Identification, Characterization, and Classification of Genes Encoding Perchlorate Reductase

Department of Microbiology, Southern Illinois University, Carbondale, IL 62901, USA.
Journal of Bacteriology (Impact Factor: 2.81). 09/2005; 187(15):5090-6. DOI: 10.1128/JB.187.15.5090-5096.2005
Source: PubMed


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 α- and β-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 α-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.

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    • "PRMs are ubiquitous and can reduce the compound under anoxic conditions, where ClO 4 − functions as terminal electron acceptor. Microbial reduction of ClO 4 − is catalized by two enzymes, perchlorate reductase (coded by pcrABCD gene) and chlorite dismutase (coded by cld gene) (Bender et al., 2004, 2005). Perchlorate reductase reduces ClO 4 − to ClO 3 − and finally to ClO 2 − , whereas, chlorite dismutase converts ClO 2 − into innocuous Cl − and O 2 . "
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    ABSTRACT: A microbial consortium reducing high level of perchlorate was developed and in a fed batch bioreactor using acetate as substrate perchlorate was reduced at 0.25g/g vss. day. Under stable performance, the microbial community structure of the reactor was analyzed through molecular and phenotypic methods. The diversity of bacteria and archaea were analyzed through whole cell Fluorescence In-Situ Hybridization (FISH) and PCR-Denaturing Gradient Gel Electrophoresis (DGGE), whereas higher trophic community was analyzed phenotypically. FISH analysis revealed the presence of alpha, beta, gamma and delta proteobacteria in the sludge, dominated by beta proteobacteria (68.7%). DGGE analysis of bacteria revealed the presence of a single known perchlorate reducing bacterium-Dechloromonas, nitrate reducers like Thaeura and Azoarcus and a number of other genera so far not reported as perchlorate or nitrate reducing. The archaea community was represented by an acetoclastic methanogen, Methanosaeta harundinacea. We have also observed the presence of an acetate consuming flagellate, Polytomella sp. in significant number in the reactor. Archaea and protozoa community in perchlorate treating bioreactor is reported first time in this study and point out further the significance of non perchlorate reducing but acetate scavenging microbial groups in acetate fed perchlorate treating reactors. Copyright © 2015 Elsevier GmbH. All rights reserved.
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    • "One example from the latter subgroup is the chlorate reductase of Ideonella dechloratans (Malmqvist et al., 1994), which was purified and characterized by Danielsson Thorell et al. (2003). From sequence comparison , the closest relatives of this enzyme in the DMSO reductase family are selenate reductase of Thauera selenatis (Schröder et al., 1997) and DMS dehydrogenase of Rhodovolum sulfidophilum (McDevitt et al., 2002), rather than the (per)chlorate reductases from Dechloromonas species investigated by Bender et al. (2005). Reduction of chlorate is a part of the ATP-generating respiratory chain operating when the bacteria are grown in the absence of oxygen. "
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    ABSTRACT: The electron donor for periplasmic chlorate reductase of Ideonella dechloratans has been suggested to be a soluble cytochrome c. We describe here the purification of the 9-kDa periplasmic cytochrome c, denoted cytochrome c-Id1, and demonstrate its ability to serve as an electron donor for purified chlorate reductase. The reaction rate was found to be linearly dependent on the cytochrome c concentration in the range of 0.6-4 μM. A route for electron transport involving a soluble cytochrome c is similar to that found for other periplasmic oxidoreductases of the dimethyl sulfoxide reductase family, but different from that suggested for the (per)chlorate reductase of Dechloromonas species.
    Full-text · Article · May 2011 · FEMS Microbiology Letters
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    • "Cell ratios were estimated from the gene copy numbers using the following assumptions: one pcrA copy and two nirS copies per cell, as carried in the genome of perchlorate-and nitrate-reducing Dechloromonas aromatica RCB (Coates et al., 2001; Bender et al., 2005); one nirK copy per copper denitrifier cell (Philippot, 2006); an average of four copies of 16S rRNA genes per bacterial cell (Klappenbach et al., 2001). "
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    ABSTRACT: The effect of nitrate, acetate, and hydrogen on native perchlorate-reducing bacteria (PRB) was examined by conducting microcosm tests using vadose soil collected from a perchlorate-contaminated site. The rate of perchlorate reduction was enhanced by hydrogen amendment and inhibited by acetate amendment, compared with unamendment. Nitrate was reduced before perchlorate in all amendments. In hydrogen-amended and unamended soils, nitrate delayed perchlorate reduction, suggesting that the PRB preferentially use nitrate as an electron acceptor. In contrast, nitrate eliminated the inhibitory effect of acetate amendment on perchlorate reduction and increased the rate and the extent, possibly because the preceding nitrate reduction/denitrification decreased the acetate concentration that was inhibitory to the native PRB. In hydrogen-amended and unamended soils, perchlorate reductase gene (pcrA) copies, representing PRB densities, increased with either perchlorate or nitrate reduction, suggesting that either perchlorate or nitrate stimulates the growth of the PRB. In contrast, in acetate-amended soil pcrA increased only when perchlorate was depleted: a large portion of the PRB may have not utilized nitrate in this amendment. Nitrate addition did not alter the distribution of the dominant pcrA clones in hydrogen-amended soil, likely because of the functional redundancy of PRB as nitrate-reducers/denitrifiers, whereas acetate selected different pcrA clones from those with hydrogen amendment.
    Full-text · Article · May 2011 · FEMS Microbiology Ecology
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