SciCombinator

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Concept: Photobacterium phosphoreum

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The individual toxicities of Cu and 11 nitroaromatic compounds to Photobacterium phosphoreum were determined. The toxicity was expressed as the concentrations causing a 50% inhibition of bioluminescence after 15min exposure (IC(50)). To evaluate the joint effect between the metal ion and the 11 nitroaromatic compounds, the joint toxicity of Cu and 11 nitroaromatic compounds were measured at different Cu concentrations (0.2IC(50), 0.5IC(50) and 0.8IC(50)), respectively. The result shows that the binary joint effect between Cu and nitroaromatic compounds is mainly simple addition at the low Cu concentration (0.2IC(50)). However, an antagonism effect, 55% and 64%, was observed between Cu and 11 nitroaromatic compounds for Cu at medium and high concentrations (0.5IC(50) and 0.8IC(50)). Quantitative structure-activity relationship (QSAR) analysis was performed to study the joint toxicity for the 11 nitroaromatic compounds. The result shows that the toxicity of nitroaromatic compounds is related to descriptors of Connolly solvent-excluded volume (CSEV) and dipolarity/polarizability (S) at low Cu concentration. On the other hand, the toxicity is related to Connolly accessible area (CAA) at medium and high Cu concentrations. The result indicates that different QSAR models on complex mixtures need to be developed to assess the ecological risk in real environments. Using single toxic data to evaluate the toxic effect of mixtures may result in wrong conclusions.

Concepts: Toxicology, Copper, Chemical compound, Toxicity, Medicinal chemistry, Quantitative structure-activity relationship, Structure-activity relationship, Photobacterium phosphoreum

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We demonstrated the possibility of long-term and efficient application of a biosensitive element (BE) in the form of Photobacterium phosphoreum photobacteria immobilized in poly(vinyl alcohol) (PVA) cryogel for detecting various ecotoxicants (Zn(2) (+) , Cu(2) (+) , Hg(2) (+) , Pb(2) (+) , 2,4-dichlorophenoxyacetic acid, 2,6-dimethylphenol, pentachlorophenol, coumaphos, malathion, chlorpyrifos and methyl parathion) in flow-through media. The range of detectable concentrations of ecotoxicants was determined at 1 × 10(-8) to 1 × 10(-4) M for heavy metal ions and at 1 × 10(-8) to 1 × 10(-5) M for phenol derivatives and organophosphorus pesticides. Immobilized cells of photobacteria quantitatively reacted with these ecotoxicants; cell sensitivity exhibited no flow rate dependence in the range from 45 to 180 mL/h. At a constant concentration of ecotoxicant in the flow, the bioluminescence quenching profile of immobilized cells demonstrated an integral response. The BE could remain in a flow-through medium for at least 10 days while retaining 95% of luminescent activity in the absence of ecotoxicants. The BE tested in this work was demonstrated to have a long shelf life (> 60 weeks) at -80°C without changes in the baseline level of bioluminescence. Copyright © 2016 John Wiley & Sons, Ltd.

Concepts: Concentration, Chemistry, Metal, Heavy metal music, Organophosphate, Insecticide, Bioluminescence, Photobacterium phosphoreum

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The occurrence of benzophenone-4 (BP-4) in water environments may pose a serious public health hazard due to its potential endocrine disrupting effects. In this work, the intermediates, probable degradation pathways and toxicity changes during ozonation of BP-4 in aqueous solution were systematically investigated. Results revealed that alkaline conditions favored the oxidation of BP-4. However, inorganic anions (Cl(-), NO3(-), SO4(2-)), cations (K(+), Ca(2+), Mg(2+)) and humic acid had no remarkable effect on BP-4 removal within the tested concentrations. Ozonation was also effective for the fast removal of BP-4 in real waters. The TOC suggested a low mineralization rate, even after the complete BP-4 removal. Meanwhile, the treated mixtures exhibited an obvious inhibition to the bioluminescent bacteria Photobacterium phosphoreum, indicating the formation of transformation products with higher toxicities. Furthermore, fourteen products were identified by means of liquid chromatography-mass spectrometry. Notably, seven of them have not been reported previously. The quenching test indicated that the degradation processes probably were dominated by OH. Next, possible degradation pathways were proposed and further justified by theoretical calculations of frontier electron densities. This investigation will contribute to the systematic elucidation of the ozonation process of UV filters in aquatic environments.

