Aqueous geochemistry and oxygen isotope compositions of acid mine drainage from the Río Tinto, SW Spain, highlight inconsistencies in current models

The Rio Tinto river in SW Spain is a classic example of acid mine drainage and the focus of an increasing amount of research including environmental geochemistry, extremophile microbiology and Mars-analogue studies. Its 5000-year mining legacy has resulted in a wide range of point inputs including spoil heaps and tunnels draining underground workings. The variety of inputs and importance of the river as a research site make it an ideal location for investigating sulphide oxidation mechanisms at the field scale. Mass balance calculations showed that pyrite oxidation accounts for over 93% of the dissolved sulphate derived from sulphide oxidation in the Rio Tinto point inputs. Oxygen isotopes in water and sulphate were analysed from a variety of drainage sources and displayed delta O-18((SO4-H2O)) values from 3.9 to 13.6 parts per thousand, indicating that different oxidation pathways occurred at different sites within the catchment. The most commonly used approach to interpreting field oxygen isotope data applies water and oxygen fractionation factors derived from laboratory experiments. We demonstrate that this approach cannot explain high delta O-18((SO4-H2O)) values in a manner that is consistent with recent models of pyrite and sulphoxyanion oxidation. In the Rio Tinto, high delta O-18((SO4-H2O)) values (11.2-13.6 parts per thousand) occur in concentrated (Fe = 172-829 mM), low pH (0.88-1.4), ferrous iron (68-91% of total Fe) waters and are most simply explained by a mechanism involving a dissolved sulphite intermediate, sulphite-water oxygen equilibrium exchange and finally sulphite oxidation to sulphate with O-2. In contrast, drainage from large waste blocks of acid volcanic tuff with pyritiferous veins also had low pH (1.7). but had a low delta O-18((SO4-H2O)) value of 4.0 parts per thousand and high concentrations of ferric iron (Fe(III) = 185 mM, total Fe = 186 mM), suggesting a pathway where ferric iron is the primary oxidant, water is the primary source of oxygen in the sulphate and where sulphate is released directly from the pyrite surface. However, problems remain with the sulphite-water oxygen exchange model and recommendations are therefore made for future experiments to refine our understanding of oxygen isotopes in pyrite oxidation. (C) 2009 Elsevier B.V. All rights reserved.

Potassium budgets in grassland systems as affected by nitrogen and drainage

The main inputs, outputs and transfers of potassium (K) in soils and swards under typical south west England conditions were determined during 1999/00 and 2000/01 to establish soil and field gate K budgets under different fertilizer nitrogen (N) (0 and 280 kg ha(-1) yr(-1)) and drainage (undrained and drained) treatments. Plots receiving fertilizer N also received farmyard manure (FYM). Potassium soil budgets ranged, on average for the two years, from -5 (+N, drained) to +9 (no N and undrained) kg K ha(-1) yr(-1) and field gate budgets from +23 (+N, drained) to +89 (+N, undrained). The main inputs and outputs to the soil K budgets were fertilizer application (65%) and plant uptake (93%). Animals had a minor effect on K export but a major impact on K recycling. Nitrogen fertilizer application and drainage increased K uptake by the grass and, with it, the efficiency of K used. It also depleted easily available soil K, which could be associated with smaller K losses by leaching.

Nitrosospira spp. can produce nitrous oxide via a nitrifier denitrification pathway

Nitrous oxide (N2O) emission from soils is a major contributor to the atmospheric loading of this potent greenhouse gas. It is thought that autotrophic ammonia oxidizing bacteria (AOB) are a significant source of soil-derived N2O and a denitrification pathway (i.e. reduction of NO2- to NO and N2O), so-called nitrifier denitrification, has been demonstrated as a N2O production mechanism in Nitrosomonas europaea. It is thought that Nitrosospira spp. are the dominant AOB in soil, but little information is available on their ability to produce N2O or on the existence of a nitrifier denitrification pathway in this lineage. This study aims to characterize N2O production and nitrifier denitrification in seven strains of AOB representative of clusters 0, 2 and 3 in the cultured Nitrosospira lineage. Nitrosomonas europaea ATCC 19718 and ATCC 25978 were analysed for comparison. The aerobically incubated test strains produced significant (P < 0.001) amounts of N2O and total N2O production rates ranged from 2.0 amol cell(-1) h(-1), in Nitrosospira tenuis strain NV12, to 58.0 amol cell(-1) h(-1), in N. europaea ATCC 19718. Nitrosomonas europaea ATCC 19718 was atypical in that it produced four times more N2O than the next highest producing strain. All AOB tested were able to carry out nitrifier denitrification under aerobic conditions, as determined by production of N-15-N2O from applied N-15-NO2-. Up to 13.5% of the N2O produced was derived from the exogenously applied N-15-NO2-. The results suggest that nitrifier denitrification could be a universal trait in the betaproteobacterial AOB and its potential ecological significance is discussed.

