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J Bacteriol, June 1998, p. 3197-3204, Vol. 180, No. 12
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Transcriptional Regulation of Alcaligenes eutrophus Hydrogenase Genes

Edward Schwartz,* Ulrike Gerischer,dagger and Bärbel Friedrich

Institut für Biologie der Humboldt-Universität zu Berlin and Institut für Pflanzenphysiologie und Mikrobiologie der Freien Universität Berlin, Berlin, Germany

Received 21 January 1998/Accepted 8 April 1998

Alcaligenes eutrophus H16 produces a soluble hydrogenase (SH) and a membrane-bound hydrogenase (MBH) which catalyze the oxidation of H2, supplying the organism with energy for autotrophic growth. The promoters of the structural genes for the SH and the MBH, PSH and PMBH, respectively, were identified by means of the primer extension technique. Both promoters were active in vivo under hydrogenase-derepressing conditions but directed only low levels of transcription under conditions which repressed hydrogenase synthesis. The cellular pools of SH and MBH transcripts under the different growth conditions correlated with the activities of the respective promoters. Also, an immediate and drastic increase in transcript pool levels occurred upon derepression of the hydrogenase system. Both promoters were dependent on the minor sigma factor sigma 54 and on the hydrogenase regulator HoxA in vivo. PSH was stronger than PMBH under both heterotrophic and autotrophic growth conditions. The two promoters were induced at approximately the same rates upon derepression of the hydrogenase system in diauxic cultures. The response regulator HoxA mediated low-level activation of PSH and PMBH in a heterologous system.

* Corresponding author. Mailing address: Institut für Biologie, Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestr. 117, D-10115 Berlin, Germany. Phone: 49-30-2093-8117. Fax: 49-30-2093-8102. E-mail: edward=schwartz{at}biologie.hu-berlin.de.

dagger Present address: Abteilung Angewandte Mikrobiologie, Universität Ulm, D-89069 Ulm, Germany.

J Bacteriol, June 1998, p. 3197-3204, Vol. 180, No. 12
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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