The impact of copper, nitrate and carbon status on the emission of nitrous oxide by two species of bacteria with biochemically distinct denitrification pathways.
Denitrifying bacteria convert nitrate (NO(3)             (-) ) to dinitrogen (N(2) ) gas through an anaerobic respiratory process in which the potent greenhouse gas nitrous oxide (N(2) O) is a free intermediate. These bacteria can be grouped into classes that synthesize a nitrite (NO(2)             (-) ) reductase (Nir) that is solely dependent on haem-iron as a cofactor (e.g. Paracoccus denitrificans) or a Nir that is solely dependent on copper (Cu) as a cofactor (e.g. Achromobacter xylosoxidans). Regardless of which form of Nir these groups synthesize, they are both dependent on a Cu-containing nitrous oxide reductase (NosZ) for the conversion of N(2) O to N(2) . Agriculture makes a major contribution to N(2) O release and it is recognized that a number of agricultural lands are becoming Cu-limited but are N-rich because of fertilizer addition. Here we utilize continuous cultures to explore the denitrification phenotypes of P. denitrificans and A. xylosoxidans at a range of extracellular NO(3)             (-) , organic carbon and Cu concentrations. Quite distinct phenotypes are observed between the two species. Notably, P. denitrificans emits approximately 40% of NO(3)             (-)  consumed as N(2) O under NO(3)             (-) -rich Cu-deficient conditions, while under the same conditions A. xylosoxidans releases approximately 40% of the NO(3)             (-)  consumed as NO(2)             (-) . However, the denitrification phenotypes are very similar under NO(3)             (-) -limited conditions where denitrification intermediates do not accumulate significantly. The results have potential implications for understanding denitrification flux in a range of agricultural environments.
School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK.
Heather
H
Felgate
Georgios
G
Giannopoulos
Matthew J
MJ
Sullivan
Andrew J
AJ
Gates
Thomas A
TA
Clarke
Elizabeth
E
Baggs
Gary
G
Rowley
David J
DJ
Richardson
D042441:Achromobacter denitrificans / Q000235:genetics / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D003300:Copper / Q000378:metabolism*; D058440:Denitrification; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype
D009566:Nitrates; D009573:Nitrites; D002244:Carbon; D003300:Copper; D010088:Oxidoreductases; C022763:nitrous oxide reductase; D009609:Nitrous Oxide