Affiliation:
1. Lehrstuhl für Mikrobiologie, Technische Universität München, 85350 Freising, Germany,1 and
2. Department of Environmental Engineering, Aalborg University, DK-9000 Aalborg, Denmark2
Abstract
ABSTRACT
Uncultivated
Nitrospira
-like bacteria in different biofilm and activated-sludge samples were investigated by cultivation-independent molecular approaches. Initially, the phylogenetic affiliation of
Nitrospira
-like bacteria in a nitrifying biofilm was determined by 16S rRNA gene sequence analysis. Subsequently, a phylogenetic consensus tree of the
Nitrospira
phylum including all publicly available sequences was constructed. This analysis revealed that the genus
Nitrospira
consists of at least four distinct sublineages. Based on these data, two 16S rRNA-directed oligonucleotide probes specific for the phylum and genus
Nitrospira
, respectively, were developed and evaluated for suitability for fluorescence in situ hybridization (FISH). The probes were used to investigate the in situ architecture of cell aggregates of
Nitrospira
-like nitrite oxidizers in wastewater treatment plants by FISH, confocal laser scanning microscopy, and computer-aided three-dimensional visualization. Cavities and a network of cell-free channels inside the
Nitrospira
microcolonies were detected that were water permeable, as demonstrated by fluorescein staining. The uptake of different carbon sources by
Nitrospira
-like bacteria within their natural habitat under different incubation conditions was studied by combined FISH and microautoradiography. Under aerobic conditions, the
Nitrospira
-like bacteria in bioreactor samples took up inorganic carbon (as HCO
3
−
or as CO
2
) and pyruvate but not acetate, butyrate, and propionate, suggesting that these bacteria can grow mixotrophically in the presence of pyruvate. In contrast, no uptake by the
Nitrospira
-like bacteria of any of the carbon sources tested was observed under anoxic or anaerobic conditions.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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