1,721,021 research outputs found
Geomycology of vanadium
No full textIn recent years, increasing levels of vanadium in the environment have raised concern over its release from anthropogenic sources, mainly due to hydrocarbon fuel combustion, mining and industrial activities. Vanadium may be essential for some bacteria and fungi, but can have toxicological effects at high concentrations. It is known that several fungal species can bioaccumulate vanadium. In our research, we investigate some relationships between selected fungal species and vanadium in relation to growth responses, bioaccumulation, and mineral transformation. Six species of saprotrophic fungi (Aspergillus terreus, Cladosporium cladosporioides, Clonostachys rosea, Paecilomyces lilacinus, Penicillum citrinum, Rhizopus arrhizus), isolated from soil with high levels of potentially toxic elements, were tested and results revealed a tolerance to vanadium for all the fungi at concentrations up to 6 mM. In other experiments, Aspergillus niger, Aspergillus ustus, Clonostachys rosea, Paecilomyces lilacinus and Paecilomyces javanicus were able to solubilize a vanadium- and lead-containing insoluble apatite (vanadinite). A. niger was able to transform vanadinite to lead oxalate. Vanadium bioaccumulation and mineral biotransformation by fungi might be key factors underlying tolerance to anthropogenic contamination, their possible role in the environmental fate of vanadium, and in land management and bioremediation approaches
Fungi as bioresources for remediation of HCH-contaminated soils: from microbial community-level physiological profile to selective isolation in enrichment
No full textThe interaction between human activities and global change (including persistent chemicals
pollution) poses severe threats for the soil microbiota thus reducing the provision of ecosystem
services1. In this context -, -, and -hexachlorocyclohexane (HCH) are highly persistent organic
pollutants ofglobal concern, and a severe risk for human health and ecosystem functioning.
Soil fungi, thanksto the ability to tolerate, bioaccumulate and biodegrade HCH, are important
bioresources as biobased solutions for HCH-contaminated soil remediation. The study area
was selected within the National Priority Site “Bacino del Fiume Sacco” in the Metropolitan
City of Rome (Italy). Soil cores, up to 1 m of depth, were collected from 2 plots and later
divided in topsoil (TS: 0-10 cm) and subsoil (SS: 10-100 cm) samples. The first goal was to
characterize the microbial community level physiological profile, so the soil samples were
analysed by the Biolog EcoPlateTM Technique2 to compare metabolic activities of the
communities at different depths (TS and SS). Moving on, the project focused on the fungal
fraction of the microbial community, evaluating the fungal loaddifferences between TS and
SS, through the count of the colony forming units (CFUs/dry soil weight). The CFUs results
show a higher fungal load in topsoil than that in subsoil by one order of magnitude. To isolate
fungal bioresources suitable for HCH degradation, a selective enrichment procedure with a high
concentration HCH mixture as the only carbon source, was carried out. At the end of the
procedure several species, mainly belonging to Fusarium and Alternaria genera,were isolated
and are currently preserved in the Culture Collection of the Fungal Biodiversity Laboratory
(FBL) of the Department of Environmental Biology of Sapienza University of Rome. The
isolated fungi represent useful bioresources for further studies aimed at the development of
mycoremediation application for HCH contaminated soil remediation
Fungal biotransformation of vanadinite (Pb5(VO4)3Cl)
No full textBioweathering effects of different saprotrophic fungi on the vanadium- and lead-containing insoluble apatite group mineral, vanadinite (Pb5(VO4)3Cl) were investigated. Despite the insolubility of vanadinite, fungi exerted both biochemical and biophysical effects on the mineral including etching, penetration and formation of new biominerals. Lead oxalate was the main precipitated biomineral by Aspergillus niger during bioleaching of natural and synthetic vanadinite. Some calcium oxalate monohydrate (whewellite) was also formed with natural vanadinite because of the presence of associated ankerite (Ca(Fe2+,Mg)(CO3)2). A. niger also mediated the precipitation of lead oxalate during growth in the presence of lead carbonate, vanadium(V) oxide and ammonium metavanadate. Abiotic tests confirmed the efficacy of oxalic acid in solubilizing vanadinite and precipitating lead as lead oxalate. Geochemical modelling by PHREEQC and Phreeplot confirmed the complexity of vanadium speciation, and the significant effect of oxalate. Oxalate-vanadium complexes markedly reduced the vanadinite stability field, with cationic lead(II) and lead oxalate also occurring. In all treatments and geochemical simulations, no other lead vanadate, or vanadium minerals were detected. This research highlights the importance of oxalate in vanadinite bioweathering. The findings are also relevant to remedial treatments for lead/vanadium contamination, and novel approaches for vanadium recovery
Fungi in action against hexachlorocyclohexane: a focus on biosurfactants from fungal biodiversity
No full textHexachlorocyclohexane (HCH) is a highly persistent organic pollutant of global concern, involving severe
risks for human health and ecosystem functioning. Mycoremediation represents a feasible nature-based
solution for the restoration of soils polluted by HCH thanks to the ability of fungi to tolerate, bioaccumulate
and degrade it. Known for its insecticidal properties of one of its isomers (γ-HCH), it has been used for a long
time in European soils and despite the ban in the Stockholm Convention, high concentrations exceeding the
