Fungal leaching of nickeliferous laterites

Extraction of nickel by microbial leaching of Greek laterites is feasible by using ofAspergillus andPenicillium. The effectiveness was found to depend on the ability of the microorganism to produce hydroxycarboxylic acids, especially citric acid, as well as other metabolites. The nickel recoveries achieved were as high as 60%, in 48 d, when the ore was leached in the presence of the living fungi, in a sucrose medium, and as high as 70%, in a much shorter time, when the ore was leached by their metabolic products after pH adjustment by means of sulfuric acid. The use of much cheaper, factory grade, Greek beet molasses as a growth medium proved promising, giving the possibility of making the process more attractive in economic terms.     

Fungal rock phosphate solubilization using sugarcane bagasse

The effects of different doses of rock phosphate (RP), sucrose, and (NH₄)₂SO₄ on the solubilization of RP from Araxá and Catal?o (Brazil) by Aspergillus niger, Penicillium canescens, Eupenicillium ludwigii, and Penicillium islandicum were evaluated in a solid-state fermentation (SSF) system with sugarcane bagasse. The factors evaluated were combined following a 2³?+?1 factorial design to determine their optimum concentrations. The fitted response surfaces showed that higher doses of RP promoted higher phosphorus (P) solubilization. The addition of sucrose did not have effects on P solubilization in most treatments due to the presence of soluble sugars in the bagasse. Except for A. niger, all the fungi required high (NH₄)₂SO₄ doses to achieve the highest level of P solubilization. Inversely, addition of (NH₄)₂SO₄ was inhibitory to P solubilization by A. niger. Among the fungi tested, A. niger stood out, showing the highest solubilization capacity and for not requiring sucrose or (NH₄)₂SO₄ supplementation. An additional experiment with A. niger showed that the content of soluble P can be increased by adding higher RP doses in the medium. However, P yield decreases with increasing RP doses. In this experiment, the maximal P yield (approximately 60?%) was achieved with the lower RP dose (3?g?L^?1). Our results show that SSF can be used to obtain a low cost biofertilizer rich in P combining RP, sugarcane bagasse, and A. niger. Moreover, sugarcane bagasse is a suitable substrate for SSF aiming at RP solubilization, since this residue can supply the C and N necessary for the metabolism of A. niger within a range that favors RP solubilization.     

Pregerminative leaching losses from seeds

Summary Leaching losses from seeds of several species were found to vary with incubation temperature, duration of imbibition up to 24 hours, scarification treatment, and flooding of the substrate. A portion of the total amount leached was lost readily to the external medium. The bulk of the total solids leached was adsorbable on charcoal; minerals, ninhydrin-positive substances, and sugars were found also in appreciable concentrations. Stationed in Logan, Utah 84321, at Forestry Sciences Laboratory, maintained in cooperation with Utah State University.     

Selective leaching of zinc from copper-zinc concentrate

Biooxidation of copper-zinc concentrate with the use of consortia of mesophilic and moderately thermophilic acidophilic chemolithotrophic microorganisms was studied. Pyrrhotite, sphalerite, and chalcopyrite were the main sulfide minerals of the concentrate. The possibility in principal of complete selective leaching of zinc from sulfide concentrate coupled with minimal recovery of copper (less than 20%) was demonstrated. Selective leaching of zinc could be caused by galvanic interactions between minerals of the concentrate during the biooxidation. The results can be used as the basis for the development of the technologies for production of grade copper concentrate not containing zinc from sulfide copper-zinc concentrate obtained from refractory ores.     

Fungal remains from the Late Riphean

The paper describes organic remains of one billion years old from the Lakhanda microbiota of the Uchur-Maya Region of southeastern Siberia. The microfossils were discovered on organic sapropelic films. The preserved morphological characters and some developmental stages of the ancient organisms, which are fixed in fossil state, suggest that some of them resembled zygomycetes. Other microfossils under consideration are comparable to reproductive structures of myxomycetes in the type of fusion of spheroid cells and formation of various types of aggregation (sori). Colonies of unicellular microfossils that are arranged in a branching pseudomycelium superficially resemble yeasts. The presence in the same biota of fungal remains belonging to the Myxomycota and Mycota, as well as members of xanthophyte vaucherian algae, indicates that various branches of eukaryotes might have developed in parallel even earlier than the Late Riphean.     

