MTs in Palaemonetes argentinus as potential biomarkers of zinc contamination in freshwaters

Aquatic invertebrates take up and accumulate essential and non-essential trace metals even when both are likely to be poisonous. In order to study the potential of the metallothioneins (MTs) as biomarkers of metal contamination in native shrimp Palaemonetes argentinus, organisms have been exposed at 0, 5, 50 and 500 μg L⁻¹ of zinc for 96 h. Moreover, accumulation and subcellular distribution of this essential metal were evaluated. A significant Zn accumulation was observed in different body sections. Higher Zn levels occurred in cephalothorax compared to abdomen, especially at the highest exposure concentration (500 μg Zn L⁻¹). A clear differential subcellular metal distribution between cephalothorax and abdomen was also observed. In cephalothorax Zn was similarly distributed between the soluble and insoluble fractions; while in abdomen, when total Zn increased, insoluble metal augmented more markedly than the soluble one. Cytosolic Zn levels increased more in cephalothorax than in abdomen of shrimps exposed to 500 μg Zn L⁻¹ when compared to control. Finally, a significant induction of MTs was observed in cephalothorax at 500 μg Zn L⁻¹. A potential role for MTs as biomarkers in P. argentinus should be further studied to enhance the sensitivity of the response, although it is likely that MTs play a key role in metal detoxification since the increase of these proteins is linked to metal challenge.     

Bioaccumulation and biochemical response in South American native species exposed to zinc: Boosted regression trees as novel tool for biomarkers selection

The aim of this study was to evaluate the response of a wide battery of biomarkers in two native species, the freshwater shrimp Palaemonetes argentinus and the macrophyte Potamogeton pusillus, experimentally exposed to zinc in order to establish the potential use of selected species as bioindicators of aquatic pollution. For this purpose, we propose the use of integrated biomarker index (IBR) with a previous selection of biomarkers using boosted regression trees (BRTs) as a new tool in ecotoxicology. Organisms were collected from a reference site, acclimated and exposed at relevant environmental zinc levels (control, 5, 50 and 500 μg Zn L⁻¹) for 96 h. Biomarkers were measured in cephalothorax and abdomen of shrimp as well as in leaf, stem and root of plants.Significant zinc accumulation was observed in cephalothorax of P. argentinus from 50 μg Zn L⁻¹ and from 5 μg Zn L⁻¹ in stem and root of P. pusillus, when compared with control condition. Those effect biomarkers with significant differences among treatments were pre-selected to run out the BRTs model for each species. In P. argentinus, microsomal acetylcholinesterase activity, metallothioneins and superoxide dismutase activity measured in cephalothorax, as well as glutathione reductase activity in abdomen, showed the higher capacity to explain or predict the zinc exposure concentration. On the contrary, in P. pusillus, only chlorophyll a measured in leaf and H₂O₂ measured in root were the more representative of exposure concentrations, at least, within the biomarkers tested in the present study. Thereafter, IBR was calculated with the selected biomarkers in P. argentinus and showed in a sole value the organism stress, which also correlates with zinc exposure and accumulation.Natives species tested displayed a sensitive response to metal exposure, which represents an important characteristic for biomonitoring programs. Our findings suggest that the BRTs and IBR are useful and robust run tools to select the better biomarkers in toxicological studies and indicate the organism stress.     

Chemical compositions and characteristics of organic compounds in propolis from Yemen

Propolis is a gummy material made by honeybees for protecting their hives from bacteria and fungi. The main objective of this study is to determine the chemical compositions and concentrations of organic compounds in the extractable organic matter (EOM) of propolis samples collected from four different regions in Yemen. The propolis samples were extracted with a mixture of dichloromethane and methanol and analyzed by gas chromatography–mass spectrometry (GC–MS). The results showed that the total extract yields ranged from 34% to 67% (mean = 55.5 ± 12.4%). The major compounds were triterpenoids (254 ± 188 mg g⁻¹, mainly α-, β-amyryl and dammaradienyl acetates), n-alkenes (145 ± 89 mg g⁻¹), n-alkanes (65 ± 29 mg g⁻¹), n-alkanoic acids (40 ± 26 mg g⁻¹), long chain wax esters (38 ± 25 mg g⁻¹), n-alkanols (8 ± 3 mg g⁻¹) and methyl n-alkanoates (6 ± 4 mg g⁻¹). The variation in the propolis chemical compositions is apparently related to the different plant sources. The compounds of these propolis samples indicate that they are potential sources of natural bio-active compounds for biological and pharmacological applications.     