threshold values have been found in many areas. One of this is the National Priority Site “Bacino del Fiume
Sacco” within the Metropolitan City of Rome that has been selected as study area. Soil cores up to 1m of depth,
divided in topsoil and subsoil samples, were collected from 2 plots. To isolate fungi able to utilize HCH as the
sole C-source, an isolation in enrichment conditions was carried out providing an high concentration of
isomers’ mixture (α-, β-, γ- and δ-HCH). A total of 49 fungal strains was isolated, mostly belonging to
Fusarium and Alternaria genera. To evaluate the ability of these fungi to produce biosurfactants, metabolites
that enhance HCH biodegradability, three tests were carried out: oil emulsification activity test, oil
displacement test and drop collapse assay. The results of the assays showed the ability of some strains to
produce biosurfactants, making them suitable candidates for further investigation
Growth responses to and accumulation of vanadium in agricultural soil fungi
No full textThe aim of this work was to test the growth response of some selected species to toxic metal vanadium, chosen among those isolated from contaminated agricultural soils (organochlorines, potentially toxic elements) in the "Valle Latina" (Lazio, Italy). This area contains high levels of potentially toxic elements due both to human activities and the presence of volcanic rocks (pyroclastic deposits). In particular. vanadium levels exceed the threshold values established by Italian legislation. The soil fungal community was found to be rich in species and we tested the growth responses of six selected species of saprotrophic fungi (Aspergillus terreus, Cladosporium cladosporioides, Clonostachys rosea, Paecilomyces lilacinus, penicillum citrinum, Rhizopus arrhizus). Culture medium (MEA) was amended with ammonium vanadate at concentrations of 1, 2, 3 and 6 mM. Results were based on growth measurements, the tolerance index (TI), scanning electron microscopy (SEM), energy dispersion X-ray microanalysis (EDXA) and the metal concentration in the biomass determined by means of inductively coupled plasma mass spectrometry (ICP-MS). Results revealed a tolerance to vanadium for all the fungi tested at concentrations of up to 6 mM. Tolerance of soil fungi to high natural metal concentrations might be the key factor underlying their tolerance to anthropogenic contamination
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Tolerance to vanadium as a response of agricultural soil fungi in the Valle Latina (Italy): which are the potentialities for mycoremediation?
No full textThe aim of this work was to investigate a soil fungal community of contaminated agricultural soils and to test the growth response of selected species to the toxic metal vanadium. Physico-chemical analysis was performed on contaminated soils that lay under maize and wheat crops in the Valle Latina (southern Lazio, Italy). The Valle Latina is one of the 57 sites of national interest (S.I.N.). It’s a high environmental risk area due to its industrial sites, waste landfills and agricultural activities and the environmental contamination of hexachlorocyclohexane, an anthropogenic pollutant. Moreover, natural background high level of potentially toxic elements due to volcanic rocks (pyroclastic deposits) occurs in this area in which several elements, including vanadium, thallium and beryllium exceed the threshold values established by Italian legislation, as well. The soil community of saprotrophic fungi of contaminated agricultural soils near the Sacco River have been studied. Contrary to expectations, the community was found to be rich in fungal species (150 species in total), although the typical Penicillium and Aspergillus species components were poorly represented. Species, reported to be tolerant/resistant to heavy metals in the literature and potentially useful in bioremediation, were found. The occurrence of these may be taken as a potential bioindicator of environmental pollution. Vanadium, one of the elements which exceed threshold values, was chosen as metal to test fungi tolerance. In the last decades, evidence in increasing of the environmental levels of vanadium, has raised concern over its release into the atmosphere from anthropogenic sources of which hydrocarbon fuel combustion is the most important. Burning of fossil fuels caused about 110000 t V/a to enter the atmosphere globally (Manfred, 2004). Vanadium is essential for several species of green algae, fungi and nitrogen-fixing microorganisms, as well. We selected six species : Aspergillus terreus Tiegh., Cladosporium cladosporioides (Fresen.) G.A. de Vries, Clonostachys rosea (Preuss) Mussat, Paecilomyces lilacinus (Thom) Samson, Penicillum citrinum Sopp and Rhizopus arrhizus Fischer, among isolated species, reported to be tolerant/resistant to heavy metals in the literature, and examined the growth response by inoculating them with malt extract agar amended with ammonium vanadate at concentrations of 1, 2, 3 and 6 mM to simulate potential environmental concentrations. Metal tolerance was assessed in all samples by means of growth measurements, tolerance index, scanning electron microscopy, electron dispersion spectroscopy and biomass metal concentrations. Results revealed that all the fungi tested tolerated 6 mM concentrations, Clonostachys rosea and Rhizopus arrhizus being the most tolerant. Soil fungi tolerance to natural metal occurrence may explain their tolerance to anthropogenic contamination. Therefore results of this research can contribute to enhance knowledge on the potential use of these fungal species for mycoremediation purposes in polluted sites
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