Assessment of phosphorus leaching losses from arable land

Phosphorus (P) losses from soil to water by erosion and surface runoff have been much studied and quantified. However, P losses by leaching have received much less attention, mainly because, until recently, the quantities involved were not considered to be of environmental significance. Furthermore, P leaching losses, unlike P losses from erosion or surface runoff were not believed to be related to rates of P addition, as inorganic fertilizer or manures. Here we report results from a number of field and laboratory experiments, designed to assess the significance of P leaching losses from soil to water. Annual cumulative total P losses in drainage waters from four UK field sites ranged from about 0.03 to 5 kg P ha⁻¹ during 2001–2002. Molybdate reactive P ranged from 45–57%, soluble organic P from 10–13% and particulate P from 29–45% of total P on the two sites (Broadbalk and Woburn) where they could be accurately measured. The proportions of these different P forms were comparable in all treatments, including drainage waters from the unfertilised soils and soils receiving long-term applications of farmyard manure or inorganic fertilizer. In all soils, there was indication of an Olsen- (0.5 M NaHC0₃-, pH 8.5) extractable P concentration, (termed the Change-Point), where P measured in field drainage waters or in laboratory soil extracts of 0.01 M CaCl₂ began to increase linearly as Olsen-P increased. There was also some agreement between drainage water-P or CaCl₂-P and the Olsen-P concentration where the Change-Point occurred. This suggests that CaCl₂-extractable P may provide an approximate indicator of soil P concentrations above which significant quantities of P may be lost by leaching under field conditions. There were positive linear relationships between soil dithionate-extractable Al and soil organic C with the Change-Point: [Change Point = [(0.049)[Al3+] minus (9.2)(% organic C)] accounting for 93% of the variance in the data. If this relationship holds under further testing it could well be a useful predictor of Change-Points in different soils. Phosphate sorption isotherms were used to study the soil P concentrations above which P was at risk of moving from soil to water. They showed that soil solution P concentrations were significantly lower between pH 6.9–7.2 than between pH 7.7–8.1, with implications for P loss from soil to water.     

Fungal Metabolite from Members of the Genus Rhizopus

A fluorescent metabolite present in seven members of the genus Rhizopus was isolated. This compound appeared green before spray treatment and purple after spray treatment with p-anisaldehyde in visible light. Subsequent purification and structural elucidation of the isolated compound yielded 1-[2,6,10,14-tetramethyl-17-carbomethyl heptadecyl]-1-[2,6,10,14-tetramethyl-17-methanoyl heptadecyl]-benzene.     

Fungal egg-parasites of plant-parasitic nematodes from Spanish soils

We have investigated the presence of fungal egg-parasites in Spanish soils with plant endoparasitic nematodes. Nine out of 68 samples (13%) yielded fungal parasites. The most common (seven strains) was Pochonia chlamydosporia var. chlamydosporia (= Verticillium chlamydosporium var. chlamydosporium), but Lecanicillium lecanii (= Verticillium lecanii) and Paecilomyces lilacinus were also found. Most strains were from cyst nematodes (Heterodera avenae or Heterodera schachtii). Biological factors related with the development and performance of these fungi as biocontrol agents were assessed in laboratory tetsts. Germination for most strains was around 90-100%. Higher biomass values were obtained, for most fungal strains, with complete or yeast extract peptone-glucose liquid media. P. lilacinus and L. lecanii showed the highest sporulation rates (1.0 x 10(9); and 1.5 x 10(10); conidia/g mycelium). All strains had optimum growth at 25 degrees C. High temperature (40 degrees C) was lethal to all fungi but low temperature (5 degrees C) allowed growth of L. lecanii. Most strains showed best growth close to pH 7. Several P. chlamydosporia strains produced diffusible pigments close to pH 3. Lack of moisture (aw = 0.887) in growth medium reduced but never arrested fungus growth. Proteolytic activity was, for all strains, the earliest and highest enzymatic activity. Amylolytic and pectinolytic activities showed the lowest values and the latter was undetectable for most strains. Pathogenicity (70-100percnt; egg infection) and severity (35-40 penetrating hyphae/egg) on Meloidogyne javanica were high for most strains tested. Our results show that agricultural soils in Spain contain fungal parasites susceptible to be biocontrol agents for plant-parasitic nematodes.     

Controls on leaching from coniferous forest floor microcosms

Summary Studies were conducted with coniferous forest floor microcosms to examine the potential influence of acid precipitation, temperature changes, and plant uptake upon the chemistry of soil leachate solutions. The experimental design included two temperatures and three different simulated throughfall chemistry treatments. When the acidity of throughfall inputs to the microscosms increased, the forest floors exhibited increased leaching losses of calcium, magensium, potassium, and ammonium. The fact that aluminum losses did not incrase correspondingly suggested that there may be a kinetic lag in the mobilization and leaching of aluminum. When microcosms were exposed to warmer temperatures, percolates showed increased leaching losses of calcium, potassium, ammonium, sulfate, nitrate, and organic anions. Forest floor microcosms exposed to simulated average field conditions behaved very much like field plots under the same environmental conditions; however, there were predictable differences in leaching losses between laboratory and field systems for those ions which are strongly controlled by plant uptake. In general, the exclusion of plant uptake from microcosms resulted in increased leaching of potassium, nitrate, ammonium. and sulfate relative to field plots.     

