Spread and partitioning of arsenic in soils from a mine waste site in Madrid province (Spain)

The formation of scorodite is an important mechanism for the natural attenuation of arsenic in a wide range of environments. It is dumped on site by metallurgical industries to minimize arsenic release. However, the long-term stability of these deposits is unclear. Sequential As extractions and synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy were used to determine both As and Fe speciation in a small catchment area affected by a scorodite-rich waste pile at an abandoned smelting factory. Our results indicate that this deposit behaves as an acute point source of As and metal pollution and confirms the strong association of As(V) with Fe(III) oxide phases, highlighting the important role of ferrihydrite as an As scavenger in natural systems. In this seasonally variable system, other trapping forms such as jarosite-like minerals also play a role in the attenuation of As. Overall, our results demonstrate that scorodite should not be considered an environmental stable repository for As attenuation when dumped outside because natural rainfall and the resulting runoff drive As dispersion in the environment and indicate the need to monitor and reclamate As-rich mine deposits.

Detection and characterization of silver nanoparticles and dissolved species of silver in culture medium and cells by AsFlFFF-UV-Vis-ICPMS: application to nanotoxicity tests

A methodology based on Asymmetric Flow Field-Flow Fractionation (AsFlFFF) coupled with UV-Vis absorption spectrometry and ICP mass spectrometry (ICPMS) has been developed and applied to the study of silver nanoparticles (AgNPs) and dissolved species of silver in culture media and cells used in cytotoxicity tests. The effect of a nano-silver based product (protein stabilized silver nanoparticles ca. 15 nm average diameter) on human hepatoma (HepG2) cell viability has been studied. UV-Vis absorption spectrometry provided information about the nature (organic vs. nanoparticle) of the eluted species, whereas the silver was monitored by ICPMS. A shift towards larger hydrodynamic diameters was observed in the AgNPs after a 24 hour incubation period in the culture medium, which suggests a "protein corona" effect. Silver(I) associated with proteins present in the culture medium has also been detected, as a consequence of the oxidation process experimented by the AgNPs. However, the Ag(I) released into the culture medium did not justify the toxicity levels observed. AgNPs associated with the cultured HepG2 cells were also identified by AsFlFFF, after applying a solubilisation process based on the use of tetramethylammonium hydroxide (TMAH) and Triton X-100. These results have been confirmed by transmission electronic microscopy (TEM) analysis of the fractions collected from the AsFlFFF. The effect of AgNPs on HepG2 cells has been compared to that caused by silver(I) as AgNO3 under the same conditions. The determination of the total content of silver in the cells confirms that a much larger mass of silver as AgNPs with respect to AgNO3 (16 to 1) is needed to observe a similar toxicity.

Multielement characterization of metal-humic substances complexation by size exclusion chromatography, asymmetrical flow field-flow fractionation, ultrafiltration and inductively coupled plasma-mass spectrometry detection: a comparative approach

The use of three different separation techniques, ultrafiltration (UF), high performance size exclusion chromatography (HPSEC) and asymmetrical flow field-flow fractionation (AsFlFFF), for the characterization of a compost leachate is described. The possible interaction of about 30 elements with different size fractions of humic substances (HS) has been investigated coupling these separation techniques with UV-vis absorption spectrophotometry and inductively coupled plasma-mass spectrometry (ICP-MS) as detection techniques. The organic matter is constituted by a polydisperse mixture of humic substances ranging from low molecular weights (around 1kDa) to significantly larger entities. Elements can be classified into three main groups with regard to their interaction with HS. The first group is constituted by primarily the monovalent alkaline metal ions and anionic species like B, W, Mo, As existing as oxyanions all being not significantly associated to HS. The second group consists of elements that are at least partly associated to a smaller HS size fraction (such as Ni, Cu, Cr and Co). A third group of mainly tri- and tetravalent metal ions like Al, Fe, the lanthanides, Sn and Th are rather associated to larger-sized HS fractions. The three separation techniques provide a fairly consistent size classification for most of the metal ions, even though slight disagreements were observed. The number-average molecular weight (Mn), the weight-average molecular weight (Mw) and the polydispersity (rho) parameters have been calculated both from AsFlFFF and HPSEC experiments and compared for HS and some metal-HS species. Differences in values can be partly explained by an overloading effect observed in the AsFlFFF experiments induced by electrostatic repulsion effects in the low ionic strength, high pH carrier solution. Size information obtained from ultrafiltration is not as resolved as for the other methods. Molecular weight cut-offs (MWCO) of the individual filter membranes refer to globular proteins and molecular weight information may therefore, deviate from that given by the other methods after calibration with polystyrene sulfonate (PSS) standards.

