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Enrichment culture

About: Enrichment culture is a(n) research topic. Over the lifetime, 1069 publication(s) have been published within this topic receiving 38357 citation(s).


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Journal ArticleDOI
TL;DR: The data suggest that amoA represents a very powerful molecular tool for analyzing indigenous ammonia-oxidizing communities due to (i) its specificity, (ii) its fine-scale resolution of closely related populations, and (iii) the fact that a functional trait rather than a phylogenetic trait is detected.
Abstract: The naturally occurring genetic heterogeneity of autotrophic ammonia-oxidizing populations belonging to the beta subclass of the Proteobacteria was studied by using a newly developed PCR-based assay targeting a partial stretch of the gene which encodes the active-site polypeptide of ammonia monooxygenase (amoA). The PCR yielded a specific 491-bp fragment with all of the nitrifiers tested, but not with the homologous stretch of the particulate methane monooxygenase, a key enzyme of methane-oxidizing bacteria. The assay also specifically detected amoA in DNA extracted from various aquatic and terrestrial environments. The resulting PCR products retrieved from rice roots, activated sludge, a freshwater sample, and an enrichment culture were used for the generation of amoA gene libraries. No false positives were detected in a set of 47 randomly selected clone sequences that were analyzed further. The majority of the environmental sequences retrieved from rice roots and activated sludge grouped within the phylogenetic radiation defined by cultured strains of the genera Nitrosomonas and Nitrosospira. The comparative analysis identified members of both of these genera in activated sludge; however, only Nitrosospira-like sequences with very similar amino acid patterns were found on rice roots. Further differentiation of these molecular isolates was clearly possible on the nucleic acid level due to the accumulation of synonymous mutations, suggesting that several closely related but distinct Nitrosospira-like populations are the main colonizers of the rhizosphere of rice. Each of the amoA gene libraries obtained from the freshwater sample and the enrichment culture was dominated by a novel lineage that shared a branch with the Nitrosospira cluster but could not be assigned to any of the known pure cultures. Our data suggest that amoA represents a very powerful molecular tool for analyzing indigenous ammonia-oxidizing communities due to (i) its specificity, (ii) its fine-scale resolution of closely related populations, and (iii) the fact that a functional trait rather than a phylogenetic trait is detected.

2,301 citations

Journal ArticleDOI
TL;DR: An autotrophic, synthetic medium for the enrichment of anaerobic ammonium-oxidizing (Anammox) micro-organisms was developed and Acetylene, phosphate and oxygen were shown to be strong inhibitors of the Anammox activity.
Abstract: An autotrophic, synthetic medium for the enrichment of anaerobic ammonium-oxidizing (Anammox) micro-organisms was developed This medium contained ammonium and nitrite, as the only electron donor and electron acceptor, respectively, while carbonate was the only carbon source provided Preliminary studies showed that the presence of nitrite and the absence of organic electron donors were essential for Anammox activity The conversion rate of the enrichment culture in a fluidized bed reactor was 3 kg NH4 + m-3 d-1 when fed with 30 mM NH4 + This is equivalent to a specific anaerobic ammonium oxidation rate of 1000-1100 nmol NH4 +h-1 (mg volatile solids)-1 The maximum specific oxidation rate obtained was 1500 nmol NH4 +h-1 (mg volatile solids)-1 Per mol NH4 + oxidized, 0041mol CO2 were incorporated, resulting in a estimated growth rate of 0001 h-1 The main product of the Anammox reaction is N2, but about 10% of the N-feed is converted to NO3 - The overall nitrogen balance gave a ratio of NH4 --conversion to NO2 --conversion and NO3 --production of 1:1-31++006:022+002 During the conversion of NH4 + with NO2 -, no other intermediates or end-products such as hydroxylamine, NO and N2O could be detected Acetylene, phosphate and oxygen were shown to be strong inhibitors of the Anammox activity The dominant type of micro-organism in the enrichment culture was an irregularly shaped cell with an unusual morphology During the enrichment for Anammox micro-organisms on synthetic medium, an increase in ether lipids was observed The colour of the biomass changed from brownish to red, which was accompanied by an increase in the cytochrome content Cytochrome spectra showed a peak at 470 nm gradually increasing in intensity during enrichment

