Kristiansen, Rikke2; Nguyen, Hien Thi Thu3; Saunders, Aaron Marc3; Nielsen, Jeppe Lund3; Wimmer, Reinhard3; Le, Vang5; McIlroy, Simon Jon3; Petrovski, Steve6; Seviour, Robert J.6; Calteau, Alexandra7; Nielsen, Kåre Lehmann3; Nielsen, Per Halkjær1
1 Department of Chemistry and Bioscience, The Faculty of Engineering and Science, Aalborg University, VBN2 EcoDesign, The Faculty of Engineering and Science, Aalborg University, VBN3 Section of Biotechnology, The Faculty of Engineering and Science, Aalborg University, VBN4 The Faculty of Engineering and Science, Aalborg University, VBN5 The Faculty of Medicine, Aalborg University, VBN6 La Trobe Univ, Biotechnol Res Ctr7 CEA/DSV/IG, Genoscope and CNRS-UMR 8030, Laboratoire d’Analyse Bioinformatique en Ge´nomique et Me´tabolisme, Evry
Members of the genus Tetrasphaera are considered to be putative polyphosphate accumulating organisms (PAOs) in enhanced biological phosphorus removal (EBPR) from wastewater. Although abundant in Danish full-scale wastewater EBPR plants, how similar their ecophysiology is to ‘Candidatus Accumulibacter phosphatis’ is unclear, although they may occupy different ecological niches in EBPR communities. The genomes of four Tetrasphaera isolates (T. australiensis, T. japonica, T. elongata and T. jenkinsii) were sequenced and annotated, and the data used to construct metabolic models. These models incorporate central aspects of carbon and phosphorus metabolism critical to understanding their behavior under the alternating anaerobic/aerobic conditions encountered in EBPR systems. Key features of these metabolic pathways were investigated in pure cultures, although poor growth limited their analyses to T. japonica and T. elongata. Based on the models, we propose that under anaerobic conditions the Tetrasphaerarelated PAOs take up glucose and ferment this to succinate and other components. They also synthesize glycogen as a storage polymer, using energy generated from the degradation of stored polyphosphate and substrate fermentation. During the aerobic phase, the stored glycogen is catabolized to provide energy for growth and to replenish the intracellular polyphosphate reserves needed for subsequent anaerobic metabolism. They are also able to denitrify. This physiology is markedly different to that displayed by ‘Candidatus Accumulibacter phosphatis’, and reveals Tetrasphaera populations to be unusual and physiologically versatile PAOs carrying out denitrification, fermentation and polyphosphate accumulation.