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In this study, soil samples from the typical rice-wheat cropping system in Jiangsu Province, China, subjected to different fertilizer application treatments-no carbon (CK), urea (UR), straw (SR), pig manure (PM), starch (ST), and glucose (GL)-were used to determine potential anaerobic ammonium oxidation (anammox) rate and its association with bacterial abundance, diversity, and activity by using DNA stable isotope probing combined with N isotope tracing and molecular techniques. The effects of different organic carbon sources on anammox were significant, in the following order: GL > ST, SR > UR > PM; anammox activity differed significantly across treatments; however, the C active anammox bacteria were only closely related to Ca. Brocadia. The anammox hydrazine synthase β subunit functional gene sequences were highly associated with the Candidatus genus Brocadia in PM and CK treatments. The different organic carbon sources had different inhibitory effects with anammox rate, which dropped from 3.19 to 1.04 nmol dinitrogen gas g dry soil h among treatments. About 4.2-22.3% of dinitrogen gas emissions were attributed to anammox and indicated that a specific population of anammox bacteria was present and varied with the addition of exogenous organic compounds in paddy soils, although a small part of dinitrogen gas was emitted from the soil via anammox. [ABSTRACT FROM AUTHOR]

Electric field was applied to enhance the activity of anaerobic ammonium oxidation (anammox) bacteria for nitrogen removal in this study. The effect of different distributive modes with the total electric field time of 6 h/24 h (R2) and 18 h/24 h (R3) at 2 V/cm was determined through long-term tests. With the continuous application time increasing from 3 to 9 h in R3 (1 to 3 h in R2), the total nitrogen removal rate (NRR) showed an acceleration trend. When the electric field was applied continuously for 9 h (R3, mode 3, application-rest time: 9 h-3 h), the NRR dramatically increased 38.7 % over that of control on day 160. Besides, it was demonstrated that the increase of crude enzyme activities and the cell quantities were the main reasons for the enhancement of nitrogen removal performance of the anammox process. Additionally, transmission electron microscope observation proved the morphological change of anammox biomass under electric field application. [ABSTRACT FROM AUTHOR]