1,168 citations

Journal ArticleDOI
TL;DR: It is demonstrated that an electricity-generating microbial consortium can be enriched using a fuel cell and that the electrochemical activity is a form of anaerobic electron transfer.
Abstract: A fuel cell was used to enrich a microbial consortium generating electricity, using organic wastewater as the fuel. Within 30 days of enrichment the maximum current of 0.2 mA was generated with a resistance of 1 kΩ. Current generation was coupled to a fall in chemical oxygen demand from over 1,700 mg l−1 down to 50 mg l−1. Denaturing gradient gel electrophoresis showed a different microbial population in the enriched electrode from that in the sludge used as the inoculum. Electron microscopic observation showed a biofilm on the electrode surface and microbial clumps. Nanobacteria-like particles were present on the biofilm surface. Metabolic inhibitors and electron acceptors inhibited the current generation. 16S ribosomal RNA gene analysis showed a diverse bacterial population in the enrichment culture. These findings demonstrate that an electricity-generating microbial consortium can be enriched using a fuel cell and that the electrochemical activity is a form of anaerobic electron transfer.

437 citations

Journal ArticleDOI
TL;DR: The results indicate that the enriched subgroup of NC10 bacteria is responsible for anaerobic methane oxidation coupled to nitrite reduction.
Abstract: Anaerobic methane oxidation coupled to denitrification was recently assigned to bacteria belonging to the uncultured phylum NC10. In this study, we incubated sediment from a eutrophic ditch harboring a diverse community of NC10 bacteria in a bioreactor with a constant supply of methane and nitrite. After 6 months, fluorescence in situ hybridization showed that NC10 bacteria dominated the resulting population. The enrichment culture oxidized methane and reduced nitrite to dinitrogen gas. We assessed NC10 phylum diversity in the inoculum and the enrichment culture, compiled the sequences currently available for this bacterial phylum, and showed that of the initial diversity, only members of one subgroup had been enriched. The growth of this subgroup was monitored by quantitative PCR and correlated to nitrite-reducing activity and the total biomass of the culture. Together, the results indicate that the enriched subgroup of NC10 bacteria is responsible for anaerobic methane oxidation coupled to nitrite reduction. Due to methodological limitations (a strong bias against NC10 bacteria in 16S rRNA gene clone libraries and inhibition by commonly used stopper material) the environmental distribution and importance of these bacteria could be largely underestimated at present.

395 citations

Journal ArticleDOI
TL;DR: The results obtained extend the concept that the anammox bacteria can be enriched to high densities in the presence of substrates for heterotrophic growth by indicating that Candidatus 'Brocadia fulgida' did not incorporate acetate directly into their biomass.
Abstract: Anaerobic ammonium oxidizing (anammox) bacteria are detected in many natural ecosystems and wastewater treatment plants worldwide. This study describes the enrichment of anammox bacteria in the presence of acetate. The results obtained extend the concept that the anammox bacteria can be enriched to high densities in the presence of substrates for heterotrophic growth. Batch experiments showed that among the tested biomass, the biomass from the Candidatus 'Brocadia fulgida' enrichment culture oxidizes acetate at the highest rate. Continuous cultivation experiments showed that in the presence of acetate, ammonium, nitrite and nitrate, Candidatus 'Brocadia fulgida' out-competed other anammox bacteria. The results indicated that Candidatus 'Brocadia fulgida' did not incorporate acetate directly into their biomass. Candidatus 'Brocadia fulgida' exhibited the common characteristics of anammox bacteria: the presence of an anammoxosome and ladderane lipids and the production of hydrazine in the presence of hydroxylamine. Interestingly, the biofilm aggregates of this species showed strong autofluorescence. It is the only known anammox species exhibiting this feature. The autofluorescent extracellular polymeric substance had two excitation (352 and 442 nm) and two emission (464 and 521 nm) maxima.

385 citations

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202122
202027
201941
201848
201752
201641