Reagent injection FIA system for lead determination by hydride generation - quartz-tube atomic absorption spectrometry

A method is proposed for the determination of lead by generation of its hydride and detection by quartz-tube AAS using a reagent injection FIA system based on the injection of sodium tetrahydroborate. Lead hydride generation was carried out using a combination of 0.5 M nitric acid, 10% m/ v hydrogen peroxide and 10% m/ v sodium tetrahydroborate. The characteristic concentration obtained was 3.1 ng mL(-1) and the detection limit was 2.6 ng mL(-1) for an injected volume of 0.125 mL of tetrahydroborate.

The Aspergillus nidulans carnitine carrier encoded by the acuH gene is exclusively located in the mitochondria

The location of the Aspergillus nidulans carnitine/acyl-carnitine carrier (ACUH) was studied. ACUH with a His-tag at its N-terminus was over-expressed in Escherichia coli and purified by Ni(2+) affinity chromatography. The purified protein was utilised to raise polyclonal antibodies which were characterised by Western blotting. For localisation studies A. nidulans T1 strain, that contains the acuH gene under control of the strong promoter alcA(p), was derived. Results obtained demonstrate the exclusively mitochondrial localisation of ACUH and therefore exclude the targeting of the acuH gene product to the peroxisomal membrane.

Development of a homologous transformation system for the opportunistic human pathogen Aspergillus fumigatus based on the sC gene encoding ATP sulfurylase

The development of a homologous transformation system for the opportunistic human pathogenic fungus Aspergillus fumigatus is described. The system is based on the sC gene encoding ATP sulfurylase. Several A. fumigatus sC mutant strains were readily isolated by strong selection for selenate resistance. The coding region plus upstream and downstream regulatory sequences of the A. fumigatus sC gene were cloned by inverse PCR and then sequenced. Sequencing of the sC cDNA revealed the presence of five introns located within the first half of the gene. The A. fumigatus sC gene encodes a protein of 574 amino acids which is highly similar to ATP sulfurylases from the filamentous fungal species Aspergillus nidulans, Aspergillus terreus and Penicillium chrysogenum. By contrast, ATP sulfurylases from the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe lack the C-terminal adenosine-5'-phosphosulfate kinase-like domain present in the filamentous fungal orthologues. A 3.8-kb DNA fragment amplified by PCR and containing the sC gene plus 5' and 3' flanking regions was cloned into pUC19 to give the vector pSCFUM. Transformation of two different sC mutant isolates with the plasmid pSCFUM established the functionality of this new homologous transformation system. Molecular analysis of sC+ transformants showed that up to 44% of transformed clones contained one or more copies of the entire plasmid integrated at the sC locus. This result also demonstrates the utility of the sC marker for targeting specific genetic constructs to the A. fumigatus sC locus, facilitating studies of gene regulation and function.

