The aim of this study was to characterize bacterial communities in vertical flow constructed wetlands (VFCWs) using Illumina high-throughput sequencing. The bacterial communities developed lower richness and diversity in response to clogging. Bacterial diversity did not overtly decrease with depth. A variety of bacterial phyla were found in VFCWs' bacterial communities, including Bacteroidetes, Actinobacteria and Acidobacteria, among which Proteobacteria was dominant. At the genus level, a spatiotemporal variation was illustrated in the diversity and structure of bacterial communities. Clustering analysis of bacterial composition in the operational taxonomic units (OTUs) at the phylum and genus levels had a consistent trend, namely, that bacterial communities were more similar at similar column depths. (C) 2017 Elsevier Ltd. All rights reserved.