title: Isolation and characterization of facultative mixotrophic ammonia-oxidizing bacteria from constructed wetlands.
abstract: Autotrophic ammonia-oxidizing bacteria (AOB) have been widely studied in constructed wetlands systems, while mixotrophic AOB have been less thoroughly examined. Heterotrophic bacteria were isolated from wastewater and rhizospheres of macrophytes of constructed wetlands, and then cultivated in a mixotrophic medium containing ammonium and acetic acid. A molecular characterization was accomplished using ITS-PCR amplification, and phylogenetic analysis based on 16S rRNA gene sequences. Results showed the presence of 35 bacteria, among 400 initially heterotrophic isolates, that were able to remove ammonia. These 35 isolates were classified into 10 genetically different groups based on ITS pattern. Then, a collection of 10 isolates were selected because of their relatively high ammonia removal efficiencies (ARE > or = 80%) and their phylogenetic diversity. In conditions of mixotrophy, these strains were shown to be able to grow (increase of optical density OD660 during incubation with assimilation of nitrogen into cellular biomass) and to oxidize ammonia (important ammonia oxidation efficiencies, AOE between 79% and 87%). Among these facultative mixotrophic AOB, four isolates were genetically related to Firmicutes (Bacillus and Exiguobacterium), three isolates were affiliated to Actinobacteria (Arthrobacter) and three other isolates were associated with Proteobacteria (Pseudomonas, Ochrobactrum and Bordetella).
authors.affiliation: Laboratory of Treatment and Water Recycling, Centre of Research and Water Technologies, Technopark of Borj-Cedria, BP 273, 8020 Soliman, Tunisia. kouso2004@yahoo.fr
authors.forename: Soulwène
authors.initials: S
authors.lastname: Kouki
authors.forename: Neila
authors.initials: N
authors.lastname: Saidi
authors.forename: Fadhel
authors.initials: F
authors.lastname: M'hiri
authors.forename: Houda
authors.initials: H
authors.lastname: Nasr
authors.forename: Hanène
authors.initials: H
authors.lastname: Cherif
authors.forename: Hadda
authors.initials: H
authors.lastname: Ouzari
authors.forename: Abdennaceur
authors.initials: A
authors.lastname: Hassen
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D001407:Bacillus; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014871:Water Microbiology; D053833:Wetlands
chemical_list: D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D000641:Ammonia