The catabolite inactivation of Aspergillus nidulans isocitrate lyase occurs by specific autophagy of peroxisomes

In Aspergillus nidulans, activity of the glyoxylate cycle enzyme isocitrate lyase is finely regulated. Isocitrate lyase is induced by growth on C2 compounds and long-chain fatty acids and repressed by glucose. In addition, activity of isocitrate lyase is subject to a second mechanism of catabolite control, glucose-induced inactivation. Here, we demonstrate that the catabolite inactivation of A. nidulans isocitrate lyase, a process that takes place during glucose adaptation of cells grown under gluconeogenic conditions, occurs by proteolysis of the enzyme. Ultrastructural analyses were carried out in order to investigate the cellular processes that govern the catabolite inactivation of this peroxisomal enzyme. Addition of glucose to oleate-induced cells triggered the specific engulfment and sequestration of peroxisomes by the vacuoles. Sequestration of various peroxisomes by a single vacuole was a frequently observed phenomenon. Results obtained by immunoelectron microscopy using antibodies against A. nidulans isocitrate lyase showed that degradation of this peroxisomal enzyme occurred inside the vacuole. In addition, ultrastructural studies demonstrated that microautophagy was the autophagic pathway involved in degradation of redundant peroxisomes during glucose adaptation of oleate-induced cells of A. nidulans.

Studies on the α-L-Arabinofuranosidase Complex from Sclerotinia fructigena in Relation to Brown Rot of Apple

α-L-Arabinofuranosidase (AF) was detected in apple fruitlets experimentally infected by Sclerotinia fructigena. In extracts of such fruitlets, three AF isoenzymes were separated by preparative isoelectric focusing. When the fungus was grown in shake culture with different carbon sources, AF was detected in each culture filtrate and mycelial homogenate. Although fungus growth and total AF varied with the carbon source, the AF isoenzyme pattern was similar in each instance to that obtained when grown on sodium polypectate.

Each of the partially purified AF isoenzymes behaved differently in substrate specificity and inhibitor studies; however, each showed a specificity for α-L-arabino-furanosides. The two extracellular AF isoenzymes released monomeric arabinose when incubated with araban or apple cell walls. External AF III (pI 6·5) was more active on a substrate of apple cell wall material than external AF I (pI 3·0). The latter form of the enzyme was less susceptible to inhibition by either oxidized or unoxidized apple juice. Two isolates of Sclerotinia fructigena with low growth rate in vivo secreted no AF III in vitro.

Localization of α-L-Arabinofuranosidase and Acid Phosphatase in Mycelium of Sclerotinia fructigena

α-L-Arabinofuranosidase (AF) and acid p-nitrophenyl phosphatase (AP) were secreted by Sclerotinia fructigena grown in a liquid pectin/ammonium tartrate medium. ‘Gentle’ mechanical manipulation of mycelium solubilized most of the AF and much of the AP, while brief acid treatment considerably inactivated both enzymes. Both enzymes were present predominantly in a soluble form in homo-genates prepared for subcellular fractionation, but some particulate activity of both was recovered from a sucrose density gradient in a fraction which also contained mitochondria. Azo-dye techniques with appropriate 1-naphthyl derivatives as substrates and p-(acetoxymercuric) aniline diazotate as capturing agent produced similar staining patterns for both enzymes in the light and electron microscopes, but the distribution of β-glycerophosphatase activity as visualized by the Gomori technique was more variable. A proportion of the activity of the enzymes remaining after fixation was located between the plasmalemma and the hyphal wall, in vacuoles in the cytoplasm, and in spherosome-like bodies. Some evidence was obtained for structure-linked latency of both enzymes and for their secretion by a process of reverse pinocytosis.

