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Journal of Bacteriology, March 2000, p. 1390-1398, Vol. 182, No. 5
Institut für Mikrobiologie,
Martin-Luther-Universität Halle-Wittenberg, D-06099 Halle,
Germany
Received 19 July 1999/Accepted 16 November 1999
Ralstonia sp. strain CH34 is resistant to nickel and
cobalt cations. Resistance is mediated by the cnr
determinant located on plasmid pMOL28. The cnr genes are
organized in two clusters, cnrYXH and cnrCBA.
As revealed by reverse transcriptase PCR and primer extension,
transcription from these operons is initiated from promoters located
upstream of the cnrY and cnrC genes. These two
promoters exhibit conserved sequences at the
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Regulation of the cnr Cobalt and Nickel
Resistance Determinant from Ralstonia sp. Strain
CH34
10 (CCGTATA) and
35 (CRAGGGGRAG) regions. The CnrH gene product, which is required for expression of both operons, is a sigma factor belonging to
the sigma L family, whose activity seems to be governed by the
membrane-bound CnrY and CnrX gene products in response to Ni2+. Half-maximal activation from the cnrCBA
operon was determined by using appropriate lacZ gene
fusions and was shown to occur at an Ni2+ concentration of
about 50 µM.
*
Corresponding author. Mailing address: Institut
für Mikrobiologie, Martin-Luther-Universität
Halle-Wittenberg, Kurt-Mothes-Str. 3, 06099 Halle, Germany. Phone:
(49)-345-5526352. Fax: (49)-345-5527010. E-mail:
d.nies{at}mikrobiologie.uni-halle.de.
This publication is dedicated to Hans G. Schlegel, who started the
cnr work, on his 75th birthday.
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