title: Isolation and characterization of 3-nitrophenol-degrading bacteria associated with rhizosphere of Spirodela polyrrhiza.
abstract: BACKGROUND
  The accelerated biodegradation of 3-nitrophenol (3-NP) in the rhizosphere of giant duckweed (Spirodela polyrrhiza) was investigated.
  
  
  METHODS
  Biodegradation of 3-nitrophenol in the rhizosphere of a floating aquatic plant, S. polyrrhiza, was investigated by using three river water samples supplemented with 10 mg l(-1) of 3-NP. Isolation and enrichment culture of 3-NP-degrading bacteria were performed in basal salts medium containing 3-NP (50 mg l(-1)). The isolated strains were physiologically and phylogenetically characterized by using an API20NE kit and 16S rRNA gene sequencing.
  
  
  CONCLUSIONS
  Accelerated removal of 3-NP (100%) was observed in river water samples with S. polyrrhiza compared with their removal in plant-free river water. Also, 3-NP persisted in an autoclaved solution with aseptic plants, suggesting that the accelerated 3-NP removal resulted largely from degradation by bacteria inhabiting the plant rather than from adsorption and uptake by the plant. We successfully isolated six and four strains of 3-NP-degrading bacteria from the roots of S. polyrrhiza and plant-free river water, respectively. Phylogenetic analysis based on 16S rRNA gene divided the 3-NP-degrading bacteria into two taxonomic groups: the genera Pseudomonas and Cupriavidus. The strains belonging to the genus Cupriavidus were only isolated from the roots of duckweed. All strains isolated from the roots utilized 3-NP (0.5 mM) as a sole carbon and energy source, indicating that they could have contributed to the accelerated degradation of 3-NP in the rhizosphere of S. polyrrhiza.
  
  
  CONCLUSIONS
  The rhizoremediation using S. polyrrhiza and its rhizosphere bacteria can be an effective strategy for cleaning up the 3-NP-contaminated surface waters.
authors.affiliation: Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Kofu, Yamanashi, Japan.
authors.forename: Risky Ayu
authors.initials: RA
authors.lastname: Kristanti
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kanbe
authors.forename: Tony
authors.initials: T
authors.lastname: Hadibarata
authors.forename: Tadashi
authors.initials: T
authors.lastname: Toyama
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Mori
mesh_terms: D029064:Araceae / Q000382:microbiology*; D001673:Biodegradation, Environmental; D049921:Cupriavidus / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005618:Fresh Water; D008969:Molecular Sequence Data; D009596:Nitrophenols / Q000378:metabolism* / Q000493:pharmacokinetics; D010802:Phylogeny; D011549:Pseudomonas / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S; D058441:Rhizosphere; D045483:Rivers
chemical_list: D009596:Nitrophenols; D012336:RNA, Ribosomal, 16S; C049017:3-nitrophenol