The Wheal Jane wetlands model for bioremediation of acid mine drainage

Acid mine drainage (AMD) is a widespread environmental problem associated with both working and abandoned mining operations. As part of an overall strategy to determine a long-term treatment option for AMD, a pilot passive treatment plant was constructed in 1994 at Wheal Jane Mine in Cornwall, UK. The plant consists of three separate systems, each containing aerobic reed beds, anaerobic cell and rock filters, and represents the largest European experimental facility of its kind. The systems only differ by the type of pretreatment utilised to increase the pH of the influent minewater (pH <4): lime dosed (LD), anoxic limestone drain (ALD) and lime free (LF), which receives no form of pretreatment. Historical data (1994-1997) indicate median Fe reduction between 55% and 92%, sulphate removal in the range of 3-38% and removal of target metals (cadmium, copper and zinc) below detection limits, depending on pretreatment and flow rates through the system. A new model to simulate the processes and dynamics of the wetlands systems is described, as well as the application of the model to experimental data collected at the pilot plant. The model is process based, and utilises reaction kinetic approaches based on experimental microbial techniques rather than an equilibrium approach to metal precipitation. The model is dynamic and utilises numerical integration routines to solve a set of differential equations that describe the behaviour of 20 variables over the 17 pilot plant cells on a daily basis. The model outputs at each cell boundary are evaluated and compared with the measured data, and the model is demonstrated to provide a good representation of the complex behaviour of the wetland system for a wide range of variables. (C) 2004 Elsevier B.V/ All rights reserved.

Bioremediation of acid mine drainage: an introduction to the Wheal Jane wetlands project

Acid mine drainage (AMD) is a widespread environmental problem associated with both working and abandoned mining operations. As part of an overall strategy to determine a long-term treatment option for AMD, a pilot passive treatment plant was constructed in 1994 at Wheat Jane Mine in Cornwall, UK. The plant consists of three separate systems; each containing aerobic reed beds, anaerobic cell and rock filters, and represents the largest European experimental facility of its kind. The systems only differ by the type of pre-treatment utilised to increase the pH of the influent minewater (pH<4): lime-dosed (LD), anoxic limestone drain (ALD) and lime free (LF), which receives no form of pre-treatment. The Wheal Jane pilot plant offered a unique facility and a major research project was established to evaluate the pilot plant and study in detail the biological mechanisms and the geochemical and physical processes that control passive treatment systems. The project has led to data, knowledge, models and design criteria for the future design, planning and sustainable management of passive treatment systems. A multidisciplinary team of scientists and managers from the U.K. universities, the Environment Agency and the Mining Industry has been put together to obtain the maximum advantage from the excellent facilities facility at Wheal Jane. (C) 2004 Elseaier B.V All rights reserved.

Syk-Dependent Cytokine Induction by Dectin-1 Reveals a Novel Pattern Recognition Pathway for C Type Lectins

Pattern-recognition receptors (PRRs) detect molecular signatures of microbes and initiate immune responses to infection. Prototypical PRRs such as Toll-like receptors (TLRs) signal via a conserved pathway to induce innate response genes. In contrast, the signaling pathways engaged by other classes of putative PRRs remain ill defined. Here, we demonstrate that the β-glucan receptor Dectin-1, a yeast binding C type lectin known to synergize with TLR2 to induce TNFα and IL-12, can also promote synthesis of IL-2 and IL-10 through phosphorylation of the membrane proximal tyrosine in the cytoplasmic domain and recruitment of Syk kinase. syk−/− dendritic cells (DCs) do not make IL-10 or IL-2 upon yeast stimulation but produce IL-12, indicating that the Dectin-1/Syk and Dectin-1/TLR2 pathways can operate independently. These results identify a novel signaling pathway involved in pattern recognition by C type lectins and suggest a potential role for Syk kinase in regulation of innate immunity.

