[Distribution and role of denitrifying, nitrifying, nitrosation and ammonifying bacteria in east lake]

The most probable number (MPN) method was employed to determine the distribution and role of four nitrogen cycle bacteria, including ammonifying bacteria, denitrifying bacteria, nitrosobacteria and nitrobacteria, in East Lake, Wuhan. The results showed that the n(MPN) of nitrosobacteria in water was most in rainy season and least in dry season, while the number in common season between them. The n(MPN) of water nitrobacteria in rainy season was less than in the other two seasons. The n(MPN) of water ammonifying and denitrifying bacteria were most in common season, least in dry season. The n(MPN) of nitrosobacteria in sediment in rainy season was more than that in other seasons. The n(MPN) of sediment nitrobacteria was most in dry season while denitrifying bacteria was more in dry season than in other seasons. The n(MPN) of ammonifying bacteria had no difference among three seasons. Compared with water phase, the n(MPN) of nitrosobacteria in sediment phase was more in rainy and dry season (p < 0.01), while nitrobacteria's number was prevailing in water phase during common and rainy season while denitrifying bacteria's was prevailing only in common season(p < 0.01). The ammonifying bacteria had no difference in water and sediment. The results demonstrated that the difference in distribution of four nitrogen cycle bacteria in two phase and three season played a significant role in nitrogen removal, which promoted ammoniation, nitrification, nitrosification and denitrification in lake. The study also found that the lg[n(MPN)] of denitrifying and ammonifying bacteria in water and sediment had significant correlation with the catching gas volume(p < 0.001). Furthermore, different season had different gas volume (p < 0.01), which showed that ammoniation and denitrification could convert organic nitrogen and nitrate into gas nitrogen(NH3, N2O, N2) and also varied greatly with different season.