosa that lacks all c-type cytochromes. This mutant is unable to grow anaerobically with nitrate as a terminal electron acceptor. Analysis of its respiratory function indicates that the mutant has lost its cytochrome c oxidase-terminated respiratory pathway but the cyanide-insensitive oxidase-terminated branch remains functional. Complementation of the mutant by in vivo cloning led to recovery of the wild-type characteristics. These data are consistent with the idea that the cyanide-insensitive respiratory pathway does not contain haem c and that the pathway's terminal oxidase is a quinol oxidase.