Rapid acidification and alkylation: Redox analysis of the MHC class I pathway

The technique of rapid acidification and alkylation can be used to characterise the redox status of oxidoreductases, and to determine numbers of free cysteine residues within substrate proteins. We have previously used this method to analyse interacting components of the MHC class I pathway, namely ERp57 and tapasin. Here, we have applied rapid acidification alkylation as a novel approach to analysing the redox status of MHC class I molecules. This analysis of the redox status of the MHC class I molecules HLA-A2 and HLA-B27, which is strongly associated with a group of inflammatory arthritic disorders referred to as Spondyloarthropathies, revealed structural and conformational information. We propose that this assay provides a useful tool in the study of in vivo MHC class I structure. (c) 2008 Elsevier B.V. All rights reserved.

Flavonoids inhibit the platelet TxA(2) signalling pathway and antagonize TxA(2) receptors (TP) in platelets and smooth muscle cells

What is already known about this subject center dot Flavonoids are largely recognized as potential inhibitors of platelet function, through nonspecific mechanisms such as antioxidant activity and/or inhibition of several enzymes and signalling proteins. center dot In addition, we, and few others, have shown that certain antiaggregant flavonoids may behave as specific TXA2 receptor (TP) ligands in platelets. center dot Whether flavonoids interact with TP isoforms in other cell types is not known, and direct evidence that flavonoid-TP interaction inhibits signalling downstream TP has not been shown. What this study adds center dot This study first demonstrates that certain flavonoids behave as ligands for both TP isoforms, not only in platelets, but also in human myometrium and in TP-transfected HEK 293T cells. center dot Differences in the effect of certain flavonoids in platelet signalling, induced by either U46619 or thrombin, suggest that abrogation of downstream TP signalling is related to their specific blockage of the TP, rather than to a nonspecific effect on tyrosine kinases or other signalling proteins. Flavonoids may affect platelet function by several mechanisms, including antagonism of TxA(2) receptors (TP). These TP are present in many tissues and modulate different signalling cascades. We explored whether flavonoids affect platelet TP signalling, and if they bind to TP expressed in other cell types. Platelets were treated with flavonoids, or other selected inhibitors, and then stimulated with U46619. Similar assays were performed in aspirinized platelets activated with thrombin. Effects on calcium release were analysed by fluorometry and changes in whole protein tyrosine phosphorylation and activation of ERK 1/2 by Western blot analysis. The binding of flavonoids to TP in platelets, human myometrium and TP alpha- and TP beta-transfected HEK 293T cells was explored using binding assays and the TP antagonist H-3-SQ29548. Apigenin, genistein, luteolin and quercetin impaired U46619-induced calcium mobilization in a concentration-dependent manner (IC50 10-30 mu M). These flavonoids caused a significant impairment of U46619-induced platelet tyrosine phosphorylation and of ERK 1/2 activation. By contrast, in aspirin-treated platelets all these flavonoids, except quercetin, displayed minor effects on thrombin-induced calcium mobilization, ERK 1/2 and total tyrosine phosphorylation. Finally, apigenin, genistein and luteolin inhibited by > 50% H-3-SQ29548 binding to different cell types. These data further suggest that flavonoids may inhibit platelet function by binding to TP and by subsequent abrogation of downstream signalling. Binding of these compounds to TP occurs in human myometrium and in TP-transfected HEK 293T cells and suggests that antagonism of TP might mediate the effects of flavonoids in different tissues.

Degradation pathway of bisphenol A: Does ipso substitution apply to phenols containing a quaternary alpha-carbon structure in the para position?

