Environmental Variables Affecting Nitrification Rates and Distributions

Environmental Variables Affecting Nitrification Rates and Distributions 

Using the N-serve inhibition method with uptake to estimate nitrifica- 

AOB communities were detected by terminal restriction fragment analysis of amoA genes (Bernhard et al., 2005). Nitrosospira-likc sequences were also identified as the seawater dominants in this environment. 

Rysgaard et al. (1999) tested the effect of salinity on nitrification in a Danish estuary to determine whether the increased desorption of NH4+ from sediments was responsible for the decreasing nitrification rates at high salinity. They concluded that salinity influenced nitrification rates independently of NH4+ concentrations and suggested that some physiological factor must be involved. 

Both NH3 oxidizers and N02 oxidizers, but especially the former, are susceptible to inhibition by a wide range of compounds, and several different modes of action have been documented (Bedard and Knowles, 1989). The two most common modes of inhibition are (1) interference with the active site of the primary enzyme (i.e., NH3 monooxygenase in AOB N02 oxidoreductase in NOB) by compounds that share structural homology with NH3 or N02 and (2) metal binding compounds, which interfere with the action or availability of copper in the NH3-oxidizing enzymes. In both NH3- and N02 -oxidizers, the susceptibility to inhibitors by key enzymes forms the basis of some methods used to measure the rate of nitrification in the environment (see above). 

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Environmental Variables Affecting Nitrification Rates and Distributions 234... 

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