title: Molecular analysis of the community structure of nitrifying bacteria in a continuous-flow bioreactor.
abstract: We herein report the diversity and relative abundance of chemolithotrophic nitrifying bacteria in a continuous-flow bioreactor using 16S-ribosomal RNA quantitative dot-blot hybridizations. About 14.9% of the total bacterial population, determined by epifluorescence microscopy in the bioreactor suspended phase, was represented by nitrifying bacteria. Of this fraction, ammonia- and nitrite-oxidizing bacteria accounted for 10% and 90%, respectively, the latter group being mostly Nitrospira-like. On the other hand, the nitrifiers adhesion/colonization capacity on polyethylene surfaces as evaluated by scanning electron microscopy and hybridizations analyses was 12.6% of the total bacterial community adhered. Finally, in spite of the relatively small contribution of nitrifiers to the total bacterial abundance in the bioreactor, we determined a mean ammonia removal rate of 170.48 +/- 8.29 mg N l(-1) d(-1); thus, the low percentage of ammonia-oxidizing bacteria, was not limiting the bioreactor performance.
authors.affiliation: Departamento de Microbiologá, Casilla 160-C, Correo 3, Universidad de Concepción, Concepción, Chile.
authors.forename: H A
authors.initials: HA
authors.lastname: Levipan
authors.forename: E
authors.initials: E
authors.lastname: Aspé
authors.forename: H
authors.initials: H
authors.lastname: Urrutia
mesh_terms: D000641:Ammonia / Q000032:analysis; D001419:Bacteria / Q000235:genetics* / Q000648:ultrastructure; D019149:Bioreactors; D015169:Colony Count, Microbial; D004587:Electrophoresis, Agar Gel; D005798:Genes, Bacterial; D014644:Genetic Variation; D008855:Microscopy, Electron, Scanning; D009573:Nitrites / Q000032:analysis; D009586:Nitrogen Fixation / Q000235:genetics*; D010713:Phosphatidylcholines; D020959:Polyethylene; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics
chemical_list: D009573:Nitrites; D010713:Phosphatidylcholines; D012336:RNA, Ribosomal, 16S; C081346:1-(hexylthio)-2-(hexanoylamino)-1,2-dideoxy-sn-glycero-3-phosphocholine; D000641:Ammonia; D020959:Polyethylene