Nitric oxide reductase gene expression and nitrous oxide production in nitrate-grown Pseudomonas mandelii.
Pure cultures of Pseudomonas mandelii were incubated with or without nitrate, which acts as a substrate and an electron acceptor for denitrification. Nitric oxide reductase (cnorB) gene expression was measured using a quantitative reverse transcription-PCR, and nitrous oxide emissions were measured by gas chromatography. P. mandelii cells in either the presence or absence of nitrate demonstrated an increase in cnorB gene expression during the first 3 h of growth. The level of expression of cnorB in nitrate-amended cells remained high (average, 2.06 x 10(8) transcripts/microg of RNA), while in untreated cells it decreased to an average of 3.63 x 10(6) transcripts/microg of RNA from 4 to 6 h. Nitrous oxide accumulation in the headspace was detected at 2 h, and cumulative emissions continued to increase over a 24-h period to 101 mumol in nitrate-amended cells. P. mandelii cnorB gene expression was not detected under aerobic conditions. These results demonstrate that P. mandelii cnorB gene expression was induced 203-fold at 4 h when nitrate was present in the medium. Accumulations of N(2)O indicated that the cNorB enzyme was synthesized and active.
Saleh-Lakha
Saleema
S
Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, New Brunswick, Canada E3B 4Z7.
Shannon
Kelly E
KE
Goyer
Claudia
C
Trevors
Jack T
JT
Zebarth
Bernie J
BJ
Burton
David L
DL
D000332:Aerobiosis; D002849:Chromatography, Gas; D020869:Gene Expression Profiling; D009566:Nitrates / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000096:biosynthesis* / Q000235:genetics; D011549:Pseudomonas / Q000201:enzymology* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D009566:Nitrates; D010088:Oxidoreductases; C034747:nitric-oxide reductase; D009609:Nitrous Oxide