Determination of the microbial diversity of anaerobic-aerobic activated sludge by a novel molecular biological technique

Sequential anaerobic-aerobic batch reactors were maintained on acetate/peptone and two different P/total organic carbon ratios that select for microbial communities enriched for either glycogen-accumulating organisms (GAO) or polyphosphate-accumulating organism (PAG): The community profiles of the eubacterial population and gram-positive high G-C bacteria (HGC) were characterized and compared by determining the terminal restriction fragment length polymorphisms (T-RFLP) of 16S rDNA. The HhaI+RsaI digested 5' T-RFLP patterns of the eubacterial 16S rDNA amplified from the GAO-and PAO-enriched communities were made up with 12 and 14 rank-abundant fragments (i.e., ribotypes), respectively. Among these ribotypes detected in the GAG-enriched community, only seven were found in the PAO-enriched community. The HGC group could only account for no more than 6% and 17% of the eubacterial 16S rDNA amplified from the GAO-and PAO-enriched communities, respectively. Within the HGC community, at least 16 and 10 rank-abundant ribotypes were observed in the MspI digested T-RFLP patterns of GAO-and PAO-enriched communities, respectively. Among those HGC ribotypes observed in both communities, only five were in common. These indicate that the enrichment processes leading io;the establishment ol. GAO-and FAG-specific communities caused the dramatic difference and complexity in the microbial population. (C) 1998 IAWQ. Published by Elsevier Science Ltd.