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At least 1,063 records · Page 59Linked to original sources
PubMed2006

Effect of horticultural waste composting on infected plant residues with pathogenic bacteria and fungi: integrated and localized sanitation.

The aim of this work was to study the effect of composting on the viability of plant pathogenic fungi and bacteria. The research consisted of pilot-scale composting of horticultural waste in compost windrows. Studies were carried out on vegetable residues infected with plant pathogenic microorganisms included by either integrated or localized infection. In the first case, the plant pathogen viability was investigated when infected material was mixed throughout compost, while the localized infection was used to study the effect of the composting process on plant waste spot-inoculated with pathogenic microorganisms. Results for localized sanitation showed the total elimination of all tested phytopathogens between 48 and 120 h after composting began. In this case significant differences were observed in relation to 9 different zones in the pile. The disappearance of these microorganisms was similar when all plant waste included in the windrow was infected (integrated infection). Additionally, the results obtained confirmed that the bacteria showed a greater capacity to persist during composting than the fungi. Composting is therefore considered a useful method for recycling horticultural waste and eliminating phytopathogenic bacteria and fungi that inhabit this kind of residue.

Agriculture↗
PubMed2001

Oxidation of triphenylarsine to triphenylarsineoxide by Trichoderma harzianum and other fungi.

Arsenic resistant strains of bacteria and fungi were isolated from soil contaminated by chemical warfare agents. Until now, no metabolic products of microbial attack against the phenyl residues of the model substrate triphenylarsine (TP) were found if it was incubated together with these strains in liquid culture assays. However, one of the isolated fungi, Trichoderma harzianum As 11, was found to oxidize TP to triphenylarsineoxide (TPO). The yeast Trichosporon mucoides SBUG 801 and the white-rot fungus Phanerochaete chrysosporium were also able to oxidize the As(III) in TP. In addition, P. chrysosporium transformed phenylarsineoxide (PAO) to phenylarsonic acid (PAA) under O2-atmosphere. By means of a respirometer system, the oxidation of TP by T. harzianum As 11 was confirmed by a significantly higher consumption of oxygen in the presence of these compounds. HPLC analysis of the oxidation products TPO and PAA in the medium of the assays provided evidence for the transfer reaction of As(III) to As(V) in organic bonds. The oxidation products TPO and PAA are more hydrophilic than TP and PAO. Therefore, it was concluded that particular fungi contribute to the mobilization of arsenic in soil contaminated by chemical warfare agents.

Arsenicals↗
PubMed2002

Mitosis and motor proteins in the filamentous ascomycete, Nectria haematococca, and some related fungi.

Among filamentous fungi, mitosis has been studied in-depth in just a few species. The mitotic apparatuses in the ascomycetous Fusarium spp. are the most clearly and readily visualized in vivo within this group; fluorescent labeling is unnecessary. This superior cytological tractability has enabled detailed studies and revealing experiments that have led the way toward a more complete understanding of fungal mitosis. Some of the most important discoveries include the role of half-spindles in development of the bipolar spindle, the existence of true kinetochores in fungi, the unorthodox chromosome configurations and movements comprising metaphase and anaphase A, the attachment of astral microtubules to the plasmalemma, the role of the astral pulling force in elongating the spindle, an inwardly directed force within the spindle, and microtubule cross-bridging in both spindle and asters. Recent research has focused on the roles of microtubuleassociated motor proteins in Fusarium solani f. sp. pisi (anamorph of Nectria haematococca). Cytoplasmic dynein was shown to be involved in the development and/or maintenance of mitotic asters and necessary for motility and functionality of the interphase spindle pole body. The inwardly directed force within the anaphase spindle was shown to be produced by a kinesin-related protein, NhKRP1. Because of its superior cytological tractability, the considerable and unique knowledge we have of many aspects of its mitosis, and its genetic tractability, Fusarium solani f. sp. pisi is a good choice for further investigations of mitosis in filamentous fungi.

Ascomycota↗
PubMed2001

Growth, dye degradation and ligninolytic activity studies on Zimbabwean white rot fungi.

