ABSTRACT
Nitrite oxidoreductase(NXR) is the key enzyme responsible for the oxidation of NO2-to NO3-in nitrite-oxidizing bacteria.Since NXR is a dissoluble enzyme,located at the inner side of the membranes of cells,its function is dependent on the electron transfer chain related to membranes.This paper reviews the advances in study on NXR,including the structure,catalysis mechanism and the impact of different factors.New techniques applied in recent studies and research prospects are also presented.
ABSTRACT
One factor at a time design and first order exponential model were applied to investigate the effects of the four major factors(temperature,ionic strength,pH and osmo-regulator) in the preservation process of nitrite oxidization bacteria(NOB),and a first order decay kinetics was introduced.The result showed that the anoxic decay rate of nitrifying bacteria reduced from 0.25 to 0.015,the half life was extend to 53d at 4℃,pH7.60,ionic strength 0.035mol/kg.The protecting effect of glycerin showed obviously better than that of other cryoprotectants at 4℃.
ABSTRACT
Terminal restriction fragment length polymorphism (T_RFLP) analysis is a culture- independent approach for analyzing microbial community in environment. It bases on PCR technology, and its process includes DNA extraction of environmental samples, amplification of genes encoding the 16S rRNA, 18S rRNA or enzymes with fluorescently labeled primers, the restriction enzyme digestion of PCR products, cap- illary electrophoresis and the analysis of T_RFLP profile. It has been proved to be powerful applied on mi- crobial community in environment since developed in 1997. Currently, T_RFLP rarely applied in China, and it has no applications on microbial community analysis of nitrifying bacteria. In this article, the fundamental principle of this technique and the recent applications of T_RFLP on microbial community are summarized; in addition, it illustrates the confinements of conventional culture-dependent of nitrifying bacteria and the foreground of T_RFLP applying on microbial community structure analysis of nitrifying bacteria.