Effect of Zinc nanoparticles on oxidative stress-related genes and antioxidant enzymes activity in the brain of Oreochromis niloticus and Tilapia zillii

This study was carried out to determine the median lethal concentrations (LC₅₀) of Zinc nanoparticles (ZnNPs) on Oreochromis niloticus and Tilapia zillii. The biochemical and molecular potential effects of ZnNPs (500 and 2000 μg L⁻¹) on the antioxidant system in the brain tissue of O. niloticus and T. zillii were investigated. Four hundred fish were used for acute and sub-acute studies. ZnNP LC₅₀ concentrations were investigated in O. niloticus and T. zillii. The effect of 500 and 2000 μg L⁻¹ ZnNPs on brain antioxidants of O. niloticus and T. zillii was investigated. The result indicated that 69 h LC₅₀ was 5.5 ± 0.6 and 5.6 ± 0.4 for O. nilotica and T. zillii, respectively. Fish exposed to 500 μg L⁻¹ ZnNPs showed a significant increase in reduced glutathione (GSH), total glutathione (tGSH) levels, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activity and gene expression. On the contrary, malondialdehyde (MDA) levels significantly decreased. Meanwhile, fish exposed to 2000 μg L⁻¹ ZnNPs showed a significant decrease of GSH, tGSH levels, SOD, CAT, GR, GPx and GST activity and gene expression. On the contrary, MDA levels significantly increased. It was concluded that, the 96 h LC₅₀ of ZnNPs was 5.5 ± 0.6 and 5.6 ± 0.4 for O. nilotica and T. zillii, respectively. ZnNPs in exposure concentrations of 2000 μg/L induced a deleterious effect on the brain antioxidant system of O. nilotica and T. zillii. In contrast, ZnNPs in exposure concentrations of 500 μg L⁻¹ produced an inductive effect on the brain antioxidant system of O. nilotica and T. zillii.     

Mercury levels assessment in hair of riverside inhabitants of the Tapajós River,Pará State,Amazon, Brazil: Fish consumption as a possible route of exposure

The study present evaluated the levels of mercury (Hg) and methylmercury (MeHg) in hair samples of people from Barreiras community, riverside inhabitants of the Tapajós River (Pará, Brazil), an area impacted by clandestine gold mining, as well as we analyzed the levels of Hg and Se (selenium) in nine fish species (carnivores and non-carnivorous) from the Tapajós River, which stand out as the main species consumed by riverside inhabitants, to evaluate a relationship between frequency of fish consumption and Hg concentration, and also to evaluate possible mechanisms of fish protection (or non-protection) to Hg exposure by Se. Furthermore we analyze the water quality to evaluate the environmental trophic state, fact responsible by creating conditions that can potentiate the effects of toxic mercury. Concentrations of Hg and MeHg were analyzed in hair samples of 141 volunteers in different age band. Of those, 84.40% of samples present values above the threshold for biological tolerance, which is 6.00 μg g⁻¹ of total Hg in hair. Total Hg, in men there was a variation of 2.07–24.93 μg g⁻¹, while for women the variation was 4.84–27.02 μg g⁻¹. Consequently, the level of MeHg in men presented a variation of 1.49–19.57 μg g⁻¹, with an average of 11.68 μg g⁻¹, while with women the variation was from 3.73 to 22.35 μg g⁻¹, with an average of 10.38 μg g⁻¹. In fish species, Hg concentrations in carnivorous species had an average of 0.66 μg g⁻¹, higher than that permitted by current legislation, ranging from 0.30 to 0.98 μg g⁻¹, while the non-carnivorous species have values below the recommended by the legislation averaging 0.09 μg g⁻¹, ranging between 0.02 and 0.44 μg g⁻¹. For Se in fish, show that among carnivores, the contents of Se ranged between 0.18 and 0.54 μg g⁻¹ with a mean of 0.34 μg g⁻¹, while for non-carnivores these values were of the order of 0.16–0.56 μg g⁻¹, with an average of 0.32 μg g⁻¹. In surface water quality variables at the sampling points all showed values in accordance with the range established by current legislation. In this regard, the results provided by this study, while not conclusive, are strong indicators that despite not having been shown the relationship between the concentration of mercury in hair and feeding habits along the Tapajós River basin communities showed that a plausible correlation exists between levels of mercury and selenium in fish. This fact may serve as a subsidy to research human health, because in the Amazon, there is still a lot to examine with regards to the full understanding of the Se cycle.     