White rot fungi were collected from Chirinda and Chimanimani hardwood forests in Zimbabwe and studied with respect to growth temperature optima and dye decolorization. Temperature optima were found to vary (between 25-37 degrees C) amongst the isolates. The isolates were screened for their ability to degrade the polymeric dyes; blue dextran and Poly R478 and the triphenylmethane dyes; cresol red, crystal violet and bromophenol blue. Semi-quantitative determination of the hydrolytic enzyme activities possessed by the white rot fungi was determined using the API ZYM system. Lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase activities in the fungi were also determined. No LiP was detected in any of the isolates but all isolates showed manganese peroxidase and laccase activities. Time related decolorization studies and optimum pH determinations for Poly R478 degradation by the isolates were carried out in liquid cultures. The most significant rates of Poly R478 decolorization in liquid cultures were found with the following isolates: Trametes cingulata, Trametes versicolor, Trametes pocas, DSPM95 (a species to be identified), Datronia concentrica and Pycnoporus sanguineus.

Journal Article↗
PubMed1997

Epigenetic phenomena in filamentous fungi: useful paradigms or repeat-induced confusion?

Epigenetic mechanisms can serve as genome defense systems. In haploid nuclei of special sexual cells of fungi, such as Neurospora and Ascobolus, duplicated genes are silenced by hypermutation, DNA methylation, or both. In some cases, DNA introduced into the genome of Neurospora cells by transformation can also inhibit homologous genes by a silencing mechanism that does not involve DNA pairing or methylation and appears to be post-transcriptional. Transforming DNA can also trigger de novo methylation in vegetative cells, which then causes transcriptional silencing. The rules governing silencing in vegetative cells of fungi are undefined, but repeated sequences seem particularly susceptible to these processes. Thus, fungi exhibit both repeat-induced and repeat-associated silencing mechanisms. Additionally, some native genes depend on homologous pairing in the diplophase for proper regulation. Together, these processes should limit the proliferation of transposable elements and serve to preserve the overall structure of the genome.

Animals↗
PubMed2002

Effect of oil extracted from some medicinal plants on different mycotoxigenic fungi.

Essential oils of 12 medicinal plants were tested for inhibitory activity against Aspergillus flavus, A. parasiticus, A. ochraceus and Fusarium moniliforme. The oils of thyme and cinnamon (< or = 500 ppm), marigold (< or = 2000 ppm), spearmint, basil, quyssum (3000 ppm) completely inhibit all the test fungi. Caraway was inhibitory at 2000 ppm against A. flavus, A. parasiticus and 3000 ppm against A. ochraceaus and F. moniliforme. A. flavus, A. ochraceus, A. parasiticus and F. moniliforme were completely inhibited by anise at< or = 500 ppm. However, chamomile and hazanbul at all concentrations were partially effective against the test toxigenic fungi. The results indicate that the test toxigenic fungi are sensitive to the 12 essential oils, and particularly sensitive to thyme and cinnamon. The results also showed that the essential oils of thyme, cinnamon, anise and spearmint have more effect on fungal development and subsequent mycotoxin production in wheat grains. The extent of inhibition of fungal growth and mycotoxin production was dependent on the concentration of essential oils used.

Antifungal Agents↗
PubMed2003

A Blumeria graminis gene family encoding proteins with a C-terminal variable region with homologues in pathogenic fungi.

In a study aimed at characterising, at the molecular level, the obligate biotrophic fungus Blumeria graminis f. sp. hordei (Bgh), we have identified a novel group of genes, the Egh16H genes, and shown that two of these are up-regulated during primary infection of barley leaves. The genes have partial homology to a previously characterised Bgh gene family, Egh16. Egh16 and Egh16H are subfamilies of a larger multigene family with presently about 15 members identified in Bgh. Egh16H has about ten members, and we show that five of these are expressed as highly conserved mRNAs that are predicted to encode proteins with a C-terminal variable region. Egh16H has high homology to sequences in Magnaporthe grisea and other plant pathogenic fungi, as well as sequences of both the insect pathogen Metarhizium anisopliae and the human pathogen Aspergillus fumigatus. No close homologues of Egh16H were found in the non-pathogenic fungi Neurospora crassa and Aspergillus nidulans. We predict that Egh16H plays a general role in the interaction between pathogenic fungi and their hosts. At present, the large number of gene family members with C-terminal variation appears to be unique for Bgh, and the Egh16/Egh16H gene family is to our knowledge the largest gene family so far characterised in this fungus.

