[Comparison of microbial community structure in MBRs treating different wastewater]

In order to investigate the microbial community structures in different membrane bioreactors, total bacterial genomic DNA was extracted from biomass in four MBRs treating different wastewater. The microbial community structures were studied by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and cloning-sequencing. Furthermore, and the sequences were used for homology analysis and then two phylogenetic trees were constructed. Results indicate that each MBR owns its specific ecological community after a long-term of operation. Influent wastewater composition has a significant impact on total bacterial community structures. Population diversity, which is in the bioreactor fed with more complex components wastewater, is higher than those of other MBRs. The Shannon Index are 0.77 and 0.78. Proteobacteria and Bacillus, which contain 8 OUTs and 2 OUTs, are the climax communities in the investigable MBRs. The profiles of ammonia-oxidizing bacterial community in the four reactors are very similar. There may exist several modes of nitrification and denitrification in MBR because sequences revealed that there exist multitude nitrifying organisms, in which Nitrosomonas are the most predominant, and two denitrifying bacterium (uncultured Achromobacter sp. and uncultured denitrifying bacterium)in reactors.