Another possible disadvantage of applying N[H.sub.4.sup.+] fertilisers is that NH4 can accumulate due to lack of autotrophic nitrifier
bacterial activity and high concentrations of N[H.sub.4.sup.+] can be phytotoxic (Meecham and Bell 1977b).
The research findings were that "the overall contribution of periphytic biofilm to net denitrification was less than that of the sediment but greater than that of the water column." The study laid stress how one should incorporate bacterial denitrifier and nitrifier
genes and periphytic biofilm characteristics during model construction to make an preciser prediction of denitrification in a shallow and stagnant water-sediment system.
Oenema, 2001: Role of nitrifier
denitrification in the production of nitrous oxide.
and denitrifier molecular operational taxonomic unit compositions from sites of a freshwater estuary of Chesapeake Bay.
Bothe, "Physiological and molecular biological characterization of ammonia oxidation of the heterotrophic nitrifier
Pseudomonas putida " Current Microbiology, vol.
Further studies on the nitrifier
bacterial composition are required.
Ammonia oxidation pathways and nitrifier
denitrification are significant sources of N2O and NO under low oxygen availability.
In complex soil environments, ammonia oxidation and nitrifier
denitrification generally coexist with heterotrophic denitrification (Hu et al.
Although several strains belong to P putida are reported as heterotrophic nitrifier
 or aerobic denitrifier , they are all mesophilic bacteria.
Some other research showed that the increase in nitrifier
activity, over time, in brass pipes occurred only after levels of copper leaching to water dropped below about 0.1 ppm as the pipe metal aged (Zhang et al.
A comparison of NO and N2O production by the autotrophic nitrifier
Nitrosomonas europaea and the heterotrophic nitrifier