Amino Acid Sequence↗
PubMed2001

Effects of various media and supplements on laccase production by some white rot fungi.

White rot fungi produce three main extracellular enzymes involved in ligninolysis; laccase, lignin peroxidase and manganese peroxidase. Though all white rot fungi do not produce all three enzymes, laccase occupies an important place in ligninolysis. The present paper reports its production by some white rot fungi; Daedalea flavida, Phlebia brevispora, Phlebia radiata and Polyporus sanguineus under different nutritional conditions. Of the various basal media tested, mineral salts malt extract broth proved to be the best medium for laccase production. Sugarcane bagasse proved to be the best laccase inducer among the various supplements added to different media.

Alcohols↗
PubMed2002

The effect of aeration on the biotransformation of lignocellulosic wastes by white-rot fungi.

The mineralisation and the humification of organic matter (OM) in sterile horticultural plant wastes inoculated with Coriolus versicolor or Phanerochaete flavido-alba was investigated under different aeration rates in order to determine their efficacy as potential inoculants for composting. The change in elemental composition, lignin content and OM fractions was analysed during a 90-day incubation. Both fungi degraded 30% of lignin at low aeration rates. Different aeration rates led to significant changes in OM mineralisation induced by C. versicolor, but did not have noticeable effect on P. flavido-alba activity. The mineralisation was more effectively carried out by P. flavido-alba than by C. versicolor. Lignin degradation and the linked humification process were equally achieved by the two fungi and were enhanced in aerated conditions. The fungi analysed may facilitate the composting of lignocellulosic wastes by means of an increase in substrate bioavailability and OM humification.

Air↗
PubMed2002

Polarity in filamentous fungi: establishment, maintenance and new axes.

Germ tube emergence in filamentous fungi appears to be similar to bud emergence in yeast. Several key proteins (e.g. Cdc42, septins, Bni1 formin, Rho1 and Rho3) play common roles in polarity establishment and early polarity maintenance in both processes. Although germ tube extension, which can be thought of as extreme polarity maintenance, uses some of the same genes, they are likely to be regulated differently. Mutations in polarity maintenance genes often lead to a split tip in filamentous fungi, a phenotype without an analogue in yeast. Cell cycle regulation differs between tip splitting and subapical branching, but in both processes filamentous fungi maintain several axes of polar growth simultaneously.

Aspergillus nidulans↗
PubMed2002

Recent studies of protein secretion by filamentous fungi.

Filamentous fungi have been widely exploited for the homologous and heterologous protein production, because of the high capacity of their protein secretion machinery. However, the production of heterologous proteins is often limited while the production of homologous proteins can be very high. Various researches have reported the methods for overcoming this problem and some techniques, such as the fusion gene system, improve the production of heterologous proteins. Recently, the molecular biological study of solid-state culture attracts the attention, because the long history of biological studies has shown that the productivity of protein in the solid-state culture frequently exceeds the productivity of protein in the submerged culture. The recent researches of solid-state culture have revealed the new aspects of protein production in filamentous fungi. Solid-state specific gene expression was observed in the glaB and pepA genes of Aspergillus oryzae. A GC-box and HSE element of the glaB promoter region affected solid-state specific gene expression of this gene. Solid-state culture-specific release of enzymes from the cell wall was also observed in the production of beta-glucosidases in Aspergillus kawachii. Extracellular soluble polysaccharide (ESP) from A. kawachii was concerned with the location of beta-glucosidases. Moreover, ESP and the cell wall fraction of A. kawachii were shown to be involved in the stability of beta-glucosidases. The knowledge of the molecular biology of solid-state culture should provide new approaches for the production of both homologous and heterologous proteins in both submerged culture and solid-state culture of filamentous fungi.

Journal Article↗
PubMed2005

Taking the fungal highway: mobilization of pollutant-degrading bacteria by fungi.