The effects of NH4+ and NO3− on growth,resource allocation and nitrogen uptake kinetics of Phragmites australis and Glyceria maxima

The effects of NH₄⁺ or NO₃⁻ on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g⁻¹ d⁻¹), whereas the growth rate of Glyceria was 16% higher in NH₄⁺-N cultures than in NO₃⁻-N cultures (mean = 66.7 and 57.4 mg g⁻¹ d⁻¹ of NH₄⁺ and NO₃⁻ treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH₄⁺ cultures than in NO₃⁻ cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH₄⁺ treated plants by 16%. The tissue NH₄⁺ concentration (mean = 1.6 μmol g fresh wt⁻¹) was not affected by N treatment, whereas NO₃⁻ contents were higher in NO₃⁻ (mean = 1.5 μmol g fresh wt⁻¹) than in NH₄⁺ (mean = 0.4 μmol g fresh wt⁻¹) treated plants. In Phragmites, NH₄⁺ (mean = 1.6 μmol g fresh wt⁻¹) and NO₃⁻ (mean = 0.2 μmol g fresh wt⁻¹) contents were not affected by the N regime. Species did not differ in NH₄⁺ (mean = 56.5 μmol g⁻¹ root dry wt h⁻¹) and NO₃⁻ (mean = 34.5 μmol g⁻¹ root dry wt h⁻¹) maximum uptake rates (V_max), and V_max for NH₄⁺ uptake was not affected by N treatment. The uptake rate of NO₃⁻ was low in NH₄⁺ treated plants, and an induction phase for NO₃⁻ was observed in NH₄⁺ treated Phragmites but not in Glyceria. Phragmites had low K_m (mean = 4.5 μM) and high affinity (10.3 l g⁻¹ root dry wt h⁻¹) for both ions compared to Glyceria (K_m = 6.3 μM, affinity = 8.0 l g⁻¹ root dry wt h⁻¹). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH₄⁺-N source may participates in the observed success of Glyceria at NH₄⁺ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites.     

Seasonal variations in photosynthetic irradiance response curves of macrophytes from a Mediterranean coastal lagoon

The main photosynthesis and respiration parameters (dark respiration rate, light saturated production rate, saturation irradiance, photosynthetic efficiency) were measured on a total of 23 macrophytes of the Thau lagoon (2 Phanerogams, 5 Chlorophyceae, 10 Rhodophyceae and 6 Phaeophyceae). Those measurements were performed in vitro under controlled conditions, close to the natural ones, and at several seasons. Concomitantly, measurements of pigment concentrations, carbon, phosphorous and nitrogen contents in tissues were performed. Seasonal intra-specific variability of photosynthetic parameters was found very high, enlightening an important acclimatation capacity. The highest photosynthetic capacities were found for Chlorophyceae (e.g. Monostroma obscurum thalli at 17 °C, 982 μmol O₂ g⁻¹ dw h⁻¹ and 9.1 μmol O₂ g⁻¹ dw h⁻¹/μmol photons m⁻² s⁻¹, respectively for light saturated net production rate and photosynthetic efficiency) and Phanerogams (e.g. Nanozostera noltii leaves at 25 °C, 583 μmol O₂ g⁻¹ dw h⁻¹ and 2.6 μmol O₂ g⁻¹ dw h⁻¹/μmol photons m⁻² s⁻¹ respectively for light saturated net production rate and photosynthetic efficiency). As expected, species with a high surface/volume ratio were found to be more productive than coarsely branched thalli and thick blades shaped species. Contrary to R_d (ranging 6.7–794 μmol O₂ g⁻¹ dw h⁻¹, respectively for Rytiphlaea tinctoria at 7 °C and for Dasya sessilis at 25 °C) for which a positive relationship with water temperature was found whatever the species studied, the evolution of P/I curves with temperature exhibited different responses amongst the species. The results allowed to show summer nitrogen limitation for some species (Gracilaria bursa-pastoris and Ulva spp.) and to propose temperature preferences based on the photosynthetic parameters for some others (N. noltii, Zostera marina, Chaetomorpha linum).     

