Relative abundances of proteobacterial membrane-bound and periplasmic nitrate reductases in selected environments.
Dissimilatory nitrate reduction is catalyzed by a membrane-bound and a periplasmic nitrate reductase. We set up a real-time PCR assay to quantify these two enzymes, using the narG and napA genes, encoding the catalytic subunits of the two types of nitrate reductases, as molecular markers. The narG and napA gene copy numbers in DNA extracted from 18 different environments showed high variations, with most numbers ranging from 2 x 10(2) to 6.8 x 10(4) copies per ng of DNA. This study provides evidence that, in soil samples, the number of proteobacteria carrying the napA gene is often as high as that of proteobacteria carrying the narG gene. The high correlation observed between narG and napA gene copy numbers in soils suggests that the ecological roles of the corresponding enzymes might be linked.
Bru
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INRA, University of Burgundy, Soil and Environmental Microbiology, CMSE, 17 rue Sully, BP 86510, 21065 Dijon Cedex, France.
Sarr
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Philippot
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D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004777:Environment; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D050901:Nitrate Reductase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D033903:Periplasmic Proteins / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology; D016133:Polymerase Chain Reaction; D020560:Proteobacteria / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D012988:Soil Microbiology
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008565:Membrane Proteins; D033903:Periplasmic Proteins; D050901:Nitrate Reductase