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Journal of Bacteriology, August 2005, p. 5090-5096, Vol. 187, No. 15
0021-9193/05/$08.00+0 doi:10.1128/JB.187.15.5090-5096.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Ching Shang,2
Romy Chakraborty,2
Sara M. Belchik,1
John D. Coates,2 and
Laurie A. Achenbach1*
Department of Microbiology, Southern Illinois University, Carbondale, Illinois 62901,1 Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 945982
Received 3 March 2005/ Accepted 25 April 2005
The reduction of perchlorate to chlorite, the first enzymatic step in the bacterial reduction of perchlorate, is catalyzed by perchlorate reductase. The genes encoding perchlorate reductase (pcrABCD) in two Dechloromonas species were characterized. Sequence analysis of the pcrAB gene products revealed similarity to
- and ß-subunits of microbial nitrate reductase, selenate reductase, dimethyl sulfide dehydrogenase, ethylbenzene dehydrogenase, and chlorate reductase, all of which are type II members of the microbial dimethyl sulfoxide (DMSO) reductase family. The pcrC gene product was similar to a c-type cytochrome, while the pcrD gene product exhibited similarity to molybdenum chaperone proteins of the DMSO reductase family members mentioned above. Expression analysis of the pcrA gene from Dechloromonas agitata indicated that transcription occurred only under anaerobic (per)chlorate-reducing conditions. The presence of oxygen completely inhibited pcrA expression regardless of the presence of perchlorate, chlorate, or nitrate. Deletion of the pcrA gene in Dechloromonas aromatica abolished growth in both perchlorate and chlorate but not growth in nitrate, indicating that the pcrABCD genes play a functional role in perchlorate reduction separate from nitrate reduction. Phylogenetic analysis of PcrA and other
-subunits of the DMSO reductase family indicated that perchlorate reductase forms a monophyletic group separate from chlorate reductase of Ideonella dechloratans. The separation of perchlorate reductase as an activity distinct from chlorate reductase was further supported by DNA hybridization analysis of (per)chlorate- and chlorate-reducing strains using the pcrA gene as a probe.
Present address: Department of Biochemistry, University of Missouri-Columbia, Columbia, MO 65211.
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