This study compared the whole composition of microbial community in continuous-flow (MBR) and batch-fed (discontinuous) (MSBR) aerobic membrane bioreactors using high-density universal 16S rRNA Microarray, which includes 506,944 probes targeted to 8935 clusters in 16S rRNA gene sequences. The Microarray results shown both MBR and MSBR had high microbial diversity. 1126 and 1002 bacterial subfamilies were detected and can separate as 37 and 32 phyla in MBR and MSBR, respectively. Proteobacteria was the predominant phylum, 703 and 597 subfamilies were found in two systems, which constituted 62.4% and 59.6% of the whole bacteria. Gammaproteobacteria and Alphaproteobacteria were the dominant classes in Proteobacteria. It occupied 38.1% and 26.3%, 31.2% and 39.2% for MBR and MSBR, respectively. Bacteroidetes, Firmicutes and Acidobacteria were the subdominant groups, occupying around 9.4% and 7.6%, 6.1% and 6.5%, 6.0% and 9.0% of the total bacteria in two reactors. Some bacteria groups such as Actinobacteria, Chloroflexi, Cyanobacteria, Verrucomicrobia, Spirochaetes and Unclassified phylum also found more than 15 subfamilies. All the results shown the MBR system had more bacteria community diversity than MSBR's. Moreover, it was very interested that MBR and MSBR had almost the same bacterial composition except Enterobacteriaceae. 63 OTUs belong to Enterobacteriaceae were detected in MBR, while just 10 OTUs were found in MSBR. That's maybe one of the reasons leading to the difference of the bacterial diversity between two bioreactors.
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