The potential contribution of anammox to nitrogen loss from paddy soils in Southern China
Xiao-Ru Yang, Hu Li, San-An Nie, Jian-Qiang Su, Bo-Sen Weng, Gui-Bing Zhu, Huai-Ying Yao, Jack A. Gilbert, Yong-Guan Zhu*
Anaerobic oxidation of ammonium (anammox) process has been observed in diverse terrestrial ecosystem, while the contribution of anammox to N2 production in paddy soils is not well documented. In this study, the anammox activity and the abundance and diversity of anammox bacteria were investigated to assess anammox potential from 12 typical paddy soils collected in Southern China. Anammox bacteria related to Candidatus Brocadia and Candidatus Kuenenia and two novel unidentified clusters were detected, with Candidatus Brocadia comprising 50% of the anammox population. The prevalence of the anammox were confirmed by the quantitative PCR results based on hydrazine synthase (hzsB) genes, which showed that the abundance ranged from 1.16×104 to 9.65×104 copies per gram of dry weight. The anammox rates measured by isotope pairing technique ranged from 0.27 to 5.25 nmol N per gram of soil per hour in these paddy soils, which contributed 0.6-15% to soil N2 production. It is estimated that a total loss of 2.50 ×106 Mg N per year is linked to anammox in the paddy fields in Southern China, which implied that ca. 10% of the applied ammonia fertilizers may be lost via the anammox process. Anammox activity was significantly correlated with the abundance of hzsB gene, soil nitrate concentration and C/N ratio were significantly correlated with the anammox activity. Additionally, ammonia concentration and pH were found to be significantly correlated with the anammox bacterial structure.
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Journal：Applied and Environmental Microbiology