Dispersal pattern of airborne emissions from an aluminium smelter in Ouro Preto,Brazil, as expressed by foliar fluoride accumulation in eight plant species

In order to evaluate the dispersal pattern of airborne fluoride emissions, from a single source in the city of Ouro Preto, Brazil, the fluoride impact on some herbaceous plant species was studied using the plants as passive bioindicators. Foliar fluoride contents of eight species collected at different distances from an aluminium smelter were analyzed. The plant species were: Baccaharis dracunculifolia, Bidens pilosa, Borreria verticillata, Calopogonium mucunoides, Erigeron bonariensis, Hedychium coronarium, Ipomoea purpurea and Ipomoea cairica. In all species the fluoride accumulation decreased exponentially with the distance from the emission source. There was specific and distinct variation in fluoride accumulation among the species, a group of high-accumulator species (B. dracunculifolia and Bidens pilosa) and a group of low-accumulator species (I. cairica, H. coronarium and Borreria verticillata). C. mucunoides and E. bonariensis occupied an intermediate position. There was a pattern of plant contamination response during the periods analyzed. The plants nearest to the emission source, between 0.4 km northwest and 1.1 km east, showed fluoride contamination traits in leaves reaching values between 100 and 500 μg g⁻¹. Moreover, fluoride contents higher than 1000 μg g⁻¹ were found in these plants. At the most distant stations, situated 2.9 km northwest and 6 km east from the factory, the fluoride content of the dry matter was less than 10 μg g⁻¹ showing that plants at those distances were submitted to minimum contamination. There were different patterns of tolerance among the species analyzed. While B. dracunculifolia accumulated fluoride up to 1500 μg g⁻¹ in dry matter without any signs of injury, Borreria verticillata showed severe necrosis in leaves, but the fluoride content found was not higher than 120 μg g⁻¹.     

Peel of araticum fruit (Annona crassiflora Mart.) as a source of antioxidant compounds with α-amylase, α-glucosidase and glycation inhibitory activities

Annona crassiflora Mart., whose fruit is popularly known as araticum, is a member of the Annonaceae family found in the Brazilian Cerrado. Although this plant has several medicinal uses, its bioactive molecules are not fully understood. A bioguided assay was performed to identify the main bioactive compounds of A. crassiflora fruit peel from the ethanol extract fractions with antioxidant capacity and α-amylase, α-glucosidase and glycation inhibitory activities. Ethyl acetate and n-butanol fractions showed, respectively, higher antioxidant capacity (DPPH IC₅₀ 1.5 ± 0.1 and 0.8 ± 0.1 μg mL⁻¹, ORAC 3355 ± 164 and 2714 ± 79 μmol trolox eq/g, and FRAP 888 ± 16 and 921 ± 9 μmol trolox eq/g) and inhibitory activities against α-amylase (IC₅₀ 4.5 ± 0.8 and 1.7 ± 0.3 μg mL⁻¹), α-glucosidase (IC₅₀ 554.5 ± 158.6 and 787.8 ± 140.6 μg mL⁻¹) and glycation (IC₅₀ 14.3 ± 3.3 and 16.0 ± 4.2 μg mL⁻¹), and lower cytotoxicity, compared to the other fractions and crude ethanol extract. The HPLC-ESI-MS/MS analysis identified various biomolecules known as potent antioxidants, such as chlorogenic acid, (epi)catechin, procyanidins, caffeoyl-hexosides, quercetin-glucosides and kaempferol. The fruit peel of A. crassiflora, a specie from Cerrado, the Brazilian Savanna, provided a source of antioxidant compounds with properties to block carbohydrate digestive enzymes and formation of glycation products. Thus, there is potential to use the by-products of araticum in order to identify and isolate phytochemicals for application in nutraceutical supplements, food additives and pharmaceuticals products.     

Galactose-limited fed-batch cultivation of Escherichia coli for the production of lacto-N-tetraose

Lacto-N-tetraose (Gal(β1-3)GlcNAc(β1-3)Gal(β1-4)Glc) is one of the most abundant oligosaccharide structures in human milk. We recently described the synthesis of lacto-N-tetraose by a whole-cell biotransformation with recombinant Escherichia coli cells. However, only about 5% of the lactose was converted into lacto-N-tetraose by this approach. The major product obtained was the intermediate lacto-N-triose II (GlcNAc(β1-3)Gal(β1-4)Glc).In order to improve the bioconversion of lactose to lacto-N-tetraose, we have investigated the influence of the carbon source on the formation of lacto-N-tetraose and on the intracellular availability of the glycosyltransferase substrates, UDP-N-acetylglucosamine and UDP-galactose. By growth of the recombinant E. coli cells on D-galactose, the yield of lacto-N-tetraose (810.8 mg L⁻¹ culture) was 3.6-times higher compared to cultivation on D-glucose.Using fed-batch cultivation with galactose as sole energy and carbon source, a large-scale synthesis of lacto-N-tetraose was demonstrated. During the 26 h feeding phase the growth rate (μ = 0.05) was maintained by an exponential galactose feed. In total, 16 g L⁻¹ lactose were fed and resulted in final yields of 12.72 ± 0.21 g L⁻¹ lacto-N-tetraose and 13.70 ± 0.10 g L⁻¹ lacto-N-triose II. In total, 173 g of lacto-N-tetraose were produced with a space-time yield of 0.37 g L⁻¹ h⁻¹.     

