Two dissimilatory microbial pathways are responsible for nitrate reduction: Denitrification and Dissimilatory Nitrate Reduction to Ammonium (DNRA, or nitrate ammonification). Denitirification is an anaerobic respiratory process where nitrate and/or nitrite serve as electron acceptors and are converted to gaseous products like N₂O and/or N₂via several intermediates. This process is favored at high nitrate concentrations and a low C/N ratio relative to DNRA. DNRA is a competing process for nitrate reduction performed by nitrate ammonifiers and is favored at low nitrate concentrations and a high C/N ratio. Contrasting kinetics for electron acceptor usage for denitrifiers and nitrate ammonifiers might help to explain their competitiveness for nitrate and nitrite. The objective of this study is to determine apparent kinetic parameters for nitrate and nitrite with intact cells of denitrifiers, nitrate ammonifiers and bacteria capable of both processes.