[Study progress on the mechanism of heterotrophic nitrification]

Nitrification plays an important role in the nitrogen cycle. Autotrophic bacteria have traditionally been regarded as the nitrifying agents. However, research in last few decades has established that a lot of heterotrophic microorganisms also make contribution to nitrification. Heterotrophic nitrification has become an issue for scientific research and environment management. In this overview, both the location of heterotrophic microorganisms and the methods of detection and isolation which take the polyphyletic nature of heterotrophic bacteria into account are briefly presented. The study on the mechanism which focuses on the enzymes, functional genes, electron transfer and metabolism pathway of heterotrophic nitrification are mainly reviewed. In the end, the problems lying in the research of the mechanism of the heterotrophic nitrification are proposed and future research directions are suggested.