title: Improved isolation strategies allowed the phenotypic differentiation of two Nitrospira strains from widespread phylogenetic lineages.
abstract: The second step of nitrification, the oxidation of nitrite to nitrate, is vital for the functioning of the nitrogen cycle, but our understanding of the ecological roles of the involved microorganisms is still limited. The known diversity of Nitrospira, the most widely distributed nitrite-oxidizing bacteria, has increased remarkably by analyses of 16S rRNA and functional gene sequences. However, only few representatives could be brought into laboratory cultures so far. In this study, two Nitrospira from activated sludge were isolated using novel approaches together with established methods. Highly enriched 'Candidatus Nitrospira defluvii' was separated from concomitant heterotrophs by taking advantage of its resistance against ampicillin and acriflavine. Beside this member of lineage I, a novel species of lineage II, named N. lenta, was initially enriched at 10°C and finally purified by using optical tweezers. The tolerance to elevated nitrite levels was much higher in N. defluvii than in the more fastidious N. lenta and was accompanied by pronounced biofilm formation. Phylogenetic classification of 12 additional enrichments indicated that Nitrospira lineage I is common in extreme and moderate ecosystems like lineage II. The new cultures will help to explore physiological and genomic differences affecting niche separation between members of this highly diverse genus.
authors.affiliation: Biocenter Klein Flottbek, Department of Microbiology and Biotechnology, University of Hamburg, Ohnhorststr. 18, D-22609 Hamburg, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Nowka
authors.affiliation: Biocenter Klein Flottbek, Department of Microbiology and Biotechnology, University of Hamburg, Ohnhorststr. 18, D-22609 Hamburg, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Off
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Althanstr. 14, A-1090 Vienna, Austria.
authors.forename: Holger
authors.initials: H
authors.lastname: Daims
authors.affiliation: Biocenter Klein Flottbek, Department of Microbiology and Biotechnology, University of Hamburg, Ohnhorststr. 18, D-22609 Hamburg, Germany eva.spieck@uni-hamburg.de.
authors.forename: Eva
authors.initials: E
authors.lastname: Spieck
mesh_terms: D000167:Acriflavine / Q000494:pharmacology; D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001419:Bacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D018441:Biofilms / Q000254:growth & development*; D024901:Drug Resistance, Multiple, Bacterial; D017753:Ecosystem; D009566:Nitrates / Q000378:metabolism; D058465:Nitrification; D009573:Nitrites / Q000378:metabolism; D052898:Optical Tweezers; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D009566:Nitrates; D009573:Nitrites; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D000167:Acriflavine; D000667:Ampicillin
keywords: Nitrospira; diversity; isolation; nitrification; nitrite-oxidizing bacteria; physiology; wastewater