Selective enrichment and molecular characterization of a previously uncultured Nitrospira-like bacterium from activated sludge
Previously uncultured nitrite-oxidizing bacteria affiliated to the genus Nitrospira have for the first time been successfully enriched from activated sludge from a municipal wastewater treatment plant. During the enrichment procedure, the abundance of the Nitrospira-like bacteria increased to approximately 86% of the total bacterial population. This high degree of purification was achieved by a novel enrichment protocol, which exploits physiological features of Nitrospira-like bacteria and includes the selective repression of coexisting Nitrobacter cells and heterotrophic contaminants by application of ampicillin in a final concentration of 50 µg ml−1. The enrichment process was monitored by electron microscopy, fluorescence in situ hybridization (FISH) with rRNA-targeted probes and fatty acid profiling. Phylogenetic analysis of 16S rRNA gene sequences revealed that the enriched bacteria represent a novel Nitrospira species closely related to uncultured Nitrospira-like bacteria previously found in wastewater treatment plants and nitrifying bioreactors. The enriched strain is provisionally classified as ‘Candidatus Nitrospira defluvii’.
Document Type: Research Article
Affiliations: 1: Universität Hamburg, Biozentrum Klein Flottbek, Mikrobiologie, Ohnhorststr. 18, D-22609 Hamburg, Germany. 2: Department für Mikrobielle Ökologie, Universität Wien, Althanstr. 14, A-1090 Vienna, Austria. 3: Universität Osnabrück, Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, 49069 Osnabrück, Germany.
Publication date: 01 March 2006