bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved gene expression inAspergillus nidulans
Authors: Hintz William E. , Kalsner Inge , Plawinski Ewa , Guo Zimin , Lagosky Peter A.
Published: May 2008

A variety of gene expression systems have been developed that utilize the promoter and transcriptional regulatory sequences derived from carbon-catabolite repressed genes for the expression of heterologous genes. The alcA expression system of Aspergillus nidulans utilizes the promoter and regulatory sequences derived from the alcohol dehydrogenase I (alcA) gene. Expression of the alcA gene is repressed by a DNA-binding protein (CreA) in the presence of glucose and induced by ethanol under glucose-depleted conditions. One problem encountered during the expression of therapeutic proteins in A. nidulans is the coexpression of secreted proteases at the time of maximal secretion of heterologous product. To avoid the proteases we created an alcA promoter variant that is no longer sensitive to glucose repression hence could drive expression at earlier time points during the fermentation. The use of this promoter variant in the expression of recombinant interleukin-6 is discussed. A second problem encountered during the expression of high-quality human therapeutic proteins in Aspergillus is aberrant glycosylation. Lower eukaryotic systems, such as Aspergillus, tend to add highly branched mannosidic chains to heterologous secreted protein products. N-Glycans can be important for both the structure and function of specific glycoproteins, hence efforts are being made to in vivo alter the type and complexity of N-glycans substituted by A. nidulans. Key words: Aspergillus, gene expression, alcohol dehydrogenase, glycosylation.
Discovery of novel secondary metabolites from fungi—is it really a random walk through a random forest?
Authors: Monaghan Richard L. , Polishook Jon D. , Pecore Victor J. , Bills Gerald F. , Nallin-Omstead Mary , Streicher Stanley L.
Published: May 2008

Twenty-nine Nodulisporium strains isolated from material obtained worldwide were found to produce secondary metabolites as measured by HPLC. Analysis of incubation conditions resulted in the clustering of three solid fermentation conditions and the clustering of five liquid fermentation conditions. Coverage of 69% of the products produced under eight fermentation conditions could be accomplished if one medium from each cluster was used. Subdivision of the Nodulisporium strains into groups based upon morphological similarity allows for a minimization of the rediscovery of common metabolites. Rare metabolites (HPLC peaks) appeared to occur as random events. However, within the set of cultures that produced the mean or greater than the mean number of metabolites, were found all of the producers of rarer metabolites. Key words: Nodulisporium, fermentation screening, endophytes.
The antifungal strobilurins and their possible ecological role
Authors: Anke T.
Published: May 2008

The strobilurins and the closely related oudemansins are new respiration inhibitors, binding to the Qp centre of cytochrome b. Their high antifungal activity against phytopathogenic fungi and their low toxicity towards mammals make them attractive lead compounds for the synthesis of agricultural fungicides. The strobilurins have been isolated from a great number of Basidiomycetes belonging to the genera Strobilurus, Oudemansiella, Xerula, Hydropus, Mycena, Filoboletus, Crepidotus, and Cyphellopsis as well as one Ascomycete, Bolinea lutea. Strobilurin-producing species occur in Europe, the Americas, Africa, and Australia. Most of the producing fungi grow on wood. Since under sterile conditions strobilurin production could be detected in the natural substrate it appears that the strobilurins play a role in securing nutrient resources for the producers from competing fungi. Key words: strobilurins, oudemansins, antibiotics, antifungal, Basidiomycetes.
Collection, characterization, and utilization of germ plasm of Lentinula edodes
Authors: Chang S. T. , Kwan H. S. , Kang Y. N.
Published: May 2008

Wild and cultivated strains of Lentinula edodes have been collected to form a germ-plasm bank of the mushroom. In addition to the ecological, morphological, and physical properties, the strains were characterized to determine their mating types (alleles of A and B incompatibility factors), substrate degradation abilities, mycelial growth rates, and fruiting abilities. The strains were used to establish molecular genetic methods of strain authentification. The genomic fingerprinting method of arbitrarily primed polymerase chain reaction was found to be a better method than the rDNA internal transcribed spacer regions sequence comparison for L. edodes strain typing. The utilization of the characterized germ-plasm bank for the selection of desirable germ plasm for breeding and cultivation is described. The value and use of molecular markers and genetic maps is also discussed. Key words: mating types, mycelial growth rate, molecular markers.
Genetics and systematics of North American populations ofMorchella
Authors: Gessner Robert V.
Published: May 2008

