[Community structure of microbes involved in nitrification and denitrification in typical shrimp-farming water]

We analyzed the community and diversity of microorganisms involved in nitrification and denitrification of nitrogen cycle in typical aquaculture water in order to manage microbiological degradation of NH4+ and NO2-, to control nitrogen pollution and nitrogen cycle in shrimp-farming water.

Samples were analyzed by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) graph. We constructed clone libraries of the typical sample based on the functional gene ammonia monooxygenase gene (amoA), nitrite oxidoreductase gene (nxrA), and nitrite reductase gene (nirS). These three libraries were analyzed by using Restriction Fragment Length Polymorphism (RFLP).

Phylogenetic analysis showed that all sequences from amoA library were clustered into beta-Proteobacteria, including Nitrosomonas (81%) and Nitrosospira (19%). Clones from nxrA library were clustered into alpha-Proteobacteria and delta-Proteobacteria, including Nitrobacter (92%) and Desulfobacteraceae (8%). Clones from nirS library were clustered into alpha-Proteobacteria, beta-Proteobacteria and Actinobacteria. Beta-Proteobacteria was the dominant group that consisted of Azoarcus (25%), Brachymonas (5%), and Thauera (20%). In alpha-Proteobacteria group, Sophophora (10%), Polymorphum (25%), Ruegeria (5%) were detected. In the Actinobacteria group, Streptomyces (10%) was detected.

Microorganisms involved in nitrification and denitrification of nitrogen cycle were abundant. In the aquaculture water, Nitrosomonas was the main performer of ammoxidation, Nitrobacter was the main performer of nitrification, and many kinds of populations played important roles in the denitrification.