title: Impact of copper on the diversity, abundance and transcription of nitrite and nitrous oxide reductase genes in an urban European estuary.
abstract: In this study, the effects of increasing copper (Cu) concentrations on the denitrification pathway and on the diversity of a denitrifier community and gene expression were evaluated in intertidal sandy sediments of the Douro River estuary (north-west Portugal). The results demonstrated that sediment denitrification rates were highly affected by Cu; almost complete inhibition (85%) of the process was observed in sediments amended with 60 μg Cu g(-1) wet wt sediment. Moreover, the addition of Cu stimulated the accumulation of both N(2)O and NO(2)(-) and inhibited the rate of NO(3)(-) uptake. Further, the amendment with even the lowest Cu concentration (4 μg Cu g(-1) wet wt sediment) yielded a drastic decrease in the abundance of nirK, nirS and nosZ (between 79% and 81%) assessed by means of real-time PCR. In agreement, reverse transcription-PCR-denaturing gradient gel electrophoresis analysis of nirK, nirS and nosZ transcripts showed a progressive decrease in the diversity of the transcription products of these genes with an increase of the Cu concentration.
authors.affiliation: Centre of Marine and Environmental Research (CIIMAR), University of Porto, Porto, Portugal. cmag@icbas.up.pt
authors.forename: Catarina M
authors.initials: CM
authors.lastname: Magalhães
authors.forename: Ana
authors.initials: A
authors.lastname: Machado
authors.forename: Patrícia
authors.initials: P
authors.lastname: Matos
authors.forename: Adriano A
authors.initials: AA
authors.lastname: Bordalo
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D016000:Cluster Analysis; D003300:Copper / Q000737:chemistry*; D004269:DNA, Bacterial / Q000235:genetics; D058645:Denaturing Gradient Gel Electrophoresis; D058440:Denitrification; D019015:Geologic Sediments / Q000737:chemistry; D009566:Nitrates / Q000032:analysis / Q000378:metabolism; D009569:Nitric Oxide / Q000032:analysis / Q000378:metabolism; D009573:Nitrites / Q000032:analysis / Q000378:metabolism*; D009609:Nitrous Oxide / Q000032:analysis / Q000378:metabolism; D010088:Oxidoreductases / Q000032:analysis / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011174:Portugal; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D045483:Rivers / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D004269:DNA, Bacterial; D009566:Nitrates; D009573:Nitrites; D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D009569:Nitric Oxide; D003300:Copper; D010088:Oxidoreductases; C022763:nitrous oxide reductase; D009609:Nitrous Oxide