Abundance and Diversity of Aerobic/Anaerobic Ammonia/Ammonium-Oxidizing Microorganisms in an Ammonium-Rich Aquitard in the Pearl River Delta of South China.

Natural occurring groundwater with abnormally high ammonium concentrations was discovered in the aquifer-aquitard system in the Pearl River Delta, South China. The community composition and abundance of aerobic/anaerobic ammonia/ammonium-oxidizing microorganisms (AOM) in the aquitard were investigated in this study. The alpha subunit of ammonia monooxygenase gene (amoA) was used as the biomarker for the detection of aerobic ammonia-oxidizing archaea (AOA) and bacteria (AOB), and also partial 16S rRNA gene for Plantomycetes and anaerobic ammonium-oxidizing (anammox) bacteria. Phylogenetic analysis showed that AOA in this aquitard were affiliated with those from water columns and wastewater treatment plants; and AOB were dominated by sequences among the Nitrosomonas marina/Nitrosomonas oligotropha lineage, which were affiliated with environmental sequences from coastal eutrophic bay and subtropical estuary. The richness and diversity of both AOA and AOB communities had very little variations with the depth. Candidatus Scalindua-related sequences dominated the anammox bacterial community. AOB amoA gene abundances were always higher than those of AOA at different depths in this aquitard. The Pearson moment correlation analysis showed that AOA amoA gene abundance positively correlated with pH and ammonium concentration, whereas AOB amoA gene abundance negatively correlated with C/N ratio. This is the first report that highlights the presence with low diversity of AOM communities in natural aquitard of rich ammonium.

Distribution patterns of ammonia-oxidizing bacteria and anammox bacteria in the freshwater marsh of Honghe wetland in Northeast China.

Community characteristics of aerobic ammonia-oxidizing bacteria (AOB) and anaerobic ammonium-oxidizing (anammox) bacteria in Honghe freshwater marsh, a Ramsar-designated wetland in Northeast China, were analyzed in this study. Samples were collected from surface and low layers of sediments in the Experimental, Buffer, and Core Zones in the reserve. Community structures of AOB were investigated using both 16S rRNA and amoA (encoding for the α-subunit of the ammonia monooxygenase) genes. Majority of both 16S rRNA and amoA gene-PCR amplified sequences obtained from the samples in the three zones affiliated with Nitrosospira, which agreed with other wetland studies. A relatively high richness of ß-AOB amoA gene detected in the freshwater marsh might suggest minimal external pressure was experienced, providing a suitable habitat for ß-AOB communities. Anammox bacteria communities were assessed using both 16S rRNA and hzo (encoding for hydrazine oxidoreductase) genes. However, PCR amplification of the hzo gene in all samples failed, suggesting that the utilization of hzo biomarker for detecting anammox bacteria in freshwater marsh might have serious limitations. Results with 16S rRNA gene showed that Candidatus Kuenenia was detected in only the Experimental Zone, whereas Ca. Scalindua including different lineages was observed in both the Buffer and Experimental Zones but not the Core Zone. These results indicated that both AOB and anammox bacteria have specific distribution patterns in the ecosystem corresponding to the extent of anthropogenic impact.

Niche specificity of ammonia-oxidizing archaeal and bacterial communities in a freshwater wetland receiving municipal wastewater in Daqing, Northeast China.

Ecophysiological differences between ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) enable them to adapt to different niches in complex freshwater wetland ecosystems. The community characters of AOA and AOB in the different niches in a freshwater wetland receiving municipal wastewater, as well as the physicochemical parameters of sediment/soil samples, were investigated in this study. AOA community structures varied and separated from each other among four different niches. Wetland vegetation including aquatic macrophytes and terrestrial plants affected the AOA community composition but less for AOB, whereas sediment depths might contribute to the AOB community shift. The diversity of AOA communities was higher than that of AOB across all four niches. Archaeal and bacterial amoA genes (encoding for the alpha-subunit of ammonia monooxygenases) were most diverse in the dry-land niche, indicating O2 availability might favor ammonia oxidation. The majority of AOA amoA sequences belonged to the Soil/sediment Cluster B in the freshwater wetland ecosystems, while the dominant AOB amoA sequences were affiliated with Nitrosospira-like cluster. In the Nitrosospira-like cluster, AOB amoA gene sequences affiliated with the uncultured ammonia-oxidizing beta-proteobacteria constituted the largest portion (99%). Moreover, independent methods for phylogenetic tree analysis supported high parsimony bootstrap values. As a consequence, it is proposed that Nitrosospira-like amoA gene sequences recovered in this study represent a potentially novel cluster, grouping with the sequences from Gulf of Mexico deposited in the public databases.