Effects of phosphorus and nitrogen amendments on the growth of Egeria najas

The effect of nutrient addition on the growth of E. najas was evaluated in a dose response experiment using sand amended with phosphorus (P) and nitrogen (N), and in enrichment trials with N and P amendments to natural sediments. Plants, water and sediment came from lagoons of the Upper Paraná River Floodplain and from Itaipu Reservoir (Brazil). Relative growth rates (RGRs) of E. najas shoots, based on dry mass (DM), varied from 0.03 to 0.060 d⁻¹ for both nutrients. Root:shoot biomass ratios were related to sediment exchangeable P (r = −0.419; P = 0.03) and N (r = −0.54; P = 0.006), however root RGR was not related to sediment nutrient concentrations. When natural sediments were amended with N and P, neither shoot nor root RGRs differed among treatments for substrata from either the reservoir or the floodplain lagoons (P > 0.05). Comparison of nutrient concentrations measured in natural sediments collected from several sites in both the Upper Paraná River Floodplain (range 49–213 μg P g⁻¹ DM; 36–373 μg N g⁻¹ DM) and Itaipu Reservoir (range 43–402 μg P g⁻¹ DM; 7.9–238 μg N g⁻¹ DM) showed that sediment N and P from these systems usually exceeded minimum requirements necessary for E. najas growth, as measured in the dose response experiment. Together, these results indicate that E. najas, at least in early stages of development, responds to sediment nutrient amendments and relies upon bottom sediments to meet its N and P requirements and that for at least two Brazilian ecosystems, growth of this species is not limited by insufficient sediment N or P. Thus, reducing N and P in water is not enough to control E. najas growth in short time periods in these ecosystems.     

Signal transducer and oxidative stress mediated modulation of phenylpropanoid pathway to enhance rosmarinic acid biosynthesis in fungi elicited whole plant culture of Solenostemon scutellarioides

This study aimed to improve rosmarinic acid (RA) production in the whole plant culture of Solenostemon scutellarioides through elicitation with phytopathogenic fungi. Amongst selected fungi, Aternaria alternata caused significant elevation (p < 0.05–0.01) in RA accumulation (∼1.3–1.6-fold) between 25 and 100 μg l⁻¹. However, elicitation at the dose of 50 μg l⁻¹ has been found to be most effective and intracellular RA content reached almost ∼1.6-fold (p < 0.01) higher in day 7. Therefore, A. alternata (50 μg l⁻¹) was selected for mechanism evaluation. A significant elevation of intercellular jasmonic acid was observed up to day 6 after elicitation with A. alternata (50 μg l⁻¹). A significant increase in tissue H₂O₂ and lipid peroxidation coupled with depletion of antioxidant enzymes superoxide dismutase and catalase indicated augmented oxidative stress associated with biotic interaction. Preceding the elicitor-induced RA accumulation, a notable alteration in the specific activities of biosynthetic enzymes namely PAL and TAT was recorded, while, no significant change in the activities of RAS was observed. HPPR activity was slightly improved in elicited plant. Therefore, it could be concluded that A. alternata elicited the biosynthesis of rosmarinic acid via signal transduction through jasmonic acid coupled with elicitor induced oxidative stress and associated mechanism.     

