Denitrification is a biological process whereby nitrate (NO₃-) is reduced to nitrogen gas (N₂) via three intermediates: nitrite (NO₂-), nitric oxide (NO) and nitrous oxide (N₂O), the latter of which is an important greenhouse gas. Denitrification enzymes catalyze each of these biochemical transformations. The purpose of this research was to determine the gene expression dynamics of Pseudomonas mandelii PD30 in liquid medium in the presence or absence of nitrate using RT-qPCR. Quantification was performed using primers targeting the cnorB gene, which encodes the nitric oxide reductase enzyme. Pseudomonas mandelii is a dominant cultivable denitrifier isolated from potato fields. P. mandelii cells were grown as pure cultures in Tryptic Soy Broth over 24 h in the presence or absence of 0.1% NO₃ under anaerobic conditions. Cells were harvested, their RNA extracted and then subjected to qRT-PCR to assay for denitrification gene expression. The concentrations of NO₃- and NO₂- in the liquid media and N₂O in the headspace were measured over time. P.mandelii cells in both treatments demonstrated similar patterns of cnorB gene induction during the first three hours of growth. Preliminary results indicated a 33-fold induction in cnorB gene expression in NO₃-treated cells, and a 7-fold induction under no-nitrate conditions at the 3-h time-point. Subsequently, cells treated with nitrate maintained a constant level of approximately log 8 cnorB gene transcripts per microgram RNA, whereas cells from the no-nitrate treatment demonstrated a decrease in cnorB gene expression beyond the 3-hour time-point almost to basal levels of log 6 transcripts per microgram RNA. Accumulations of headspace N₂O were detected at 3 h and continued to increase over the 24-h period in cells grown with nitrate, whereas no-nitrate controls did not accumulate any nitrous oxide. Nitrate levels remained non-limiting for the first six hours of the experiment.