Ecophysiology of Defluviicoccus-related tetrad-forming organisms in an anaerobic-aerobic activated sludge process

Man Tak Wong, Wen Tso Liu

Research output: Contribution to journalArticlepeer-review


A group of uncultured tetrad-forming organisms (TFOs) was enriched in an acetate-fed anaerobic-aerobic sequencing membrane bioreactor showing deteriorated enhanced biological phosphorus removal capacity. Based on 16S rRNA gene clone library and fluorescence in situ hybridization (FISH) analyses, these TFOs were identified as novel members of the Defluviicoccus cluster in the Alphaproteobacteria, accounting for 90 ± 5% of the EUBmix FISH-detectable bacterial cell area in the reactor biomass. Microautoradiography in combination with FISH and polyhydroxyalkanoate (PHA) staining revealed that these Defluviicoccus-related TFOs could take up and transform acetate, lactate, propionate and pyruvate, but not aspartic acid and glucose, into PHA under anaerobic conditions. In contrast, under continuous anaerobic-aerobic cultivation, Defluviicoccus vanus, the only cultured strain from the cluster, was able to take up glucose with concurrent glycogen consumption and PHA production under anaerobic conditions. Under subsequent aerobic conditions, the accumulated PHA was utilized and the biomass glycogen levels were restored. These findings not only re-confirmed these Defluviicoccus-related TFOs as glycogen-accumulating organisms, but also revealed unexpected levels of physiological, phylogenetic and morphological diversity among members of the Defluviicoccus cluster.

Original languageEnglish (US)
Pages (from-to)1485-1496
Number of pages12
JournalEnvironmental Microbiology
Issue number6
StatePublished - Jun 2007
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Ecology, Evolution, Behavior and Systematics


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