The capacity of fungi to serve as vectors for the dispersion of pollutant-degrading bacteria was analyzed in laboratory model systems mimicking water-saturated (agar surfaces) and unsaturated soil environments (glass-bead-filled columns). Two common soil fungi (Fusarium oxysporum and Rhexocercosporidium sp.) forming hydrophilic and hydrophobic mycelia, respectively, and three polycyclic aromatic hydrocarbon degrading bacteria (Achromobacter sp. SK1, Mycobacterium frederiksbergense LB501TG, and Sphingomonas sp. L138) were selected based on the absence of mutual antagonistic effects. It was shown that fungal hyphae act as vectors for bacterial transport with mobilization strongly depending on the specific microorganisms chosen: The motile strain Achromobacter sp. SK1 was most efficiently spread along hyphae of hydrophilic F. oxysporum in both model systems with transport velocities of up to 1 cm d(-1), whereas no dispersion of the two nonmotile strains was observed in the presence of F. oxysporum. By contrast, none of the bacteria was mobilized along the hydrophobic mycelia of Rhexocercosporidium sp. growing on agar surfaces. In column experiments however, strain SK1 was mobilized by Rhexocercosporidium sp. It is hypothesized that bacteria may move by their intrinsic motilitythrough continuous (physiological) liquid films forming around fungal hyphae. The results of this study suggest that the specific stimulation of indigenous fungi may be a strategy to mobilize pollutant-degrading bacteria leading to their homogenization in polluted soil thereby improving bioremediation.

Agar↗
PubMed2002

Ultralow calcium requirements of fungi facilitate use of calcium regulating agents to suppress host calcium-dependent defenses, synergizing infection by a mycoherbicide.

Infection by many fungi activates a variety of calcium dependent defenses in the hosts, slowing or suppressing the attacker and limiting the efficacy of mycoherbicides. The calcium requirement for fungal growth is so low that it could only be implied based on fungi containing calcium-dependent signaling enzymes. Analytical grade media contain <2 microM calcium, and the addition of specific chelators does not affect fungal growth. Hydrophobic derivatives of the calcium-specific chelator BAPTA designed to traverse plant cuticles were synthesized in order to chelate calcium internally during fungal attack. Some chelators as well as calcium precipitating oxalate and channel blocker verapamil were applied with a weakly mycoherbicidal Colletotrichum coccodes to cotyledons of compatible Abutilon threophrasti. They suppressed calcium dependent callose biosynthesis in the weed and increased virulence but may have affected other calcium-dependent processes that facilitate virulence. The low calcium requirement of fungi, and their high affinity for calcium, allows the application of calcium-regulating agents as synergists for mycoherbicides where the weed uses calcium-dependent defenses.

Calcium↗
PubMed1998

Solid-State Production of Beneficial Fungi on Apple Processing Wastes Using Glucosamine as the Indicator of Growth.

Three Trichoderma species, a Penicillium species, and a Rhizopus species were grown on apple pomace at 25 degrees C through solid-state fermentation. The effects of CaCO(3), water, and nitrogen sources on the growth of selected fungi on apple pomace were investigated. Soluble protein and glucosamine contents of fermented pomace were measured as the parameters of fungal growth. The maximum growth of all fungi was established on apple pomace supplemented with 0.05 g of CaCO(3), 2 mL of water, and 0.05 g of NH(4)NO(3) or 0.3 mL of fish protein hydrolysate per gram of pomace. The optimal water activity of the medium for fungal growth was 0.96 at 25 degrees C. This research has provided a clear indication for using glucosamine as a proper indicator of fungal growth in heterogeneous solid-state systems. It also shows potentials for bioconversion of apple processing wastes by beneficial fungi into valuable bioinoculants that are being targeted for agricultural and environmental applications.

Journal Article↗
PubMed2001

Incidence of seed-borne fungi and aflatoxins in Sudanese lentil seeds.

Thirteen seed samples of lentil (Lens esculenta) were incubated on agar plate and moist filter papers (Moist Chambers) at 28 +/- 2 degrees C for determination of the incidence of seed-borne fungi. Aflatoxins content of the seeds was measured using the bright greenish- yellow fluorescence test (BGYF) and thin-layer chromatography (TLC). Sixty-nine species and seven varieties, which belong to 24 genera of fungi, were isolated from this crop. Of these fungi, 51 species and two varieties are considered new for this crop, whereas seven genera and 13 species are new to the mycoflora of the Sudan. The genus Aspergillus (13 species and 6 varieties) which comprising 44% of the total colony count was the most prevalent genus followed by Rhizopus (2 species, 19%), Penicillium (6 species) and Fusarium (8 species) (12%), Chaetomium (3 species) and Cladosporium (5 species) (6%), where the 18 genera (1-4 species) showed very low level of incidence (19%). Of the possible pathogens of lentil plants, F. oxysporum the main cause of vascular wilt was recovered from seeds of this crop. Thin layer chromatographic analysis of chloroform extracts of 13 seed samples showed that only one samples was naturally contaminated with aflatoxins B1, B2, G1 and G2 (14.3 micrograms/kg).

