Article: article from journal or magazin.
Enrichment, phylogenetic analysis and detection of a bacterium that performs enhanced biological phosphate removal in activated sludge.
Systematic and Applied Microbiology
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.
Aerobiosis, Anaerobiosis, Bacteria/classification, Bacteria/genetics, Base Sequence, Biodegradation, Environmental, DNA, Bacterial/analysis, DNA, Ribosomal/analysis, Hydroxybutyrates/metabolism, In Situ Hybridization, Indoles, Microscopy, Fluorescence, Molecular Sequence Data, Nucleic Acid Hybridization, Phosphates/metabolism, Phylogeny, RNA, Bacterial/analysis, RNA, Ribosomal, 16S/analysis, Sewage/microbiology, Staining and Labeling
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