Molecular Existence and Diversity of Nitrite-Dependent Anaerobic Methane Oxidizing (n-Damo) Bacteria in the Lakes of Badain of the Gobi Desert

Abstract

Nitrite-dependent anaerobic methane oxidation (n-damo) process, mediated by Candidatus Methylomirabilis oxyfera of the candidate phylum NC10, was discovered recently which plays an important role in coupling the global nitrogen and carbon cycles. However, the distribution and diversity of this new anaerobic methane-oxidizing microorganism have not been investigated in desert lakes yet. The present study successfully retrieved n-damo bacterial 16S rRNA and pmoA gene sequences using PCR technique from lakes in Badain Jaran Desert of China. Phylogenetic analyses showed that n-damo bacteria widely occurred in brine and freshwater lakes on the desert with high diversity, including both sediment and water samples. The results of quantitative PCR indicated that the abundance of the 16S rRNA gene in lake sediments varied from 1.12 ± 0.68 × 105 to 1.64 ± 0.70 × 105 copies g−1 (dry weight), while that in water samples per milliliter was generally one order of magnitude lower than sediments. Correlation analyses suggested that n-damo bacterial abundance and diversity strongly depended on salinity. In lake sediments, the distribution, abundance, and diversity of n-damo bacteria were significantly associated with depth due to the concentration gradient of the NOx- and ammonium. This study provided new insights into both the n-damo community patterns and its interaction with ambient environmental factors in the desert lake ecosystem.