Aflatoxins↗
PubMed2002

Degradation of keratin substrates by fungi isolated from sewage sludge.

Four fungal species including two dermatophytes and two saprophytes were isolated from sewage sludge samples at Basrah (Iraq) they were tested for their degradative ability towards three types of keratin substrates (human hair, chicken feathers and wool). The rate of keratin degradation was expressed as weight loss over three weeks of incubation using a liquid culture medium. Human hair had the highest degradation rate by colonization of Chrysosporium pannicola and Microsporum gypseum at a rate of 62% and 48% respectively. Chicken feathers were highly degraded by Aspergillus flavus (32%) while wool degradation was highest by C. pannicola (45.5%) and Trichophyton mentagrophytes var. erinacei (38%). There was a significant difference (p < 0.001) in keratin substrate degradation rates by the examined fungi. Keratinase activity was highest for C. pannicola and M. gypseum in the culture medium baited with human hair. Aspergillus flavus revealed the highest activity of this enzyme in cultures amended with chicken feathers while T mentagrophytes var. erinacei showed highest keratinase activity in cultures with wool substrate. The amount of protein released into the culture medium varied among the tested fungi. The medium's alkalinity increased over incubation time from 6.5 to 7.8. Microscopic examination showed maceration of the keratin substrates by the fungi.

Arthrodermataceae↗
PubMed2002

Ecology of dermatophytes and other keratinophilic fungi in swimming pools and polluted and unpolluted streams.

The biodiversity and richness of keratinophilic fungal communities including dermatophytes were assessed in three stream sites and three swimming pools in the Nablus district in Palestine, using hair baiting (HBT) and surface dilution plate (SDP) techniques, over 8- and 6-month periods, respectively. The effect of wastewater effluent and selected ecological factors on these fungi in relation to species diversity and population densities were also considered. Fifty keratinophilic fungal species were recovered from the aquatic habitats studied, of which 42 were recovered from stream sites and 22 from swimming pools. Of these fungi 6 were either dermatophytes (Microsporum gypseum, and Trichophyton mentagrophytes) or dermatophyte related species (Chrysosporium merdarium, Ch. tropicum, Ch. keratinophilum and T. terrestre). The most frequently isolated species in the three pools were Acremonium strictum and Cladosporium cladosporioides, using Sabouraud dextrose agar medium (SDA). The most abundant species were Acr. strictum, and Aspergillus flavus. However, only 4 species were isolated using the SDA medium amended with 5-flurocytosine (5-FC). The most frequent and abundant species in the three stream sites using SDA medium were Geotricum candidum, and Penicillium chrysogenum. The most frequent species in the three sites using the 5-FC medium, was Paecilomyces lilacinus. Using HBT, the most abundant and frequent species in the three stream sites were G. candidum, and Pa. lilacinus, on SDA medium, and Pa. lilacinus, and Gliocladium nigrovirens on the 5-FC medium. The 5-FC medium was more suitable for the isolation of dermatophytes and closely related species than the SDA medium; 6 were recovered on 5-FC, whereas only one on the SDA medium. Variation in the levels of keratinophilic fungal populations from the three stream sites sampled 5 times over an 8-month period, followed comparable fluctuation patterns. Wastewater affected fungal population densities with the highest levels in the un-polluted stream sites, and lowest in the heavily polluted sites. Swimming pools, polluted and un-polluted stream sites were found to be rich in pathogenic and potentially pathogenic fungi.

Arthrodermataceae↗
PubMed2003

A screening method for detecting iron reducing wood-rot fungi.

A plate assay using the Fe(II) selective dye, ferrozine, for detecting wood-rot fungi with Fe(III) reductive abilities, was developed. The assay is fast, simple and, in most cases, more sensitive than the corresponding liquid medium test. The brown rot fungi, Gloeophyllum trabeum and Laetiporeus sulphureus, displayed higher iron reductive capabilities than white rot fungi, Trametes versicolor, Ganoderma australe and Ceriporiopsis subvermispora.

Basidiomycota↗