Affiliation:
1. Departamento de Bioquı́mica y Biologı́a Molecular, Universidad de Córdoba, 14071 Córdoba, Spain,1 and
2. Lehrstuhl für Biologie der Mikroorganismen, Fakultät für Biologie, Universität Bochum, D-44780 Bochum, Germany2
Abstract
ABSTRACT
The phototrophic bacterium
Rhodobacter capsulatus
is able to reduce 2,4-dinitrophenol (DNP) to 2-amino-4-nitrophenol enzymatically and thus can grow in the presence of this uncoupler. DNP reduction was switched off by glutamine or ammonium, but this short-term regulation did not take place in a
draTG
deletion mutant. Nevertheless, the target of DraTG does not seem to be the nitrophenol reductase itself since the ammonium shock did not inactivate the enzyme. In addition to this short-term regulation, ammonium or glutamine repressed the DNP reduction system. Mutants of
R. capsulatus
affected in
ntrC
or
rpoN
exhibited a 10-fold decrease in nitroreductase activity in vitro but almost no DNP activity in vivo. In addition, mutants affected in
rnfA
or
rnfC
, which are also under NtrC control and encode components involved in electron transfer to nitrogenase, were unable to metabolize DNP. These results indicate that NtrC regulates dinitrophenol reduction in
R. capsulatus
, either directly or indirectly, by controlling expression of the Rnf proteins. Therefore, the Rnf complex seems to supply electrons for both nitrogen fixation and DNP reduction.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
13 articles.
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