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Candidatus Halomonas phosphatis’, a novel polyphosphate-accumulating organism in full-scale enhanced biological phosphorus removal plants

Authors

  • Hien Thi Thu Nguyen,

    1. Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark.
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  • Jeppe Lund Nielsen,

    1. Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark.
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  • Per Halkjær Nielsen

    Corresponding author
    1. Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark.
      E-mail phn@bio.aau.dk; Tel. (+45) 9940 8503; Fax (+45) 9814 1808.
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E-mail phn@bio.aau.dk; Tel. (+45) 9940 8503; Fax (+45) 9814 1808.

Summary

Microautoradiography combined with fluorescence in situ hybridization (MAR-FISH) was used to screen for potential polyphosphate-accumulating organisms (PAOs) in full-scale enhanced biological phosphorus removal (EBPR) plants. Clone library analyses and application of MAR-FISH using newly designed probes revealed that small rods related to uncultured Halomonas within the gammaproteobacterial family Halomonadaceae were actively involved in uptake of orthophosphate. Although deeply branched in the Gammaproteobacteria, they were not targeted by the gammaproteobacterial probe (GAM42a). A part of them were also not targeted with the general bacterial probes (EUBmix). They could take up short-chain fatty acids (e.g. acetate and propionate) and ethanol under both anaerobic and aerobic conditions. Polyhydroxyalkanoate storage was observed under anaerobic conditions. There was no indication of a denitrifying capability. A survey of the occurrence of these Halomonas-PAOs in 23 full-scale EBPR plants revealed that they made up 0.5–5.7% of all bacteria in the plants, and were often in higher abundance than the well-described PAOs ‘Candidatus Accumulibacter phosphatis’. This indicates a potentially important role for these uncultured Halomonas bacteria in the EBPR process in full-scale plants and we propose to name them ‘Candidatus Halomonas phosphatis’.

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