Community structure and spatial distribution of anaerobic ammonium oxidation bacteria in the sediments of Chongming eastern tidal flat in summer

The objectives of this study were to identify whether there were Anaerobic Ammonium Oxidation(ANAMMOX) bacteria in the surface sediments of Chongming eastern tidal flat in the Yangtze estuary and the feature of their community structure and spatial distribution. Based on the total DNA extracted from the surface sediments of Chongming eastern tidal flat, ANAMMOX-specific 16S rDNA fragments were amplified. PCR products were cloned and sequenced, and an ANAMMOX-specific 16S rDNA gene library was established. Phylogenetic tree was constructed using MEGA5 after the sequences were checked in the GenBank database. Phylogenetic analysis indicated that the clone sequences CM-L-7 and CM-L-18 had 98% identities with ANAMMOX bacteria Candidatus 'Scalindua sp.'. CM-L-13 had 94% identities with Candidatus 'Scalindua wagneri'. CM-M-6 had 94% identities with Candidatus 'Kuenenia sp.'. CM-M-22 had 95% identities with Anaerobic ammonium-oxidizing planctomycete JMK-1.CM-H-15 had 94% identities with Candidatus 'Kuenenia stuttgartiensis'. The results indicated that there were ANAMMOX bacteria in the surface sediments of Chongming eastern tidal flat, but the ANAMMOX species were diverse in different tidal flats: Candidatus'Scalindua' was the predominant group in the low tidal flat, while Candidatus 'Kuenenia' was the major population in the high tidal flat and the middle tidal flat. In comparison with the high and low tidal flats, the community structure of ANAMMOX bacteria in the middle tidal flat was the most complicated. A portion of the sequences related to uncultivated bacteria outside the known ANAMMOX cluster, probably indicated that there were potential ANAMMOX bacteria in the sediments of Chongming eastern tidal flat.