The acuH gene of Aspergillus nidulans, required for growth on acetate and long-chain fatty acids, encodes a putative homologue of the mammalian carnitine/acylcarnitine carrier

The Aspergillus nidulans acuH gene, required for growth on acetate and long-chain fatty acids, was cloned by complementation of the acuH13 mutation. Northern blotting analysis showed that transcription of the acuH gene occurs in acetate-grown mycelium and at higher levels in oleate-grown mycelium, but not during growth on glucose minimal medium. The acuH gene encodes a protein of 326 amino acids that belongs to the mitochondrial carrier family. The ACUH protein contains three related segments of approximately 100 amino acids in length, each segment comprising two hydrophobic domains that are probably folded into two transmembrane alpha-helices linked by an extensive polar region. Sequence comparisons suggest that the acuH gene of A. nidulans encodes the homologue of the carnitine/acylcarnitine carrier of rat and man. The uncharacterised proteins YOR100C of Saccharomyces cerevisiae, COLT of Drosophila melanogaster, and DIF-1 of Caenorhabditis elegans also seem to be homologues of ACUH. In addition to the motifs present in all members of the mitochondrial carrier family, we propose the highly conserved motif R(A,S)(V,F)PANAA(T,C)F within the sixth hydrophobic domain of these proteins as the characteristic feature of the carnitine carrier subfamily. The proposed function of the ACUH protein is the transport of acetylcarnitine molecules from the cytosol to the mitochondrial matrix, a process required during growth on acetate or on long-chain fatty acids.

Determination of polychlorinated biphenyls in soybean infant formulas by gas chromatography

A method previously developed for the analysis of organohalogenated compounds in dairy products is now validated for polychlorinated biphenyls (PCBs) determination in soybean infant formulas. The results of this study are consistent with those found for PCBs in powdered full-fat milk. The methodology is based on a solid-liquid extraction step enabling a semi-selective extraction of the apolar lipids of the matrix without affecting the efficiency for the recovery of PCBs. Mean recoveries for the spiked coplanar congeners studied were in the 88-114% range, with relative standard deviations (R.S.D.s) lower than 9.8%. The R.S.D.s related to the determination of endogenous PCBs were in the 1.5-10.0% range. The validated methodology was applied to the PCB analysis in different trademarks of soybean infant formulas commercialised in Spain. Toxic tetraequivalents of tetrachlorodibenzo-p-dioxin and daily intake corresponding to each one were calculated and compared with values previously published and with those found in literature for human breast milk in different countries.

Characterization of Aspergillus nidulans peroxisomes by immunoelectron microscopy

In previous work, we have demonstrated that oleate induces a massive proliferation of microbodies (peroxisomes) in Aspergillus nidulans. Although at a lower level, proliferation of peroxisomes also occurs in cells growing under conditions that induce penicillin biosynthesis. Here, microbodies in oleate-grown A. nidulans cells were characterized by using several antibodies that recognize peroxisomal enzymes and peroxins in a broad spectrum of eukaryotic organisms such as yeast, and plant, and mammalian cells. Peroxisomes were immunolabeled by anti-SKL and anti-thiolase antibodies, which suggests that A. nidulans conserves both PTS1 and PTS2 import mechanisms. Isocitrate lyase and malate synthase, the two key enzymes of the glyoxylate cycle, were also localized in these organelles. In contrast to reports of Neurospora crassa, our results demonstrate that A. nidulans contains only one type of microbody (peroxisomes) that carry out the glyoxylate cycle and contain 3-ketoacyl-CoA thiolase and proteins with the C-terminal SKL tripeptide.

Characterization of oleate-nonutilizing mutants of Aspergillus nidulans isolated by the 3-amino-1,2,4-triazole positive selection method

Conidia of Aspergillus nidulans were mutagenized with ultraviolet light and were incubated on a special selective medium containing the catalase inhibitor 3-amino-1,2,4-triazole. From approximately 5 x 10(7) viable UV-irradiated conidia tested, 423 stable mutants resistant to 3-amino-1,2,4-triazole were recovered, of which 40 were unable to grow on minimal medium with oleic acid as the sole carbon source. These oleate-nonutilizing (Ole-) mutants did not grow on medium with carbon sources requiring functional peroxisomes (oleate, butyrate, acetate, or ethanol), but grew well on medium with carbon sources supposedly not requiring such organelles (glucose, glycerol, l-glutamate, or l-proline). The Ole- mutants carried mutations in one of five nuclear genes affecting acetate utilization: acuJ, acuH, acuE, acuL, and perA. The perA21 strain (DL21) carried a mutation in a gene that is not allelic with any of the known acu loci and displayed a phenotype resembling that described in the Pim- (peroxisome import defective) mutants of Hansenula polymorpha. Hyphae of the perA21 mutant contained a few small peroxisomes with the bulk of peroxisomal enzymes remaining in the 20,000 x g supernatant, but produced wild-type levels of penicillin.

