Diversity of ammonia-oxidizing bacteria in relation to soil environment in Ebinur Lake Wetland

Ammonia oxidation is the first and rate-limiting step of nitrification and is carried out by ammonia-oxidizing bacteria (AOB). Ebinur Lake Wetland, the most representative temperate arid zone wetland ecosystem in China, is the centre of oasis and desertification of the northern slope of Tianshan conjugate. Soil samples were collected from three sites (Tamarix ramosissima, Halocnemum strobilaceum and Phragmites australis) and different soil layers (0–5, 5–15, 15–25 and 25–35 cm) in this wetland in spring, summer and autumn and were used to characterize the diversity of AOB based on the ammonia monooxygenase (amoA) gene. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and bivariate correlation analysis were used to analyse the relationship between the diversity of AOB and soil environment factors. The PCR-DGGE indicated that the diversity of AOB was high in the entire sample and the Shannon diversity index varied from 1.369 to 2.471. The phylogenetic analysis showed that the amoA fragments were grouped into Nitrosospira sp. and Nitrosomonas sp. Most amoA gene sequences fell within the Nitrosospira sp. cluster, and only a few sequences were clustered with Nitrosomonas sp., indicating that Nitrosospira sp. may be more adaptable than Nitrosomonas sp. in this area. Bivariate correlation analysis showed that the diversity of AOB was significantly correlated with soil organic matter, conductivity, total phosphorus and nitrate in the Ebinur Lake Wetland in Xinjiang