Beer, M.J.Kong, Y.Seviour, R.2025-12-172025-12-172004Microbiology (United Kingdom), 2004; 150(7):2267-22751350-08721465-2080https://hdl.handle.net/1959.8/88924<jats:p> Activated sludge plants designed to remove phosphorus microbiologically often perform unreliably. One suggestion is that the polyphosphate-accumulating organisms (PAO) are out-competed for substrates by another group of bacteria, the glycogen-accumulating organisms (GAO) in the anaerobic zones of these processes. This study used fluorescence <jats:italic>in situ</jats:italic> hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) to analyse the communities from laboratory-scale anaerobic : aerobic sequencing batch reactors. Members of the genus <jats:italic>Sphingomonas</jats:italic> in the <jats:italic>α</jats:italic> - <jats:italic>Proteobacteria</jats:italic> were present in large numbers in communities with poor phosphorus removal capacity where the biomass had a high glycogen content. Their ability to store poly- <jats:italic>β</jats:italic> -hydroxyalkanoates anaerobically, but not aerobically, and not accumulate polyphosphate aerobically is consistent with these organisms behaving as GAO there. No evidence was found to support an important role for the <jats:italic>γ</jats:italic> - <jats:italic>Proteobacteria</jats:italic> as possible GAO in these communities, although these bacterial populations have been considered in other studies to act as possible competitors for the PAO. </jats:p>enCopyright status unknownJournal article10.1099/mic.0.26825-0