The degradation of bisphenol A and nonylphenol involves the unusual rearrangement of stable carboncarbon bonds. Some nonylphenol isomers and bisphenol A possess a quaternary alpha-carbon atom as a common structural feature. The degradation of nonylphenol in Sphingomonas sp. strain TTNP3 occurs via a type II ipso substitution with the presence of a quaternary alpha-carbon as a prerequisite. We report here a new degradation pathway of bisphenol A. Consequent to the hydroxylation at position C-4, according to a type 11 ipso substitution mechanism, the C-C bond between the phenolic moiety and the isopropyl group of bisphenol A is broken. Besides the formation of hydroquinone and 4-(2-hydroxypropan-2-yl) phenol as the main metabolites, further compounds resulting from molecular rearrangements consistent with a carbocationic intermediate were identified. Assays with resting cells or cell extracts of Sphingomonas sp. strain TTNP3 under an 18 02 atmosphere were performed. One atom of 180, was present in hydroquinone, resulting from the monooxygenation of bisphenol A and nonylphenol. The monooxygenase activity was dependent on both NADPH and flavin adenine dinucleotide. Various cytochrome P450 inhibitors had identical inhibition effects on the conversion of both xenobiotics. Using a mutant of Sphingomonas sp. strain TTNP3, which is defective for growth on nonylphenol, we demonstrated that the reaction is catalyzed by the same enzymatic system. In conclusion, the degradation of bisphenol A and nonylphenol is initiated by the same monooxygenase, which may also lead to ipso substitution in other xenobiotics containing phenol with a quaternary a-carbon.

Wnt6 controls amniote neural crest induction through the non-canonical signaling pathway

The neural crest is a multipotent embryonic cell population that arises from neural ectoderm and forms derivatives essential for vertebrate function. Neural crest induction requires an ectodermal signal, thought to be a Writ ligand, but the identity of the Wnt that performs this function in amniotes is unknown. Here, we demonstrate that Wnt6, derived from the ectoderm, is necessary for chick neural crest induction. Crucially, we also show that Wnt6 acts through the non-canonical pathway and not the beta-catenin-dependant pathway. Surprisingly, we found that canonical Wnt signaling inhibited neural crest production in the chick embryo. In light of studies in anamniotes demonstrating that canonical Wnt signaling induces neural crest, these results indicate a significant and novel change in the mechanism of neural crest induction during vertebrate evolution. These data also highlight a key role for noncanonical Wnt signaling in cell type specification from a stem population during development.

Variation in the ability of human influenza A viruses to induce and inhibit the IFN-beta pathway

We investigated the ability of a selection of human influenza A viruses, including recent clinical isolates, to induce IFN-beta production in cultured cell lines. In contrast to the well-characterized laboratory strain A/PR/8/34, several, but not all, recent isolates of H3N2 viruses resulted in moderate IFN-beta stimulation. Through the generation of recombinant viruses, we were able to show that this is not due to a loss of the ability of the NS1 genes to suppress IFN-beta induction; indeed, the NS1 genes behaved similarly with respect to their abilities to block dsRNA signaling. Interestingly, replication of A/Sydney/5/97 virus was less Susceptible to pre-treatment with IFN-alpha than the other viruses. In contrast to the universal effect on dsRNA signaling, we noted differences in the effect of NS1 proteins on expression of interferon stimulated genes and also genes induced by a distinct pathway. The majority of NS1 proteins blocked expression From both IFN-dependent and TNF-dependent promoters by an apparent post-transcriptional mechanism. The NS1 gene of A/PR/8/34 NS1 did not confer these blocks. We noted striking differences in the Cellular localization of different influenza A virus NS1 proteins during infection, which might explain differences in biological activity. (C) 2005 Elsevier Inc. All rights reserved.

Ingestion of onion soup high in quercetin inhibits platelet aggregation and essential components of the collagen-stimulated platelet activation pathway in man: a pilot study

