title: Bacterial diversity and function of aerobic granules engineered in a sequencing batch reactor for phenol degradation.
abstract: Aerobic granules are self-immobilized aggregates of microorganisms and represent a relatively new form of cell immobilization developed for biological wastewater treatment. In this study, both culture-based and culture-independent techniques were used to investigate the bacterial diversity and function in aerobic phenol- degrading granules cultivated in a sequencing batch reactor. Denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA genes demonstrated a major shift in the microbial community as the seed sludge developed into granules. Culture isolation and DGGE assays confirmed the dominance of beta-Proteobacteria and high-G+C gram-positive bacteria in the phenol-degrading aerobic granules. Of the 10 phenol-degrading bacterial strains isolated from the granules, strains PG-01, PG-02, and PG-08 possessed 16S rRNA gene sequences that matched the partial sequences of dominant bands in the DGGE fingerprint belonging to the aerobic granules. The numerical dominance of strain PG-01 was confirmed by isolation, DGGE, and in situ hybridization with a strain-specific probe, and key physiological traits possessed by PG-01 that allowed it to outcompete and dominate other microorganisms within the granules were then identified. This strain could be regarded as a functionally dominant strain and may have contributed significantly to phenol degradation in the granules. On the other hand, strain PG-08 had low specific growth rate and low phenol degradation ability but showed a high propensity to autoaggregate. By analyzing the roles played by these two isolates within the aerobic granules, a functional model of the microbial community within the aerobic granules was proposed. This model has important implications for rationalizing the engineering of ecological systems.
authors.affiliation: Environmental Engineering Research Centre, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore.
authors.forename: He-Long
authors.initials: HL
authors.lastname: Jiang
authors.forename: Joo-Hwa
authors.initials: JH
authors.lastname: Tay
authors.forename: Abdul Majid
authors.initials: AM
authors.lastname: Maszenan
authors.forename: Stephen Tiong-Lee
authors.initials: ST
authors.lastname: Tay
mesh_terms: D000332:Aerobiosis; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D001673:Biodegradation, Environmental; D019149:Bioreactors; D018914:Cells, Immobilized; D003470:Culture Media; D004275:DNA, Ribosomal / Q000032:analysis; D004586:Electrophoresis / Q000379:methods; D005818:Genetic Engineering / Q000379:methods*; D014644:Genetic Variation; D008969:Molecular Sequence Data; D019800:Phenol / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000382:microbiology; D014865:Waste Disposal, Fluid
chemical_list: D003470:Culture Media; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D019800:Phenol