Abundance and community structure of ammonium monooxygenase (amoA) genes in the wet season of liaohe estuary sediments

Abstract

Ammonia oxidation is an important part of the global nitrogen cycle. Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are important players in the ammoxidation process. In this study, 13 sediment samples from the Liaohe estuary were collected in the wet season. The abundances of 16S rRNA and amoA genes were detected by real-time fluorescence quantitative PCR. The diversity and community structure of AOA and AOB were investigated by constructing clone libraries. The AOA and AOB amoA gene abundances ranged from 3.10 × 106–2.85 × 107 and 6.59 × 105–1.20 × 107 copies/g wet deposit, respectively. At all sites, AOA abundance was greater than AOB (AOA: AOB = 2.2–86.5). The ratio of AOA: archaeal 16S rRNA gene abundances and AOB: bacterial 16S rRNA gene abundances were 4.6 × 10−3–1.5 × 10−2 and 1.5 × 10−6–1.0 × 10−4. Phylogenetic analysis showed that the AOA amoA sequences were mainly Nitrosophaera and Nitrosopumilus, and most of the AOB amoA sequences belong to unclassified bacteria, which mainly were detected in estuarine sediments and wetland soils. AOA and AOB community had an obvious spatial heterogeneity. In addition, canonical correspondence analysis showed that the salinity, ammonia, total phosphorus, total organic carbon, sand, and silt content were the main driven factors of AOA and AOB community structure, in which the sand and silt content had a significant contribution.