Exploration of intraclonal adaptation mechanisms of Pseudomonas brassicacearum facing cadmium toxicity

Pseudomonas brassicacearum forms phenotypic variants in vitro as well as in planta during root colonization under natural conditions, leading to subpopulations (phase I and II cells) that differ in colony morphology and production of exoenzymes/secondary metabolites. The maximal concentration of cadmium allowing both variants growth was 25 μM; however, phase II cells accumulated fivefold higher Cd than phase I cells, even though both variants showed the same growth rate and kinetics, comprising a long stasis period (50 h). The whole transcriptome analysis of both variants in response to Cd was investigated using the home-made DNA microarrays. This analysis revealed completely different adaptation mechanisms developed by each variant to withstand and grow in the presence of the toxic. A re-organization of the cell wall to limit Cd entrance was noticed for phase I cells, as genes encoding levan exopolymers were downregulated at the expense of an upregulation of genes encoding alginate, and an upregulation of transporters such as cadA, and a downregulation of copper transporters. Phase II cells were unable to prevent Cd entrance and recruited genes under the control of oxyR and soxR regulation to face osmotic and oxidant stresses generated by Cd. Putrescine and spermidine metabolism appeared to play a central role in Cd tolerance. Microarray data were validated by biological analyses such as motility, oxidative stress assay, metabolite profiling with ICR-FT/MS and UPLC, capillary electrophoresis analysis of biogenic amines

Observation of the Curie Transition in Palladium Bionanomaterial Using Muon Spin Rotation Spectroscopy

Palladium bionanomaterial was manufactured using the sulfate-reducing bacterium, Desulfovibrio desulfuricans, to reduce soluble Pd(II) ions to cell-bound Pd(0). The material was examined using a Superconducting Quantum Interference Device (SQUID) to observe bulk magnetisation over the temperature range 10 – 300 K and by Muon Spin Rotation (μSR), which is a probe of the local magnetic environment inside the sample, over the temperature range 200 – 700 K. Results from SQUID were used to model the temperature dependence of ferromagnetic and paramagnetic components of the bulk magnetisation and, by extrapolation, to predict the Curie transition temperature. Results from μSR confirmed the accuracy of the prediction to within 20 K. The Curie transition, which started at 528 K, was shown to be spread over a wide ( 100 K) range. This was attributed to dependence of the transition on particle size and the range of particle sizes in the population. A competing contribution to the overall magnetisation was observed due to partial thermal decomposition of the organic component of the material. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3533

Nanoparticles of palladium supported on bacterial biomass : new re-usable heterogeneous catalyst with comparable activity to homogeneous colloidal Pd in the Heck reaction

AbstractThe Heck coupling of iodobenzene with ethyl acrylate or styrene was used to assess the catalytic properties of biogenic nanoparticles of palladium supported upon the surface of bacterial biomass (bioPd), this approach combining advantages of both homogeneous and heterogeneous catalysts. The biomaterial was comparably active or superior to colloidal Pd in the Heck reaction, giving a final conversion of 85% halide and initial rate of 0.17mmol/min for the coupling of styrene and iodobenzene compared to a final conversion of 70% and initial rate of 0.15mmol/min for a colloidal Pd catalyst under the same reaction conditions at 0.5mol.% catalyst loading. It was easily separated from the products under gravity or by filtration for reuse with low loss or agglomeration. When compared to two alternative palladium catalysts, commercial 5% Pd/C and tetraalkylammonium-stabilised palladium clusters, the bioPd was successfully reused in six sequential alkylations with only slight decreases in the rate of reaction as compared to virgin catalyst (initial rate normalised for g Pd decreased by 5% by the 6th run with bioPd catalyst cf. a decrease of 95% for Pd/C). A re-usable Pd-catalyst made cheaply from bacteria left over from other processes would impact on both conservation of primary sources via reduced metal losses in industrial application and the large environmental demand of primary processing from ores

Continuous removal of Cr(VI) from aqueous solution catalysed by palladised biomass of <i>Desulfovibrio vulgaris</i>

Growth-decoupled cells of Desulfovibrio vulgaris NCIMB 8303 can be used to reduce Pd(II) to cell-bound Pd(0) (Bio-Pd0), a bioinorganic catalyst capable of reducing hexavalent chromium to less toxic Cr(III), using formate as the electron donor. Magnetic resonance imaging showed that Bio-Pd0, immobilized in chitosan and agar beads, is distinguishable from the surrounding gel and is evenly dispersed within the immobilization matrix. Agar-immobilized Bio-Pd0 and `chemical Pd0' were packed into continuous-flow reactors, and challenged with a solution containing 100 μm Cr(VI) (pH 7) at a flow rate of 2.4 ml h−1. Agar-immobilized chemical Pd0 columns lost Cr(VI) reducing ability by 160 h, whereas columns containing immobilized Bio-Pd0 maintained 90% reduction until 680 h, after which reduction efficiency was gradually lost

Biorecovery of uranium from aqueous solutions at the expense of phytic acid

Perceived environmental problems of nuclear fuel fabrication, use and treatment limit the acceptability of nuclear power as an alternative to fossil fuels. This applies to nuclear fuel processing and reprocessing but contamination also occurs at source via run-offs from current and historic mining activities. The price of uranium (U3O8) in the1990s was US$10/lb but is currently US$58/lb, peaking in 2007 at US$135/lb. With the potential global expansion of nuclear power as an alternative to fossil fuels the market and strategic values of U will rise. A new biotechnology was demonstrated for efficient recovery of U from mine waters as pure hydrogen uranyl phosphate (HUP) but an economic assessment (discounting the value of U) showed that the limitation as a waste treatment process was the cost of the phosphate feed supplement which contained 1 mol/mol phosphate. We describe the use of phytic acid (inositol phosphate; 6 mol phosphate/mol), a ubiquitous plant waste, to support the removal of uranium as HUP by an immobilised cell reactor and shift the focus away from bioremediation to value product manufacturing from wastes, and resource efficiency