Composition and characterization of soyabean and related products

Soyabean contains about 48 to 50% proteins. Among these, storage proteins are predominant. 7S and 11S globulins are two storage proteins that constitute 80% of the total protein content in soyabean. Moreover, there are other less abundant storage proteins such as 2S, 9S, and 15S globulins. In addition to globulins, enzymes, protease inhibitors (Kunitz and Bowman-Birk), lectin, and other complete the soya protein content. Different methods exist to characterize soya proteins. These methods involve (1) an isolation of proteins from soya commercial products and (2) the use of analytical techniques for protein determination. Soya proteins may interact with other soya components such as minerals, phytic acid, ascorbic acid, and fiber. These interactions, which depend on soya processing and treatment, can decrease the bioavailability of minerals and proteins. Swelling, solubility, viscosity, and capacity to form a gel, an emulsion, or a foam are the main functional properties of soyabean. They are responsible for the wide use of soya in industrial processes.

Rapid separation of soybean globulins by reversed-phase high-performance liquid chromatography

A rapid separation of the main soybean proteins (7S and 11S globulins) was carried out by reversed-phase high-performance liquid chromatography. For this purpose, a linear binary gradient acetonitrile--water--0.1% trifluoroacetic acid, at a flow-rate of 1 ml/min and 50 degrees C temperature was designed. Under the experimental conditions of this work, it was possible to separate five peaks corresponding to the globulins from a soybean protein isolate in 9 min. The characterization of soybean proteins was accomplished by analyzing the 7S and 11S purified fractions obtained from a soybean protein isolate. The method was applied to the separation of soybean proteins from commercial foodstuffs: soybean flour, textured soybean and soybean milks.

Purification and properties of beta-galactosidase from Aspergillus nidulans

Beta-Galactosidase from mycelial extract of Aspergillus nidulans has been purified by substrate affinity chromatography and used to obtain anti-beta-galactosidase polyclonal antibodies. A. nidulans growing in lactose as carbon source synthesizes one active form of beta-galactosidase which seems to be a multimeric enzyme of 450 kDa composed of monomers with 120 and 97 kDa. Although the enzyme was not released to the culture medium, some enzymatic activity was detected in a cell-wall extract, thus suggesting that it can be an extracellular enzyme. Beta-Galactosidase of A. nidulans is a very unstable enzyme with an optimum pH value of 7.5 and an optimum temperature of 30 degrees C. It was only active against beta-galactoside substrates like lactose and p-nitrophenyl-beta-D-galactoside (PNPG).

Induction of beta-oxidation enzymes and microbody proliferation in Aspergillus nidulans

Aspergillus nidulans is able to grow on oleic acid as sole carbon source. Characterization of the oleate-induced beta-oxidation pathway showed the presence of the two enzyme activities involved in the first step of this catabolic system: acyl-CoA oxidase and acyl-CoA dehydrogenase. After isopicnic centrifugation in a linear sucrose gradient, microbodies (peroxisomes) housing the beta-oxidation enzymes, isocitrate lyase and catalase were clearly resolved from the mitochondrial fraction, which contained fumarase. Growth on oleic acid was associated with the development of many microbodies that were scattered throughout the cytoplasm of the cells. These microbodies (peroxisomes) were round to elongated, made up 6% of the cytoplasmic volume, and were characterized by the presence of catalase. The beta-oxidation pathway was also induced in acetate-grown cells, although at lower levels; these cells lacked acyl-CoA oxidase activity. Nevertheless, growth on acetate did not cause a massive proliferation of microbodies in A. nidulans.