Epidemiological data suggest that those who consume a diet rich in quercetin-containing foods may have a reduced risk of CVD. Furthermore, in vitro and ex vivo studies have observed the inhibition of collagen-induced platelet activation by quercetin. The aim of the present study was to investigate the possible inhibitory effects of quercetin ingestion from a dietary source on collagen-stimulated platelet aggregation and signalling. A double-blind randomised cross-over pilot study was undertaken. Subjects ingested a soup containing either a high or a low amount of quercetin. Plasma quercetin concentrations and platelet aggregation and signalling were assessed after soup ingestion. The high-quercetin soup contained 69 mg total quercetin compared with the low-quercetin soup containing 5 mg total quercetin. Plasma quercetin concentrations were significantly higher after high-quercetin soup ingestion than after low-quercetin soup ingestion and peaked at 2.59 (SEM 0.42) mu mol/l. Collagen-stimulated (0.5 mu g/ml) platelet aggregation was inhibited after ingestion of the high-quercetin soup in a time-dependent manner. Collagen-stimulated tyrosine phosphorylation of a key component of the collagen-signalling pathway via glycoprotein VI, Syk, was significantly inhibited by ingestion of the high-quercetin soup. The inhibition of Syk tyrosine phosphorylation was correlated with the area under the curve for the high-quercetin plasma profile. In conclusion, the ingestion of quercetin from a dietary source of onion soup could inhibit some aspects of collagen-stimulated platelet aggregation and signalling ex vivo. This further substantiates the epidemiological data suggesting that those who preferentially consume high amounts of quercetin-containing foods have a reduced risk of thrombosis and potential CVD risk.

Thiamine is synthesized by a salvage pathway in Rhizobium leguminosarum bv. viciae strain 3841

In the absence of added thiamine, Rhizobium leguminosarum bv. viciae strain 3841 does not grow in liquid medium and forms only "pin" colonies on agar plates, which contrasts with the good growth of Sinorhizobium meliloti 1021, Mesorhizobium loti 303099, and Rhizobium etli CFN42. These last three organisms have thiCOGE genes, which are essential for de novo thiamine synthesis. While R. leguminosarum bv. viciae 3841 lacks thiCOGE, it does have thiMED. Mutation of thiM prevented formation of pin colonies on agar plates lacking added thiamine, suggesting thiamine intermediates are normally present. The putative functions of ThiM, ThiE, and ThiD are 4-methyl-5-(beta-hydroxyethyl) thiazole (THZ) kinase, thiamine phosphate pyrophosphorylase, and 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) kinase, respectively. This suggests that a salvage pathway operates in R. leguminosarum, and addition of HMP and THZ enabled growth at the same rate as that enabled by thiamine in strain 3841 but elicited no growth in the thiM mutant (RU2459). There is a putative thi box sequence immediately upstream of the thiM, and a gfp-mut3.1 fusion to it revealed the presence of a promoter that is strongly repressed by thiamine. Using fluorescent microscopy and quantitative reverse transcription-PCR, it was shown that thiM is expressed in the rhizosphere of vetch and pea plants, indicating limitation for thiamine. Pea plants infected by RU2459 were not impaired in nodulation or nitrogen fixation. However, colonization of the pea rhizosphere by the thiM mutant was impaired relative to that of the wild type. Overall, the results show that a thiamine salvage pathway operates to enable growth of Rhizobium leguminosarum in the rhizosphere, allowing its survival when thiamine is limiting.

PtdIns(5)P activates the host cell PI3-kinase/Akt pathway during Shigella flexneri infection

The virulence factor IpgD, delivered into nonphagocytic cells by the type III secretion system of the pathogen Shigella flexneri, is a phosphoinositide 4-phosphatase generating phosphatidylinositol 5 monophosphate (PtdIns(5) P). We show that PtdIns(5) P is rapidly produced and concentrated at the entry foci of the bacteria, where it colocalises with phosphorylated Akt during the first steps of infection. Moreover, S. flexneri-induced phosphorylation of host cell Akt and its targets specifically requires IpgD. Ectopic expression of IpgD in various cell types, but not of its inactive mutant, or addition of short-chain penetrating PtdIns(5) P is sufficient to induce Akt phosphorylation. Conversely, sequestration of PtdIns(5) P or reduction of its level strongly decreases Akt phosphorylation in infected cells or in IpgD-expressing cells. Accordingly, IpgD and PtdIns(5) P production specifically activates a class IA PI 3-kinase via a mechanism involving tyrosine phosphorylations. Thus, S. flexneri parasitism is shedding light onto a new mechanism of PI 3-kinase/Akt activation via PtdIns(5) P production that plays an important role in host cell responses such as survival.