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Influence of copper on expression of nirS, noRrB and nosZ and the transcription and activity of NIR, NOR and N₂O in the denitrifying soil bacteria Pseudomonas stutzeri

Black, Amanda
Hsu, PCL
Hamonts, KE
Clough, Timothy
Condron, LM
Journal Article
Fields of Research
ANZSRC::3106 Industrial biotechnology , ANZSRC::3107 Microbiology
Reduction of the potent greenhouse gas nitrous oxide (N₂O) occurs in soil environments by the action of denitrifying bacteria possessing nitrous oxide reductase (N₂OR), a dimeric copper (Cu)-dependent enzyme producing environmentally benign dinitrogen (N₂). We examined the effects of increasing Cu concentrations on the transcription and activity of nitrite reductase (NIR), nitric oxide reductase (NOR) and N₂OR in Pseudomonas stutzeri grown anaerobically in solution over a 10-day period. Gas samples were taken on a daily basis and after 6 days, bacterial RNA was recovered to determine the expression of nirS, norB and nosZ encoding NIR, NOR and N₂OR respectively. Results revealed that 0.05 mM Cu caused maximum conversion of N₂O to N₂ via bacterial reduction of N₂O. As soluble Cu generally makes up less than 0.001% of total soil Cu, extrapolation of 0.05 mg l-l soluble Cu would require soils to have a total concentration of Cu in the range of, 150-200 μg g-1 to maximize the proportion of N₂O reduced to N₂. Given that many intensively farmed agricultural soils are deficient in Cu in terms of plant nutrition, providing a sufficient concentration of biologically accessible Cu could provide a potentially useful microbial-based strategy of reducing agricultural N₂O emissions.
(C) 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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