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Applied and Environmental Microbiology, August 2007, p. 5118-5124, Vol. 73, No. 16
0099-2240/07/$08.00+0 doi:10.1128/AEM.00503-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
,
M. Isabel Igeño, and
Rafael Blasco
Departamento de Bioquímica, Biología Molecular y Genética, Facultad de Veterinaria, Universidad de Extremadura, Cáceres, Spain
Received 5 March 2007/ Accepted 8 June 2007
Pseudomonas pseudoalcaligenes CECT5344 grows in minimal medium containing cyanide as the sole nitrogen source. Under these conditions, an O2-dependent respiration highly resistant to cyanide was detected in cell extracts. The structural genes for the cyanide-resistant terminal oxidase, cioA and cioB, are clustered and encode the integral membrane proteins that correspond to subunits I and II of classical cytochrome bd, although the presence of heme d in the membrane could not be detected by difference spectra. The cio operon from P. pseudoalcaligenes presents a singular organization, starting upstream of cioAB by the coding sequence of a putative ferredoxin-dependent sulfite or nitrite reductase and spanning downstream two additional open reading frames that encode uncharacterized gene products. PCR amplifications of RNA (reverse transcription-PCR) indicated the cyanide-dependent up-regulation and cotranscription along the operon. The targeted disruption of cioA eliminates both the expression of the cyanide-stimulated respiratory activity and the growth with cyanide as the nitrogen source, which suggests a critical role of this cytochrome bd-related oxidase in the metabolism of cyanide by P. pseudoalcaligenes CECT5344.
Published ahead of print on 15 June 2007.
Supplemental material for this article may be found at http://aem.asm.org/.
Present address: Centro de Investigaciones Biológicas, CSIC, Spain.
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