A mechanism for the leaching of calcium from foliage

Young bean plants (Phaseolus vulgaris) containing root-absorbed ⁴⁵Ca and ⁸⁶Rb were leached to determine the pathway and mechanism of cation loss by leaching. Calcium is leached from the exchangeable calcium fraction within the plant by a process of ion exchange and diffusion involving exchange sites both within the leaf and on the leaf surface. Leaching of cations is primarily a passive process, although some metabolites may be deposited upon leaf surfaces by active processes. The exchange and diffusion explanation is compatible with current theories of ion uptake and translocation and explains the results of numerous experiments on leaching reported in the literature.     

Fungal endophyte assemblages from ethnopharmaceutically important medicinal trees

Endophytic fungi represent an interesting group of microorganisms associated with the healthy tissues of terrestrial plants. They represent a large reservoir of genetic diversity. Fungal endophytes were isolated from the inner bark segments of ethnopharmaceutically important medicinal tree species, namely Terminalia arjuna, Crataeva magna, Azadirachta indica, Holarrhena antidysenterica, Terminalia chebula, and Butea monosperma (11 individual trees), growing in different regions of southern India. Forty-eight fungal species were recovered from 2200 bark segments. Mitosporic fungi represented a major group (61%), with ascomycetes (21%) and sterile mycelia (18%) the next major groups. Species of Fusarium, Pestalotiopsis, Myrothecium, Trichoderma, Verticillium, and Chaetomium were frequently isolated. Exclusive fungal taxa were recovered from five of the six plant species considered for the study of endophytic fungi. Rarefaction indices for species richness indicated the highest expected number of species for bark segments were isolated from T. arjuna and A. indica (20 species each) and from C. magna (18 species).     

Biosorption of Mercury from Industrial Effluent by Fungal Consortia

Mercury is present in different types of industrial effluents that cause environmental pollution. Conventional methods such as precipitation, oxidation/reduction, ion exchange, filtration, membranes, and evaporation are extremely expensive or inefficient for the removal of mercury from diluted solutions. In this context, the biosorption process has recently been shown to be an effective and economical method. The present work describes the mercury biosorption ability of three fungi, i.e., Aspergillus niger, Trichoderma viride, and Humicola insolens. Monocultures of these strains and 10 different combinations were investigated. The consortium of 24-h-old H. insolens and 48-h-old of A. niger and T. viride in equal ratio was found to be compatible. This consortium decreased the residual mercury from 2.02 to 0.001 μ g/L after 7 days of incubation, and caused a significant reduction in chemical oxygen demand (COD) (92.6%) from an initial level of 21 mg/L.     

Fungal secondary metabolism - from biochemistry to genomics

Much of natural product chemistry concerns a group of compounds known as secondary metabolites. These low-molecular-weight metabolites often have potent physiological activities. Digitalis, morphine and quinine are plant secondary metabolites, whereas penicillin, cephalosporin, ergotrate and the statins are equally well known fungal secondary metabolites. Although chemically diverse, all secondary metabolites are produced by a few common biosynthetic pathways, often in conjunction with morphological development. Recent advances in molecular biology, bioinformatics and comparative genomics have revealed that the genes encoding specific fungal secondary metabolites are clustered and often located near telomeres. In this review, we address some important questions, including which evolutionary pressures led to gene clustering, why closely related species produce different profiles of secondary metabolites, and whether fungal genomics will accelerate the discovery of new pharmacologically active natural products.     

Fungal community associated with marine macroalgae from Antarctica

Filamentous fungi and yeasts associated with the marine algae Adenocystis utricularis, Desmarestia anceps, and Palmaria decipiens from Antarctica were studied. A total of 75 fungal isolates, represented by 27 filamentous fungi and 48 yeasts, were isolated from the three algal species and identified by morphological, physiological, and sequence analyses of the internal transcribed spacer region and D1/D2 variable domains of the large-subunit rRNA gene. The filamentous fungi and yeasts obtained were identified as belonging to the genera Geomyces, Antarctomyces, Oidiodendron, Penicillium, Phaeosphaeria, Aureobasidium, Cryptococcus, Leucosporidium, Metschnikowia, and Rhodotorula. The prevalent species were the filamentous fungus Geomyces pannorum and the yeast Metschnikowia australis. Two fungal species isolated in our study, Antarctomyces psychrotrophicus and M. australis, are endemic to Antarctica. This work is the first study of fungi associated with Antarctic marine macroalgae, and contributes to the taxonomy and ecology of the marine fungi living in polar environments. These fungal species may have an important role in the ecosystem and in organic matter recycling.     

Fungal cell wall galactomannan isolated from Apodus deciduus

The alkali-extractable water-soluble polysaccharide (F1SS) isolated from the cell wall of Apodus deciduus has been studied by methylation analysis and NMR spectroscopy, and its structure established as:where n approximately 130+/-10.