Bench-scale fermentation of Trichoderma viride on wastewater sludge: Rheology,lytic enzymes and biocontrol activity

Conidiation and lytic enzyme production by Trichoderma viride at different solids concentration of pre-treated municipal wastewater sludge was examined in a 15-L fermenter. The maximum conidia concentration (5.94 × 10⁷ CFU mL⁻¹ at 96 h) was obtained at 30 g L⁻¹ suspended solids. The maximum lytic enzyme activities were achieved around 12–30 h of fermentation. Bioassay against a fungal phytopathogen, Fusarium sp. showed maximum activity in the sample drawn around 96 h of fermentation at 30 g L⁻¹ suspended solids concentration. Entomotoxicity against spruce budworm larvae showed maximum value ≈17290 SBU μL⁻¹ at 30 g L⁻¹ suspended solids concentration at the end of fermentation (96 h). Plant bioassay showed dual action of T. viride, i.e., disease prevention and growth promotion. The rheological analyses of fermentation sludges showed the pseudoplastic behaviour. In order to maintain required dissolved oxygen concentration ≥30%, the agitation and aeration requirements significantly increased at 35 g L⁻¹ compared to 30 and 25 g L⁻¹. The oxygen uptake rate and volumetric oxygen mass transfer coefficient, k_La at 35 g L⁻¹ did not increase in comparison to 30 g L⁻¹ due to rheological complexity of the broth during fermentation. Thus, the successful fermentation operation of the biocontrol fungus T. viride is a rational indication of its potential for mass-scale production for agriculture and forest sector as a biocontrol agent.     

Evaluation of distant carbon sources in biosurfactant production by a gamma ray-induced Pseudomonas putida mutant

Pseudomonas putida 33 wild strain, subjected to gamma ray mutagenesis and designated as P. putida 300-B mutant was used as microbial rhamnolipid-producer by using distant carbon sources (viz. hydrocarbons, waste frying oils ‘WFOs’, vegetable oil refinery wastes and molasses) in the minimal media under shake flask conditions. The behavior of glucose as co-substrate and growth initiator was examined. The 300-B mutant strain showed its ability to grow on all the substrates tested and produced rhamnolipid surfactants to different extents however; soybean and corn WFOs were observed to be preferred carbon sources followed by kerosene and paraffin oils, respectively. The best cell biomass (3.5 g l⁻¹) and rhamnolipids yield (4.1 g l⁻¹) were obtained with soybean WFO as carbon source and glucose as growth initiator under fed-batch cultivation showing an optimum specific growth rate (μ) of 0.272 h⁻¹, specific product yield (q_p) of 0.318 g g⁻¹ h and volumetric productivity (P_V) of 0.024 g l⁻¹ h. The critical micelle concentration of its culture supernatant was observed to be 91 mg rhamnolipids l⁻¹ and surface tension as 31.2 mN m⁻¹.     

The relationship between Pseudo-nitzschia (Peragallo) and domoic acid in Scottish shellfish

The diatom genus Pseudo-nitzschia (Peragallo) associated with the production of domoic acid (DA), the toxin reposnsible for amnesic shellfish poisoning, is abundant in Scottish waters. A two year study examined the relationship between Pseudo-nitzschia cells in the water column and DA concentration in blue mussels (Mytilus edulis) at two sites, and king scallops (Pecten maximus) at one site. The rate of DA uptake and depuration differed greatly between the two species with M. edulis whole tissue accumulating and depurating 7 μg g⁻¹ (now expressed as mg kg⁻¹) per week. In contrast, it took 12 weeks for DA to depurate from P. maximus gonad tissue from a concentration of 68 μg g⁻¹ (now mg kg⁻¹) to <20 μg g⁻¹ (now mg kg^‐1). The DA depuration rate from P. maximus whole tissue was <5% per week during both years of the study. Correlations between the Pseudo-nitzschia cell densities and toxin concentrations were weak to moderate for M. edulis and weak for P. maximus. Seasonal diversity on a species level was observed within the Pseudo-nitzschia genus at both sites with more DA toxicity associated with summer/autumn Pseudo-nitzschia blooms when P. australis was observed in phytoplankton samples. This study reveals the marked difference in DA uptake and depuration in two shellfish species of commercial importance in Scotland. The use of these shellfish species to act as a proxy for DA in the environment still requires investigation.     