Study of a hydrocarbon-utilizing and emulsifier-producing Acinetobacter calcoaceticus strain isolated from heating oil

Twenty bacterial strains were isolated from a sample of contaminated heating oil and screened for their ability to use petroleum and several common fuels as the sole source of carbon and energy. One of the isolates, named MM5, was able to grow on petroleum derivatives and brought about an emulsification of those compounds. Gas chromatography studies showed that strain MM5 was able to degrade hydrocarbons of heating oil. MM5 has been tentatively identified as a strain of Acinetobacter calcoaceticus. The fine structure of MM5 was examined by transmission electron microscopy. Incubation in the presence of hydrocarbon substrates resulted in the development of intracellular electron-transparent inclusions. These structures were absent in the non-hydrocarbon cultures studied.

Glucose-induced inactivation of isocitrate lyase in Aspergillus nidulans

The existence of a second mechanism of catabolite control of isocitrate lyase of Aspergillus nidulans, in addition to the carbon catabolite repression phenomenon recently reported was analysed. Isocitrate lyase was rapidly and specifically inactivated by glucose. The inactivation was irreversible at all stages in the presence of cycloheximide, showing that reactivation depends on de novo protein synthesis. In addition, analysis of glucose-induced inactivation of isocitrate lyase in a creAd-30 strain showed that the creA gene is not involved in this process.

[Degradation of oil derivatives by Acinetobacter calcoaceticus MM5]

This paper describes the isolation of microorganisms from polluted heating oil. The growth of one of them has been studied (Acinetobacter calcoaceticus MM5) in several linear and branched hydrocarbons as well as the effect of its growth on commercial diesel oil. Acinetobacter calcoaceticus MM5 is not capable of using glucose as its only source of carbon, and it needs the presence of nitrogen and phosphorus sources to degrade any petroleum by-product.

Purification and molecular properties of an alpha-galactosidase synthesized and secreted by Aspergillus nidulans

alpha-Galactosidases from mycelial extract and culture filtrate of Aspergillus nidulans have been purified to homogeneity and utilised to obtain polyclonal antibodies anti-alpha-galactosidase. The enzymatic characteristics and the cross reactivity of the antibodies suggest that alpha-galactosidases isolated from the two sources were the same enzyme. Thus, A. nidulans synthesized and secreted only one enzymatic form of alpha-galactosidase which is a multimeric enzyme of 370 kDa composed of four monomers of 87 kDa and a pI of 6.3. The optimum temperature of activity was 50 degrees C and the optimum pH 4-5. The enzyme was stable over a wide range of pH but quite unstable to temperature. alpha-Galactosidase of A. nidulans is a very specific enzyme, it is active only on p-nitrophenyl-alpha-D-galactoside (PNPG), melibiose and raffinose. When PNPG was utilised as substrate melibiose, raffinose, galactose and glucose were competitive inhibitors of the activity.

Ultrastructural changes in Cladosporium cucumerinum during pathogenesis

Three ultrastructural patterns, each one associated with a different stage of pathogenesis, were observed in Cladosporium cucumerinum infecting cucumber cytoledons. (i) Fungal prepenetration structures (conidia and germ tubes) contained numberous lipid bodies. Microbodies were abundant and often associated with lipid bodies. Mitochondria were also abundant. (ii) During the invasion stage, no lipid bodies and relatively few microbodies were observed. Mitochondria were abundant, but differed markedly morphologically from those observed in the prepenetration structures. (iii) In the colonizing hyphae, microbodies were the most abundant organelle, lipid bodies were seldom found, and mitochondria were as observed during invasion. These changes in numbers of organelles may be associated with differences in the metabolic activities of the pathogen at various stages of pathogenesis.