Diversity of ammonia-oxidising bacteria and archaea in seven different estuarine sediments from Poyang Lake

In the present study, we used a culture-independent method based on library construction and sequencing to analyse the genetic diversity of the ammonia monooxygenase genes (amoA) of ammonia-oxidising archaea and bacteria in seven different estuarine sediments of Poyang Lake. The total of 67 and 38 operational taxonomic units (OTUs) (similarity <95%) of archaeal (AOA) and bacterial (AOB) amoA genes were retrieved respectively. AOA had higher diversity of amoA genes than did AOB. Phylogenetic analysis showed that AOA amoA sequences were closely related to amoA sequences from Crenarchaeota, Thaumarchaeota and some other uncultured archaea. Fragments from AOB were most associated with sequences from betaproteobacteria and some other uncultured bacteria. On the basis of Kendall's correlation coefficient, there was a significant positive correlation between AOA amoA gene diversity and temperature, and the AOB diversity was positively correlated with total nitrogen and nitrate nitrogen concentration, and negatively correlated with pH in the sediments, suggesting that AOA and AOB were probably sensitive to several environmental factors. Our work could enhance our understanding of the roles of ammonia-oxidising microorganisms in these seven estuarine sediments from Poyang Lake.