Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Denitrification is an alternative type of anaerobic respiration in which nitrate is reduced to gaseous products via nitrite. The key step in this process is the reduction of nitrite to nitric oxide, which is catalyzed by two structurally different but functionally equivalent forms of nitrite reductase encoded by the nirK and nirS genes. Cultivation-independent studies based on these functional marker genes showed that in the environment there was a dominance of organisms with nirK and nirS genes presumably derived from organisms that have not been cultured yet. However, the phylogenetic affiliation of these organisms has not been resolved since the ability to denitrify is widespread in phylogenetically unrelated organisms. To unravel the phylogeny of the organisms from which the nitrite reductase (nirK) genes originated, one option is to use a special variant of whole-cell hybridization termed recognition of individual genes-fluorescence in situ hybridization (RING-FISH). In RING-FISH a multiply labeled transcript polynucleotide probe is used to detect a single gene on the bacterial chromosome during FISH. Here, RING-FISH was used with laboratory cultures and environmental samples, such as activated sludge. Furthermore, probe-based cell sorting using magnetic beads could also be carried out with mixtures of pure cultures, which led to effective depletion of the nirK-negative organism but capture of the nirK-positive organism, which was demonstrated by terminal restriction fragment length polymorphism analysis based on 16S rRNA genes. The results indicate that RING-FISH coupled with probe-based cell sorting could be used with environmental samples, which could provide a means for phylogenetic classification of nirK-type denitrifiers. Thus, the results of RING-FISH could increase our understanding of the phylogeny and function of denitrifying microorganisms in the environment.
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PMID:Application of recognition of individual genes-fluorescence in situ hybridization (RING-FISH) to detect nitrite reductase genes (nirK) of denitrifiers in pure cultures and environmental samples. 1907 10

Enhanced biological phosphorus removal (EBPR) is a widely applied method for nutrients removal, although little is known about the key genes regulating the complex biochemical transformations occurring in activated sludge during phosphorus removal. In the present study, the nitrite reductase gene (nirS) diversity and the denitrifying polyphosphate accumulating organisms (DPAOs) population, grown in a bench scale, two-sludge, continuous flow plant, operating for biological anoxic phosphorus removal (DEPHANOX-type), fed with municipal wastewater, were examined by means of physicochemical analyses and the application of molecular techniques. The DEPHANOX configuration highly influenced biomass phosphorus as well as polyhydroxyalkanoates content and facilitated the enrichment of the DPAOs population. The application of double probe fluorescent in situ hybridization (double probe FISH) technique revealed that DPAOs comprised 20% of the total bacterial population. Based on clone libraries construction and nirS gene sequencing analysis, a pronounced shift in denitrifying bacteria diversity was identified during activated sludge acclimatization. Moreover, nirS gene sequences distinct from those detected in any known bacterial strain or environmental clone were identified. This is the first report studying the microbial properties of activated sludge in a DEPHANOX-type system using molecular techniques.
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PMID:Denitrifying polyphosphate accumulating organisms population and nitrite reductase gene diversity shift in a DEPHANOX-type activated sludge system fed with municipal wastewater. 2105 3

Sequential mRNA fluorescence in situ hybridization (mRNA FISH) and fluorescence-assisted cell sorting (SmRFF) was used for the identification of nitrite-reducing bacteria in mixed microbial communities. An oligonucleotide probe labeled with horseradish peroxidase (HRP) was used to target mRNA of nirS, the gene that encodes nitrite reductase, the enzyme responsible for the dissimilatory reduction of nitrite to nitric oxide. Clones for nirS expression were constructed and used to provide proof of concept for the SmRFF method. In addition, cells from pure cultures of Pseudomonas stutzeri and denitrifying activated sludge were hybridized with the HRP probe, and tyramide signal amplification was performed, conferring a strongly fluorescent signal to cells containing nirS mRNA. Flow cytometry-assisted cell sorting was used to detect and physically separate two subgroups from a mixed microbial community: non-fluorescent cells and an enrichment of fluorescent, nitrite-reducing cells. Denaturing gradient gel electrophoresis (DGGE) and subsequent sequencing of 16S ribosomal RNA (rRNA) genes were used to compare the fragments amplified from the two sorted subgroups. Sequences from bands isolated from DGGE profiles suggested that the dominant, active nitrite reducers were closely related to Acidovorax BSB421. Furthermore, following mRNA FISH detection of nitrite-reducing bacteria, 16S rRNA FISH was used to detect ammonia-oxidizing and nitrite-oxidizing bacteria on the same activated sludge sample. We believe that the molecular approach described can be useful as a tool to help address the longstanding challenge of linking function to identity in natural and engineered habitats.
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PMID:Identification of nitrite-reducing bacteria using sequential mRNA fluorescence in situ hybridization and fluorescence-assisted cell sorting. 2237 Aug 76