title: Enrichment, phylogenetic analysis and detection of a bacterium that performs enhanced biological phosphate removal in activated sludge.
abstract: Activated sludge communities which performed enhanced biological phosphate removal (EBPR) were phylogenetically analyzed by 16S rRNA-targeted molecular methods. Two anaerobic-aerobic sequencing batch reactors were operated with two different carbon sources (acetate vs. a complex mixture) for three years and showed anaerobic-aerobic cycles of polyhydroxybutyrate- (PHB) and phosphate-accumulation characteristic for EBPR-systems. In situ hybridization showed that the reactor fed with the acetate medium was dominated by bacteria phylogenetically related to the Rhodocyclus-group within the beta-Proteobacteria (81% of DAPI-stained cells). The reactor with the complex medium was also predominated by this phylogenetic group albeit at a lesser extent (23% of DAPI-stained cells). More detailed taxonomic information on the dominant bacteria in the acetate-reactor was obtained by constructing clone libraries of 16S rDNA fragments. Two different types of Rhodocyclus-like clones (R1 and R6) were retrieved. Type-specific in situ hybridization and direct rRNA-sequencing revealed that R6 was the type of the dominant bacteria. Staining of intracellular polyphosphate- and PHB-granules confirmed that the R6-type bacterium accumulates PHB and polyphosphate just as predicted by the metabolic models for EBPR. High similarities to 16S rDNA fragments from other EBPR-sludges suggest that R6-type organisms were present and may play an important role in EBPR in general. Although the R6-type bacterium is closely related to the genus Rhodocyclus, it did not grow phototrophically. Therefore, we propose a provisional new genus and species Candidatus Accumulibacter phosphatis.
authors.affiliation: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Dübendorf, Switzerland.
authors.forename: R P
authors.initials: RP
authors.lastname: Hesselmann
authors.forename: C
authors.initials: C
authors.lastname: Werlen
authors.forename: D
authors.initials: D
authors.lastname: Hahn
authors.forename: J R
authors.initials: JR
authors.lastname: van der Meer
authors.forename: A J
authors.initials: AJ
authors.lastname: Zehnder
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001483:Base Sequence; D001673:Biodegradation, Environmental; D004269:DNA, Bacterial / Q000032:analysis; D004275:DNA, Ribosomal / Q000032:analysis; D006885:Hydroxybutyrates / Q000378:metabolism; D017403:In Situ Hybridization; D007211:Indoles; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010710:Phosphates / Q000378:metabolism*; D010802:Phylogeny; D012329:RNA, Bacterial / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012722:Sewage / Q000382:microbiology*; D013194:Staining and Labeling
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D006885:Hydroxybutyrates; D007211:Indoles; D010710:Phosphates; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012722:Sewage; C007293:DAPI