Toxic and genotoxic effects of potassium dichromate in Pseudokirchneriella subcapitata detected by microscopy and AFLP marker analysis

The effect of chromium on Pseudokirchneriella subcapitata has been assessed using different approaches: growth rate, metabolic activity microscopy analyses, and amplified fragment length polymorphism (AFLP) assessment of DNA damage. Starting from 24 h of treatment all the tested concentrations resulted in consistent algal growth inhibition. The average daily growth rate after 72 h calculated for the control (0.53 ± 0.01) was statistically higher than those estimated for cell treated with 1, 2.5, 5 and 7.5 μg g⁻¹ potassium dichromate (0.46 ± 0.02; 0.32 ± 0.01; 0.25 ± 0.01 and −0.02 ± 0.04, respectively). A reduction of viable cell numbers, estimated with FDA approach, was also observed after 24 h treatment for all the tested chromium concentrations apart from the lowest (1 μg g⁻¹ potassium dichromate). A recovery of esterase activity was detected after 48 and 72 h for all treatments with the except of the 7.5 μg g⁻¹ potassium dichromate treated samples showing a very modest recovery. This data suggests that potassium dichromate is, even from the lowest tested concentration, highly toxic to P. subcapitata, and that this algal strain is a sensitive organism suitable for monitoring chromium in water. Our data also suggest that although algal counting by microscope and the FDA test gave similar indications concerning chromium effect, the FDA test was not completely reliable. In fact, we observed a decrease in the FDA stained cell numbers in control samples after 48 and 72 h of treatment, when most cells were actively proliferating. This lack of fluorescence could be explained by an uncontrolled fluorescein efflux due to the interaction of many experimental factors. The genotoxic effects of the different chromium concentrations were investigated by analyses of the DNA from control and treated algal samples, 72 h after inoculation. AFLP analysis revealed a total of 258 bands, 109 of which were polymorphics. Analysis of the AFLP matrix suggests that potassium dichromate is a powerful genotoxic agent, inducing genetic mutations also at the lowest tested concentration (0.35 μg g⁻¹). Furthermore, we observed a correlation between the polymorphic bands with increasing chromium concentration. Finally, the absence of preferential mutation sites suggests that the chromium induced DNA changes are randomly distributed in the genome.     

Insecticidal properties of Pimpinella anisum essential oils against the Culex quinquefasciatus and the non-target organism Daphnia magna

The efficacy of an essential oil obtained from Pimpinella anisum fruits and its major compound, trans-Anethole, was tested on the eggs, larvae and adults of Culex quinquefasciatus. While causing no significant mortality on eggs, other tested stages were very sensitive to the essential oil and trans-Anethole. LC₅₀ for the 2nd to 4th instar larvae was estimated as 26–27 μL·L^− 1 and 15–19 μL·L^− 1 for the essential oil and trans-Anethole, respectively. As for the essential oil applied on adults, LC(LD)₅₀ was estimated as 9.3 μL mL^− 1 (spray test), 1.9 μL L^− 1 (fumigation test) and 0.6 μg cm^− 2 (tarsal test), and for trans-Anethole as 8.1 μL mL^− 1 (spray test), 2.1 μL L^− 1 (fumigation test) and 0.4 μg cm^− 2 (tarsal test). The time needed to achieve 50% mortality after application of LC(LD)₉₉ of the essential oil was significantly different; for example, in larvicidal assays it ranged from 15 to 235 min depending on the larval instar, and from 9 to 180 min when applied to adults, depending on the mode of application. It was also found that temperature had an important effect on the larvicidal efficacy of the essential oil, and oviposition deterrent activity was studied.The essential oil and trans-Anethole were toxic for Daphnia magna (62–92% mortality) and significantly reduced its fertility at high concentrations (35–50 μL mL^− 1) and long exposure (48 h). However, no negative effect on Daphnia mortality or fertility was found at shorter exposure times (6 h) and/or lower concentrations (20 μL mL^− 1).Based on the results of this study, we can recommend the essential oil from P. anisum as a suitable active substance for potential botanical insecticides.     

Accumulation of phycocyanin in heterotrophic and mixotrophic cultures of the acidophilic red alga Galdieria sulphuraria

