Analysis of microbial community structure in MBR with different ammonia concentrations using fluorescence in situ hybridization

The intrinsic relationship between the microbial community structure and nitrification was investigated in the membrane bioreactor (MBR) with different influent NH4+-N concentrations. Fluorescence in situ hybridization (FISH) was adopted for analyzing microbial community structure. Proteobacteria, Actinobacteria, Cytophaga-flexibacter-bacteroides, Chloroflexi, Nitrobacter sp. and Ammonia-oxidizing bacteria were detected. The results show that when the influent NH4+-N concentrations are 35, 3.47 and 100 mg/L, Proteobacteria accounts for 51%, 44% and 39% of total bacteria, while the sum of Ammonia-oxidizing and Nitrobacter sp. accounts for 28%, 4% and 43%, respectively. Abundant filamentous Betaproteobacteria is detected in MBR with lower NH4+-N concentration. Actinobacteria and Chloroflexi are also found to be increased simultaneously. Ammonia-oxidizing bacteria and Nitrobacter sp. are enriched and dominant in MBR with higher NH4+-N load. Correlation analysis indicates that Ammonia-oxidizing bacteria and Nitrobacter sp. are positively correlated with NH4+-N removal.