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J. Bacteriol., 01 1995, 432-438, Vol 177, No. 2
L Cunningham and HD Williams
The branched respiratory chain of Pseudomonas aeruginosa contains at least
two terminal oxidases which are active under normal physiological
conditions. One of these, cytochrome co, is a cytochrome c oxidase which is
completely inhibited by concentrations of the respiratory inhibitor
potassium cyanide as low as 100 microM. The second oxidase, the
cyanide-insensitive oxidase, is resistant to cyanide concentrations in
excess of 1 mM as well as to sodium azide. In this work, we describe the
isolation and characterization of a mutant of P. aeruginosa defective in
cyanide-insensitive respiration. This insertion mutant was isolated with
mini-D171 (a replication-defective derivative of the P. aeruginosa phage
D3112) as a mutagen and by screening the resulting tetracycline-resistant
transductants for the loss of ability to grow in the presence of 1 mM
sodium azide. Polarographic studies on the NADH- mediated respiration rate
of the mutant indicated an approximate 50% loss of activity, and titration
of this activity against increasing cyanide concentrations gave a
monophasic curve clearly showing the complete loss of cyanide-insensitive
respiration. The mutated gene for a mutant affected in the
cyanide-insensitive, oxidase-terminated respiratory pathway has been
designated cio. We have complemented the azide-sensitive phenotype of this
mutant with a wild-type copy of the gene by in vivo cloning with another
mini-D element, mini-D386, carried on plasmid pADD386. The complemented cio
mutant regained the ability to grow on medium containing 1 mM azide,
titration of its NADH oxidase activity with cyanide gave a biphasic curve
similar to that of the wild- type organism, and the respiration rate
returned to normal levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Isolation and characterization of mutants defective in the cyanide- insensitive respiratory pathway of Pseudomonas aeruginosa
Department of Biology, Imperial College of Science, Technology, and Medicine, London, United Kingdom.
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