Affiliation:
1. School of Biosciences
2. School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, United Kingdom
Abstract
ABSTRACT
Although
Neisseria gonorrhoeae
is a prolific source of eight
c
-type cytochromes, little is known about how its electron transfer pathways to oxygen are organized. In this study, the roles in the respiratory chain to oxygen of cytochromes
c
2
,
c
4
, and
c
5
, encoded by the genes
cccA
,
cycA
, and
cycB
, respectively, have been investigated. Single mutations in genes for either cytochrome
c
4
or
c
5
resulted in an increased sensitivity to growth inhibition by excess oxygen and small decreases in the respiratory capacity of the parent, which were complemented by the chromosomal integration of an ectopic, isopropyl-β-
d
-thiogalactopyranoside (IPTG)-inducible copy of the
cycA
or
cycB
gene. In contrast, a
cccA
mutant reduced oxygen slightly more rapidly than the parent, suggesting that
cccA
is expressed but cytochrome
c
2
is not involved in electron transfer to cytochrome oxidase. The deletion of
cccA
increased the sensitivity of the
cycB
mutant to excess oxygen but decreased the sensitivity of the
cycA
mutant. Despite many attempts, a double mutant defective in both cytochromes
c
4
and
c
5
could not be isolated. However, a strain with the ectopically encoded, IPTG-inducible
cycB
gene with deletions in both
cycA
and
cycB
was constructed: the growth and survival of this strain were dependent upon the addition of IPTG, so gonococcal survival is dependent upon the synthesis of either cytochrome
c
4
or
c
5
. These results define the gonococcal electron transfer chain to oxygen in which cytochromes
c
4
and
c
5
, but not cytochrome
c
2
, provide alternative pathways for electron transfer from the cytochrome
bc
1
complex to the terminal oxidase cytochrome
cbb
3
.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
19 articles.
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