96 research outputs found
Effects of limed manure digestate application in sandy soil on plant nitrogen availability and soil N2O emissions
Anaerobically-digested manure is frequently applied to agricultural soil to enhance plant growth and reduce the need for chemical fertilizers. This practice also stimulates microbial nitrogen transformations and often results in N2O emissions. A single mesophilic anaerobic digestion is insufficient for pathogen removal or inactivation and therefore, a post treatment is required for its stabilization and hygienization. Here, we examined the effects of limed manure-digestate as a nitrogen source for plant growth and on N2O emission compared with compost. A plant growth experiment was conducted in a sandy soil and N2O emissions were monitored throughout the experiment. Plants were irrigated with freshwater or liquid-N fertilizer. The combination of compost application and liquid-N fertilizer resulted in surface N2O fluxes over 0.7 âmg âmâ2 dâ1, which were correlated with ammonium concentration in the soil. The presence of N2O in the rhizosphere was only detected in compost-amended soil 2â10 days after plantation. A significantly-lower surface N2O flux of 0.4 âmg âmâ2 dâ1 was recorded with application of limed-digestate, probably due to its effects on nitrogen-transforming microorganisms. Both compost and limed-digestate enhanced plant growth, with a more distinct effect in the freshwater treatment. Our observations demonstrate that limed-digestate can be an efficient substitute for compost as it effectively supports plant growth with substantially-lower N2O emissions
Nitrogen Transformations and Diversity of Ammonia-Oxidizing Bacteria in a Desert Ephemeral Stream Receiving Untreated Wastewater
Specific detection of p-chlorobenzoic acid by Escherichia coli bearing a plasmid-borne fcbA':: lux fusion
Rozen Y, Nejidat A, Gartemann K-H, Belkin S. Specific detection of p-chlorobenzoic acid by Escherichia coli bearing a plasmid-borne fcbA':: lux fusion. CHEMOSPHERE. 1999;38(3):633-641.In this communication we report on a genetically engineered bacterium that reacts by light emission to the presence of 4-chlorobenzoic acid. To construct this strain, DNA fragment (1.7 kb) upstream from the 4-chlorobenzoic acid dehalogenase (fcb) operon of Arthrobacter SU was fused to Vibrio fischeri luxCDABE genes. An Escherichia coli strain transformed with a multi-copy plasmid (pASU) bearing this fusion responded to the presence of 4-chlorobenzoic acid and a few closely related compounds by increased luminescence, exhibiting a high specificity but a relatively low sensitivity. While it could be somewhat, improved by manipulating the experimental pH, sensitivity remained too low for real time applicability. Nevertheless, the principle of using dehalogenase promoters as environmental pollution sensor was demonstrated. (C) 1998 Elsevier Science Ltd. All rights reserved
Regulation of Stomatal Opening in Epidermal Strips of Commelina communis L. by Phytochrome
Transfer of the movement protein gene between two tobamoviruses: influence on local lesion development
International audienc
Controlling nitritation in a continuous split-feed/aeration biofilm nitrifying bioreactor
© 2019 Elsevier Ltd This study explored the stability of partial ammonium oxidation at low feed concentration (50 g N/m3), suitable for anammox process, in continuous fixed bed up-flow biofilm reactors with external recirculation-aeration. The reactors, filled with crushed basalt, were fed with synthetic medium at 20â25 °C at constant flow-rate with limiting dissolved oxygen concentration controlled by the recirculation ratio (R). Successful nitritation was achieved at R â
4â6 with approx. 50% of NH4+ oxidized to NO2- with <5% NO3-accumulation. q-PCR analysis along the reactor showed ammonia oxidizing bacteria being the prevalent nitrifiers over the three-fourths of the bed in the flow direction, negligible denitrifiers and absent ammonium oxidizing archaea. A numerical model for predicting the concentration of the nitrogen species and DO was formulated. The model successfully predicted the experimental results and displayed good sensitivity to intrinsic oxygen uptake parameters. The proposed numerical model can serve both as an operational and design tool
Viscoelastic Properties of Extracellular Polymeric Substances Can Strongly Affect Their Washing Efficiency from Reverse Osmosis Membranes
The
role of the viscoelastic properties of biofouling layers in
their removal from the membrane was studied. Model fouling layers
of extracellular polymeric substances (EPS) originated from microbial
biofilms of <i>Pseudomonas aeruginosa</i> PAO1 differentially
expressing the Psl polysaccharide were used for controlled washing
experiments of fouled RO membranes. In parallel, adsorption experiments
and viscoelastic modeling of the EPS layers were conducted in a quartz
crystal microbalance with dissipation (QCM-D). During the washing
stage, as shear rate was elevated, significant differences in permeate
flux recovery between the three different EPS layers were observed.
According to the amount of organic carbon remained on the membrane
after washing, the magnitude of Psl production provides elevated resistance
of the EPS layer to shear stress. The highest flux recovery during
the washing stage was observed for the EPS with no Psl. Psl was shown
to elevate the layerâs shear modulus and shear viscosity but
had no effect on the EPS adhesion to the polyamide surface. We conclude
that EPS retain on the membrane as a result of the layer viscoelastic
properties. These results highlight an important relation between
washing efficiency of fouling layers from membranes and their viscoelastic
properties, in addition to their adhesion properties
Studies of coat protein-mediated resistance to tobacco mosaic virus (TMV). II. Challenge by a mutant with altered virion surface does not overcome resistance conferred by TMV coat protein
Abundance and diversity of anammox bacteria in a mainstream municipal wastewater treatment plant
© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Among the factors that obstruct the application of anammox-based technology for nitrogen removal from mainstream municipal wastewater is the waterâs high organic loads. We hypothesized that some anammox species can adapt and grow in mainstream wastewater in which a minimal temperature of 13â15 °C is maintained. Using the AMX368F and AMX820R PCR-primers, anammox bacteria were detected in influent wastewater (COD/N ratio > 13) and in the anaerobic, anoxic, and aerobic chambers of a full-scale municipal wastewater treatment plant, reaching 107 copies/g VSS of the16S rRNA gene. Furthermore, anammox activity was demonstrated by 15N-isotopic tracing. The DNA sequences of clones randomly selected from a clone library were mainly clustered with Candidatus Brocadia flugida in addition to Ca. Brocadia sinica, Ca. Jettenia asiatica, and Ca. Anammoxoglobus propionicus. However, Ca. Brocadia was the only genus detected by high-throughput next-generation sequencing and denaturing gradient gel electrophoresis. The nitrite producers, ammonia-oxidizing archaea and bacteria, were both detected in the influent wastewater and the other chambers, while the nitrite consumers, Nitrospira nitrite oxidizers and the nirS-type denitrifiers, dominated all chambers. The results indicate the occurrence and potential activity of anammox bacteria in mainstream wastewater under certain conditions (proper temperature). The dominance of Brocadia flugida and Anammoxoglobus propionicus suggests a role for volatile fatty acids in selecting the anammox community in wastewater
- âŠ