Microbial community analysis of enhanced biological phosphorus removal process and identification of polyphosphate accumulating organisms by molecular approach

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Fundamental research about enhanced biological phosphorus removal (EBPR) process is now making great progress because of the new microbial community analysis methods such as molecular techniques. This research was carried to reveal the relationship between microbial community and function of EBPR sludge using 16S-rDNA approach.In this research, at first, laboratory scale reactors were operated using acetate, glutamate, propionate, glucose or peptone as a main carbon source respectively. The expression of phosphorus removal activity was monitored by batch experiments and the microbial community change was monitored by Denaturing gradient gel electrophoresis (DGGE) using 16S-rDNA fragments. By comparing phosphorus removal activity and microbial community change, polyphosphate accumulating organisms were screened. In addition, by sequencing the whole length of 16S-rDNA of target bacteria by using cloning method and developing gene probes which can specifically detect the target bacteria and combining with the polyphosphate staining method and fluorescent in situ hybridization, capability of accumulating polyphosphate by screened bacteria was investigated.As a result, it was demonstratedd that gram-positive bacteria with high GC content accumulated polyphosphate in the reactor fed with mainly peptone and this gram positive bacteria was considered as the second putative polyphosphate accumulating organisms (PAOs) after Rhodocyclus related bacteria, which has been already considered as PAOs candidates. In addition, as another bacteria which accumulated polyphosphate but was not Rhodocyclus related bacteria nor gram positive bacteria was detected, it was clearly shown that still unknown PAOs should exist. In this way, it was shown that the EBPR is achieved by the combination of several PAOs