The relationship between light intensity, nitrogen availability and pigmentation was investigated in mixotrophic and heterotrophic cultures of the unicellular red alga Galdieria sulphuraria 074G, a potential host for production of the blue pigment, phycocyanin (PC). During the exponential growth phase of batch cultures, G. sulphuraria 074G contained 2–4 mg phycocyanin per g dry weight. In carbon-limited and nitrogen-sufficient batch cultures grown in darkness, this value increased to 8–12 mg g⁻¹ dry weight during the stationary phase, whereas the phycocyanin content in nitrogen-deficient cells decreased to values below 1 mg g⁻¹ dry weight during stationary phase. Light intensities between 0 and 100 μmol photons m⁻² s⁻¹ had no influence on phycocyanin accumulation in mixotrophic cultures grown on glucose or fructose, while light stimulated phycocyanin synthesis in cultures grown on glycerol, in which the phycocyanin content in stationary phase was increased from 10 mg g⁻¹ dry weight in darkness to 20 mg g⁻¹ dry weight at a light intensity of 80 μmol photons m⁻² s⁻¹. At higher light intensities, less phycocyanin accumulated than at lower intensities, irrespective of the carbon substrate used. In carbon-limited continuous flow cultures grown on glucose or glycerol at a dilution rate of 0.63 day⁻¹, corresponding to 50% of the maximum specific growth rate, the highest steady-state phycocyanin content of 15–28 mg g⁻¹ dry weight was found at 65 μmol photons m⁻² s⁻¹. In contrast to the apparent glucose repression of light-induced PC synthesis observed in batch cultures, no glucose repression of the light stimulation was observed in continuous flow cultures because the glucose concentration in the culture supernatant always remained at limiting levels. Despite the fact that G. sulphuraria 074G contains less phycocyanin than some other microalgae and cyanobacteria, the ability of G. sulphuraria 074G to grow and synthesize phycocyanin in heterotrophic or mixotrophic cultures makes it an interesting alternative to the cyanobacterium, Spirulina platensis presently used for synthesis of phycocyanin.     

Selenium accumulation in the floral tissues of two Brassicaceae species and its impact on floral traits and plant performance

Selenium (Se) is a metalloid that can occur naturally in soils from the Cretaceous shale deposits of a prehistoric inland sea in the western United States. Agricultural irrigation and runoff solubilizes Se from these shales, causing buildups of toxic levels of selenate (SeO₄²⁻) in water and soil. Our main objective was to investigate the accumulation of Se in two Brassicaceae species chosen for their potential as phytoremediators of Se contaminated soils. We tested the hypothesis that Se will accumulate in the pollen and nectar of two plant species and negatively affect floral traits and plant reproduction. Certain species of Brassicaceae can accumulate high concentrations of Se in their leaf tissues. In this study Se accumulation in plant tissues was investigated under greenhouse conditions. Se accumulator (Brassica juncea) and Se hyperaccumulator (Stanleya pinnata) plants were irrigated in sand culture with 0 μM selenate (control), 8 μM selenate, and 13 μM selenate.Nectar and pollen in S. pinnata contained up to 150 μg Se mL⁻¹ wet weight and 12900 μg Se g⁻¹ dry weight when irrigated with 8 μM selenate. Se levels in nectar (110 μg Se mL⁻¹ wet weight) and pollen (1700 μg Se g⁻¹ dry weight) were not as high in B. juncea. Floral display width, petal area and seed pod length were significantly reduced in the 13 μM selenate Se treatment in B. juncea. S. pinnata floral traits and seeds were unaffected by the Se treatments.This study provides crucial information about where some of the highest concentrations of Se are found in two phytoremediators, and may shed light on the potential risks pollinators may face when foraging upon these accumulating plants. In the field, duration of the plant's exposure, Se soil and water concentrations as well as other environmental factors may also play important roles in determining how much Se is accumulated into the leaf and floral tissues. Our greenhouse study shed light on two species’ ability to accumulate Se, as well as determined the specific plant tissues where Se concentrations are highest.     

Comparison of two matrices for selective recovery of C595 diabody fragment (dbFv) from Escherichia coli lysates

A comparative study of the performance of two types of adsorbent (Streamline Quartz Base and Upfront Matrices), derivatized with the same affinity ligand (RPAP) to recover C595 diabody fragment (dbFv) from Escherichia coli lysates has been undertaken. Both streamline and Upfront Matrices are characterized by a particle size range of 100–300 μm. Streamline has a density of 1.20 g cm⁻³ and ligand concentration of 0.85 μmol ml⁻¹. Upfront has a density of 1.35 g cm⁻³ and ligand concentration of 0.83 μmol ml⁻¹. The release of C595 dbFv from E. coli cells was achieved by a chemical lysis method. The recovery performance of both adsorbents was evaluated in terms of operational productivity and elution yield of C595 dbFv in packed bed (clarified feedstock) and expanded bed (unclarified and clarified feedstock) chromatography systems. Streamline and Upfront adsorbents exhibited diabody operational productivities of 131 and 202 mg l⁻¹, respectively, with an elution yield of 92 and 94%, respectively, in packed bed operation. Streamline and Upfront adsorbents exhibited diabody operational productivities of 54.5 and 123.7 mg l⁻¹, respectively, with an elution yield of 89 and 92%, respectively, in expanded bed operation.