Heterotrophic Nitrification and Aerobic Denitrification in Alcaligenes-Faecalis Strain TUD

Biological Anaerobic Ammonium Oxidation

Anaerobic ammonium oxidation in an estuarine sediment

The occurrence and significance of the anammox (anaerobic ammonium oxidation) process relative to denitrification was studied in photosynthetically active sediment from 2 shallow-water estuaries: Randers Fjord and Norsminde Fjord, Denmark. Anammox accounted for 5 to 24% of N2 production in Randers Fjord sediment, whereas no indication was seen...

Aerobic granular sludge: Scaling up a new technology

Most conventional wastewater treatment plants need a large surface area for the treatment of their sewage. This is due to the open structure of the biomass used to convert the polluting components in wastewater. Because of the flocculated growth, sludge concentrations in reaction tanks are low and settling times need to be long in order to keep...

Dynamics of Nitric Oxide and Nitrous Oxide Emission during Nitrogen Conversion Processes

Nitric oxide (NO) and nitrous oxide (N2O) emissions can be a serious threat to the environment. Rising levels of N2O in the atmosphere contribute to global warming and destruction of the ozone layer. This thesis describes an investigation on the emission of NO and N2O during nitrogen conversion processes. Emissions were measured at wastewater...

Biological Nutrient Removal in Compact Biofilm Systems

The removal of nutrients such as nitrogen and phosphorus from both domestic and industrial wastewaters is imperative since they potentially harm the environment. One of the main consequences of excessive availability of nitrogen and phosphorus in aquatic ecosystems (freshwater, marine and estuarine) is the overgrowth of algae and other aquatic...

Metabolic modeling of denitrification in Agrobacterium tumefaciens: A tool to study inhibiting and activating compounds for the denitrification pathway

A metabolic network model for facultative denitrification was developed based on experimental data obtained with Agrobacterium tumefaciens. The model includes kinetic regulation at the enzyme level and transcription regulation at the enzyme synthesis level. The objective of this work was to study the key factors regulating the metabolic response...

Metabolic modeling of denitrification in Agrobacterium tumefaciens: A tool to study inhibiting and activating compounds for the denitrification pathway

DNRA and Denitrification Coexist over a Broad Range of Acetate/N-NO3− Ratios, in a Chemostat Enrichment Culture

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) compete for nitrate in natural and engineered environments. A known important factor in this microbial competition is the ratio of available electron donor and elector acceptor, here expressed as Ac/N ratio (acetate/nitrate-nitrogen). We studied the impact of the Ac/N ratio...

Fermentative Bacteria Influence the Competition between Denitrifiers and DNRA Bacteria

Denitrification and dissimilatory reduction to ammonium (DNRA) are competing nitrate-reduction processes that entail important biogeochemical consequences for nitrogen retention/removal in natural and man-made ecosystems. The nature of the available carbon source and electron donor have been suggested to play an important role on the outcome of...

Role of nitrite in the competition between denitrification and DNRA in a chemostat enrichment culture

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two microbial processes that compete for oxidized nitrogen compounds in the environment. The objective of this work was to determine the role of nitrite versus nitrate as terminal electron acceptor on the competition between DNRA and denitrification. Initially, a mixed...

Metagenomic potential for and diversity of N-cycle driving microorganisms in the Bothnian Sea sediment

The biological nitrogen cycle is driven by a plethora of reactions transforming nitrogen compounds between various redox states. Here, we investigated the metagenomic potential for nitrogen cycle of the in situ microbial community in an oligotrophic, brackish environment of the Bothnian Sea sediment. Total DNA from three sediment depths was...

On the ecology of dissimilatory nitrate reduction to ammonium

The anthropogenic nitrogen inputs in the environment exceed the input by natural processes and impact the global nitrogen cycle considerably . Human meddling in the N-cycle occurs mainly in agricultural ecosystems. Loss of nitrogen from the agricultural soils, other than crop harvest, can have polluting effects on other environments. The three...

Wenzhouxiangella Strain AB-CW3, a Proteolytic Bacterium From Hypersaline Soda Lakes That Preys on Cells of Gram-Positive Bacteria

A new haloalkaliphilic species of Wenzhouxiangella, strain AB-CW3, was isolated from a system of hypersaline alkaline soda lakes in the Kulunda Steppe using cells of Staphylococcus aureus as growth substrate. AB-CW3’s complete, circular genome was assembled from combined nanopore and Illumina sequencing and its proteome was determined for...

How Important is Denitrification in Riparian Zones? Combining End-Member Mixing and Isotope Modeling to Quantify Nitrate Removal from Riparian Groundwater

Riparian zones are important buffer zones for streams as they are hotspots of nitrate transformation and removal in agricultural catchments. However, mixing of water from different sources and various transformation processes can complicate the quantification of nitrate turnover in riparian zones. In this study, we analyzed nitrate...

Cyclic Conversions in the Nitrogen Cycle

The cyclic nature of specific conversions in the nitrogen cycle imposes strict limitations to the conversions observed in nature and explains for example why anaerobic ammonium oxidation (anammox) bacteria can only use nitrite – and not nitrate – as electron acceptor in catabolism, and why nitrite is required as additional electron donor for...

Understanding nitrogen transformation using the ratio of nitrogen to argon in landfills under in-situ stabilisation

In the Netherlands, three full-scale pilots have been in operation for approximately five years to understand the effects of leachate recirculation or aeration on waste stabilisation. This study employs the ratio of N2 to Ar in the landfill gas in comparison to the ratio in atmospheric air to derive the share of N2 that originates from...