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Journal of Bacteriology, March 2001, p. 1780-1783, Vol. 183, No. 5
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.5.1780-1783.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Role for draTG and rnf Genes in Reduction of 2,4-Dinitrophenol by Rhodobacter capsulatus

Lara P. Sáez,1 Patricia García,1 Manuel Martínez-Luque,1 Werner Klipp,2 Rafael Blasco,1,* and Francisco Castillo1

Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, 14071 Córdoba, Spain,1 and Lehrstuhl für Biologie der Mikroorganismen, Fakultät für Biologie, Universität Bochum, D-44780 Bochum, Germany2

Received 28 July 2000/Accepted 2 December 2000

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.

* Corresponding author. Mailing address: Departamento de Bioquímica y Biología Molecular, Edificio C6, 1a Planta, Campus de Rabanales, Universidad de Córdoba, 14071 Córdoba, Spain. Phone: 34 957218318. Fax: 34 957218592. E-mail: bb1blplr{at}uco.es.

Journal of Bacteriology, March 2001, p. 1780-1783, Vol. 183, No. 5
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.5.1780-1783.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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