Impact of a novel protein meal on the gastrointesinal microbiota and host transciptome of larval zebrafish Danio rerio
Rurangwa, E. ; Sipkema, D. ; Kals, J. ; Veld, M. ter; Forlenza, M. ; Bacanu, G.M. ; Smidt, H. ; Palstra, A.P. - \ 2015
Frontiers in Physiology 6 (2015). - ISSN 1664-042X - 27 p.
large gene lists - intestinal microbiota - gut microbiota - digestive physiology - solea-senegalensis - metal uptake - sp-nov - fish - expression - iron
Larval zebrafish was subjected to a methodological exploration of the gastrointestinal microbiota and transcriptome. Assessed was the impact of two dietary inclusion levels of a novel protein meal (NPM) of animal origin (ragworm Nereis virens) on the gastrointestinal tract (GIT). Microbial development was assessed over the first 21 days post egg fertilisation (dpf) through 16S rRNA gene-based microbial composition profiling by pyrosequencing. Differentially expressed genes in the GIT were demonstrated at 21 dpf by whole transcriptome sequencing (mRNAseq). Larval zebrafish showed rapid temporal changes in microbial colonization but domination occurred by one to three bacterial species generally belonging to Proteobacteria and Firmicutes. The high iron content of NPM may have led to an increased relative abundance of bacteria that were related to potential pathogens and bacteria with an increased iron metabolism. Functional classification of the 328 differentially expressed genes indicated that the GIT of larvae fed at higher NPM level was more active in transmembrane ion transport and protein synthesis. mRNAseq analysis did not reveal a major activation of genes involved in the immune response or indicating differences in iron uptake and homeostasis in zebrafish fed at the high inclusion level of NPM
Considerations on the shuttle mechanism of FeEDDHA chelates at the soil-root interface in case of Fe deficiency
Schenkeveld, W.D.C. ; Reichwein, A.M. ; Temminghoff, E.J.M. ; Riemsdijk, W.H. van - \ 2014
Plant and Soil 379 (2014)1-2. - ISSN 0032-079X - p. 373 - 387.
strategy i plants - calcareous soil - lolium-perenne - metal uptake - iron uptake - complexes - eddha - chlorosis - isomers - montmorillonite
A mechanism of action for the performance of Fe chelates as soil-applied fertilizer has been hypothesized by Lindsay and Schwab (J Plant Nutr 5:821-840, 1982), in which the ligand participates in a cyclic process of delivering Fe at the root surface and mobilizing Fe from the soil. This "shuttle mechanism" seems appealing in view of fertilizer efficiency, but little is known about its performance. The chelate FeEDDHA is a commonly used Fe fertilizer on calcareous soils. In this study, the performance of the shuttle mechanism has been examined for FeEDDHA chelates in soil interaction and pot trial experiments. The specificity of EDDHA ligands for chelating Fe from soils of low Fe availability is limited. Experimental support for a shuttle mechanism in soil-plant systems with FeEDDHA was found: specific metal mobilization only occurred upon FeEDDHA-facilitated Fe uptake. The mobilized metals originated at least in part from the root surface instead of the soil. The results from this study support the existence of a shuttle mechanism with FeEDDHA in soil application. If the efficiency of the shuttle mechanism is however largely controlled by metal availability in the bulk soil, it is heavily compromised by complexation of competing cations: Al, Mn and particularly Cu.
The impact of the transient uptake flux on bioaccumulation : Linear adsorption and first-order internalisation coupled with spherical semi-infinite mass transport
Galceran, J. ; Monné, J. ; Puy, J. ; Leeuwen, H.P. van - \ 2004
Marine Chemistry 85 (2004)1-2. - ISSN 0304-4203 - p. 89 - 102.
green-alga - marine-phytoplankton - speciation dynamics - surface reaction - biotic ligand - silver uptake - metal uptake - diffusion - bioavailability - kinetics
The uptake of a chemical species (such as an organic molecule or a toxic metal ion) by an organism is modelled considering linear pre-adsorption followed by a first-order internalisation. The active biosurface is supposed to be spherical or semi-spherical and the mass transport in the medium is diffusion-controlled. The analytical solutions for the transient flux and accumulated amounts can be used to discriminate between adsorption and internalisation parameters, which are inseparable in a steady-state flux interpretation. The concentration at the surface of the organism and the (intracellular) uptake flux pass through a maximum before coming to their steady-state values. For any combination of the parameters, the time necessary to reach a diffusive flux, which differs by less than 10% from the eventual steady-state value, can be directly read from a contour plot. For small microorganisms, steady state is usually achieved in a short time and so the usual analysis based on the steady-state flux is a good approximation (except for combinations of large radii, low diffusion coefficients, important adsorption and slow internalisation kinetics). However, interpretation of the cumulative uptake requires (explicit or implicit) consideration of the large transient fluxes arising at short times. By considering an instantaneous steady state approximation, the linear regression of accumulation data outside the transient regime, i.e. at larger measuring times, allows for the discrimination between adsorption and kinetic parameters for small organisms as shown with literature data of lead uptake by Chlorella vulgaris.