title: Relative Abundance of Nitrotoga spp. in a Biofilter of a Cold-Freshwater Aquaculture Plant Appears To Be Stimulated by Slightly Acidic pH.
abstract: The functioning of recirculation aquaculture systems (RAS) is essential to maintain water quality for fish health, and one crucial process here is nitrification. The investigated RAS was connected to a rainbow trout production system and operated at an average temperature of 13°C and pH 6.8. Community analyses of the nitrifying biofilm revealed a coexistence of Nitrospira and Nitrotoga, and it is hypothesized that a slightly acidic pH in combination with lower temperatures favors the growth of the latter. Modification of the standard cultivation approach toward lower pH values of 5.7 to 6.0 resulted in the successful enrichment (99% purity) of Nitrotoga sp. strain HW29, which had a 16S rRNA sequence similarity of 99.0% to Nitrotoga arctica. Reference cultures of Nitrospira defluvii and the novel Nitrotoga sp. HW29 were used to confirm differentiation of these nitrite oxidizers in distinct ecological niches. Nitrotoga sp. HW29 revealed pH and temperature optima of 6.8 and 22°C, respectively, whereas Nitrospira defluvii displayed the highest nitrite oxidation rate at pH 7.3 and 32°C. We report here the occurrence of Nitrotoga as one of the main nitrite-oxidizing bacteria in freshwater aquaculture systems and indicate that a slightly acidic pH, in addition to temperatures below 20°C, can be applied as a selective isolation criterion for this microorganism.
authors.affiliation: Biocenter Klein Flottbek, Microbiology and Biotechnology, University of Hamburg, Hamburg, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hüpeden
authors.affiliation: Biocenter Klein Flottbek, Microbiology and Biotechnology, University of Hamburg, Hamburg, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: Wegen
authors.affiliation: Biocenter Klein Flottbek, Microbiology and Biotechnology, University of Hamburg, Hamburg, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Off
authors.affiliation: Department of Microbiology, Faculty of Science, Radboud University, Nijmegen, The Netherlands Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Lücker
authors.affiliation: Biocenter Klein Flottbek, Microbiology and Biotechnology, University of Hamburg, Hamburg, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Bedarf
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Vienna, Austria.
authors.forename: Holger
authors.initials: H
authors.lastname: Daims
authors.affiliation: State Research Centre of Agriculture and Fisheries Mecklenburg-Vorpommern, Institute of Fisheries, Rostock, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Kühn
authors.affiliation: Biocenter Klein Flottbek, Microbiology and Biotechnology, University of Hamburg, Hamburg, Germany eva.spieck@uni-hamburg.de.
authors.forename: Eva
authors.initials: E
authors.lastname: Spieck
mesh_terms: D017756:Aquaculture; D058491:Bacterial Load; D003080:Cold Temperature; D005374:Filtration; D005618:Fresh Water; D043372:Gallionellaceae / Q000254:growth & development / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D018508:Water Purification / Q000379:methods*