To better understand the effect of salinity on denitrification communities,soils along a salinity gradient (ranging from 7.32 to 1.70 mS cm 1) in a wetland along the Yellow Sea coastline in Jiangsu Province,China,were studied using both culture-dependent and-independent methods.Culture efforts yielded 82 isolates in total,81.7% of which were close relatives of Bacillus sp.based on partial sequences of their 16S rRNA genes.Denaturing gradient gel electrophoresis (DGGE) analysis based on 16S rRNA sequences suggested possible existence of bacterial community succession along the salinity gradient.Clone library analysis based on nosZ gene sequences (coding nitrous oxide reductase) showed that operational taxonomic units (OTUs) associated with α-proteobacteria dominated in all three soils,whereas those associated with β-and γ-subdivisions showed a clear succession.In the high salinity soil,only the OTUs associated with α-subdivision were found.In the medium salinity soil,small proportions of β-(6.5%) and γ-associated (19.6%) OTUs were found.In the low salinity soil,the proportions were further increased to 33% and 25% for β-and γ-Proteobacteria,respectively.Statistic analysis using Unifrac P test showed that nosZ-communities in different saline soils were significantly different from each other.It could be concluded that α-subdivision of nosZ-community tended to be sustained in high salinity environments whereas β-and γ-subdivisions,especially the former,tended to be sustained in low salinity environments.Salinity was the key determinant of nosZ-community composition in the environment.
