We analyzed the composition and diversity of a bacterial community to determine its response to increasing salinity in the Xiangsi Lake wetland in the arid region of northwest China. We studied 12 sites, ranging from freshwater to saltwater habitats, using polymerase chain reaction (PCR)-based terminal restriction fragment length polymorphism (T-RFLP) and sequencing of the 16S rRNA genes of 5 selected samples. Cluster analysis and phylogenetic analysis revealed that the bacterial community changed significantly in response to increased salinity within the small-scale wetland (50.8 km(2)). Detailed analysis showed that (i) Betaproteobacteria can maintain balanced growth over a salinity range (from 0.34 to 6.86 g/L) through intergenus changes in community structure, followed by a sharp decrease in relative abundance (from 62.2% to 16.0%) when salinity reaches 26.18 g/L; (ii) salt-sensitive and halophobic taxa were progressively replaced by halotolerant and halophilic taxa with increasing salinity; (iii) bacterial diversity was lowest at intermediate salinity levels (6.86 g/L); and (iv) an increasing percentage of unclassified bacterial taxa were found with increasing salinity. This study has implications to improve understanding of bacterial community response to water salinization.