Occurrence And Distribution Of Nitrate/Nitrite‐dependent Anaerobic Methane Oxidation(n‐damo) In Water‐level Fluctuation Zone Of The Three Gorges Reservoir

Nitrate/nitrite-dependent anaerobic methane oxidation(n-damo), mediated by “Candidatus Methylomirabilis oxyfera”(M. oxyfera), was discovered in 2006. And the discoveries of such organisms supplements biologicalchemical carbon and nitrogen cycle.To date, the researches for n-damo were mainly concentrated in different habitats and sewage treatment reactor, however the occurrence of this progress in the Three Gorges Reservoir is still unclear. In the present study, the occurrence and biogeographic distribution of n-damo bacteria in water-level fluctuation zone of the Three Gorges Reservoir were investigated using quantitative PCR assays, 16 S r RNA and particulate methane monooxygenase gene clone library analyses and physicochemical analyses. The results are as follows:(1) In the current study, the results of q PCR indicated that M. oxyfera-like bacteria were presented throughout examined samples, and gene clone library technology successfully amplified specific genes of n-damo bacteria in the Three Gorges Reservoir. Results showed above confirmed the occurrence of n-damo bacteria in the Three Gorges Reservoir.(2) Different clusters of n-damo bacteria related to M. oxyfera were detected in the selected water-level fluctuation zone simultaneously. The Group a were all observed in sediment samples below the water, and n-damo bacteria belongs to Group b were dominant in both investigated area.(3) Abundance of n-damo bacteria in different elevation were examined with values of 102~105 copies g-1 dry soil. Higher abundance of n-damo bacteria in sediment samples(abundance of n-damo in sediment and soil samples collected at natural water-level fluctuation in 2013.10 varied from 1.05×103~1.45×103 copies g-1 dry soil and 4.79×102~5.16×102 copies g-1 dry soil respectively and 2014.4 was 4.21×104~5.32×104copies g-1dry soid and 3.17×103~7.69×103 copies g-1 dry soil, abundance of n-damo in sediment and soil samples collected at natural water-level fluctuation in 2013.10 varied from 2.01×103~3.54×103copies g-1 dry soil and 8.98×102~1.09×102 copies g-1 dry soil) indicated that sediment, which were below the water, were the dominant distribution area for n-damo bacteria. Additionally, Pearson’s correlation analysis showed that abundance of n-damo bacteria in natural water-level fluctuation zone were not affected by environmental factors, while OM was the dominant variable determined the abundance of n-damo in anthropogenic influenced zone.