Concepts: Effect, Water, Effectiveness, Concentration, Chemistry, Aqueous solution, Bioluminescence, Photobacterium phosphoreum

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The individual IC50 (the concentrations causing a 50% inhibition of bioluminescence after 15min exposure) of cadmium ion (Cd) and nine chlorinated anilines to Photobacterium phosphoreum (P. phosphoreum) were determined. In order to evaluate the combined effects of the nine chlorinated anilines and Cd, the toxicities of chlorinated anilines combined with different concentrations of Cd were determined, respectively. The results showed that the number of chlorinated anilines manifesting synergy with Cd decreased with the increasing Cd concentration, and the number manifesting antagonism decreased firstly and then increased. The joint toxicity of mixtures at low Cd concentration was weaker than that of most binary mixtures when combined with Cd at medium and high concentrations as indicated by TUTotal. QSAR analysis showed that the single toxicity of chlorinated anilines was related to the energy of the lowest unoccupied molecular orbital (ELUMO). When combined with different concentrations of Cd, the toxicity was related to the energy difference (EHOMO-ELUMO) with different coefficients. Van der Waals' force or the complexation between chlorinated anilines and Cd had an impact on the toxicity of combined systems, which could account for QSAR models with different physico-chemical descriptors.

Concepts: Molecule, Electrochemistry, Concentration, Chemistry, Chemical equilibrium, Toxicology, Cadmium, Photobacterium phosphoreum

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The paper studies chronic effect of tritiated water, HTO, (0.0002-200 MBq/L) on bioluminescent assay systems: marine bacteria Photobacterium phosphoreum (intact and lyophilized) and coupled enzyme reactions. Bioluminescence intensity serves as a marker of physiological activity. Linear dependencies of bioluminescent intensity on exposure time or radioactivity were not revealed. Three successive stages in bacterial bioluminescence response to HTO were found: (1) absence of the effect, (2) activation, and (3) inhibition. They were interpreted in terms of reaction of organisms to stress-factor i.e. stress recognition, adaptive response/syndrome, and suppression of physiological function. In enzyme system, in contrast, the kinetic stages mentioned above were not revealed, but the dependence of bioluminescence intensity on HTO specific radioactivity was found. Damage of bacteria cells in HTO (100 MBq/L) was visualized by electron microscopy. Time of bioluminescence inhibition is suggested as a parameter to evaluate the bacterial sensitivity to ionizing radiation.

Concepts: DNA, Bacteria, Enzyme, Light, Fungus, Gamma ray, Bioluminescence, Photobacterium phosphoreum

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The integral bioluminescence (BL) intensity of live Photobacterium phosphoreum cells (strain 1883 IBSO), sampled at the stationary growth stage (20h), was monitored for further 300h in the absence (control) and presence of (241)Am (an α-emitting radionuclide of a high specific activity) in the growth medium. The activity concentration of (241)Am was 2kBql(-1); [(241)Am]=6.5×10(-11)M. Parallel experiments were also performed with water-soluble humic substances (HS, 2.5mgl(-1); containing over 70% potassium humate) added to the culture medium as a possible detoxifying agent. The BL spectra of all the bacterial samples were very similar (λ(max)=481±3nm; FWHM=83±3nm) showing that (241)Am (also with HS) influenced the bacterial BL system at stages prior to the formation of electronically excited states. The HS added per se virtually did not influence the integral BL intensity. In the presence of (241)Am, BL was initially activated but inhibited after 180h, while the system (241)Am+HS showed an effective activation of BL up to 300h which slowly decreased with time. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, applied to dry cell biomass sampled at the stationary growth phase, was used to control possible metabolic responses of the bacteria to the α-radioactivity stress (observed earlier for other bacteria under other stresses). The DRIFT spectra were all very similar showing a low content of intracellular poly-3-hydroxybutyrate (at the level of a few percent of dry biomass) and no or negligible spectroscopic changes in the presence of (241)Am and/or HS. This assumes the α-radioactivity effect to be transmitted by live cells mainly to the bacterial BL enzyme system, with negligible structural or compositional changes in cellular macrocomponents at the stationary growth phase.

Concepts: Bacteria, Enzyme, Microbiology, Yeast, Fourier transform, Growth medium, Bioluminescence, Photobacterium phosphoreum

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The paper considers effects of humic substances (HS), as natural attenuators of toxicity, on solutions of model inorganic pollutants, metal salts - Pb(NO(3))(2), СоСl(2), CuSO(4), Eu(NO(3))(3), СrСl(3), and K(3)[Fe(СN)(6)]. Luminous bacteria Photobacterium phosphoreum and bioluminescent system of coupled enzymatic reactions were used as bioassays to monitor toxicity of salt solutions. The ability of HS to decrease or increase toxicity was demonstrated. Detoxifying concentrations of HS were determined; detoxification coefficients were calculated at different times of exposure of salt solutions to HS. To study the combined effects of HS and salts on bioluminescent assay systems, the rates of biochemical reactions and bacterial ultrastructure were analyzed. The detoxifying effects were explained by: (1) decrease of free metal content in water solutions under metal-HS binding; (2) increase of biochemical reaction rates in a bioluminescent assay system under HS effect; (3) enhancement of mucous layers on cell surface as a response to unfavorable impact of toxicants. Detoxifying mechanisms (2) and (3) reveal the active role of bioassay systems in detoxification processes.

Concepts: Bacteria, Enzyme, Chemical reaction, Water, Chemistry, Salt, Bioluminescence, Photobacterium phosphoreum