Our knowledge of the genetics and systematics of the genus Morchella in North America has increased greatly because of many recent field and laboratory studies. Field studies have expanded distribution records and provided insights on ascoma development. More detailed morphological studies have improved species descriptions and simplified species identification. Mating studies between monosporous strains and the formation of presumptive heterokaryons have given evidence for species delimitation. The isolation of chemical products and antigen comparisons using ELISA have provided additional support for species concepts. Electrophoretic studies of allelic variation have given insights into the genetic structure of morels from different geographical areas. Sequence data from the nuclear large rDNA (28S) have been used to infer phylogenetic relationships among species. Additional insights have been obtained from physiological and environmental studies on sclerotium formation that have enabled the production of ascoma in culture. This has led to the filing of patents, commercial production, and the availability of growing kits. Key words: Morchella, systematics, genetics, North America, review.
Degradation of the lignocellulose complex in wood
Authors: Blanchette Robert A.
Published: May 2008

Degradation of the lignocellulose complex in wood varies depending on the microorganism causing decay. The degradative processes of white-, brown-, and soft-rot fungi as well as different forms of bacterial degradation are presented. Ultrastructural methods were used to elucidate cell-wall alterations that occurred during the various stages of decay. In wood inoculated with the white-rot fungus Ceriporiopsis subvermispora, changes in the cell wall, such as electron-dense zones after staining with uranyl acetate, were evident during incipient stages of decay. The ratio of syringyl:guaiacyl lignin of different woods, different cell types, and even the different layers within a cell wall influenced the type and extent of decay by white-rot fungi. Soft rots caused unique changes in the lignocellulose matrix. The type of wood substrate governed the form (type I or type II) of soft rot that occurred. Brown-rot fungi depolymerized cellulose early in the decay process and degraded cellulose without prior removal of lignin. Bacterial degradation was common in waterlogged woods and three forms, tunneling, erosion and cavitation, are discussed. In addition to an improved understanding of decay processes in living trees and forest products, knowledge of decomposition mechanisms is important to utilize effectively these microorganisms for new industrial bioprocessing technologies. Key words: biodegradation, white rot, brown rot, soft rot, bacterial degradation.
Transformation of chrysene and other polycyclic aromatic hydrocarbon mixtures by the fungusCunninghamella elegans
Authors: Pothuluri Jairaj V. , Selby Allison , Evans Frederick E. , Freeman James P. , Cerniglia Carl E.
Published: May 2008

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and persistent environmental pollutants; some are mutagenic, toxic, and carcinogenic and remain a public health concern. We investigated the metabolism of mixtures of PAHs and a tetracyclic aromatic hydrocarbon, chrysene, by the filamentous fungus, Cunninghamella elegans ATCC 36112. Cunninghamella elegans metabolized a mixture of PAHs including the carcinogen benzo[a]pyrene, phenanthrene, fluoranthene, pyrene, and acenaphthene completely to hydroxylated intermediates within 24 h. The metabolites from the PAH mixtures were similar to those formed in earlier studies of individual PAH compounds. In separate experiments with chrysene, C. elegans metabolized about 45% of the [5,6,11,12-14C]chrysene added to cultures during 144 h incubation. The two major metabolites of chrysene were separated by reverse-phase high performance liquid chromatography and identified by ultraviolet–visible, mass spectral, and1H-nuclear magnetic resonance techniques as sulfate conjugates of 2,8-dihydroxychrysene and 2-hydroxychrysene. The two major metabolites accounted for about 33% of the total metabolism. The formation of sulfate conjugates of phenolic chrysene metabolites and glucoside conjugates and hydroxylated products of PAH mixtures by C. elegans may be a detoxification step, because these types of products are generally less toxic than the parent compound. Key words: polycyclic aromatic hydrocarbons, PAH mixtures, chrysene, Cunninghamella elegans, biotransformation, oxidation.
Generation of β-glucan elicitors by plant enzymes and inhibition of the enzymes by a fungal protein
Authors: Ham Kyung-Sik , Albersheim Peter , Darvill Alan G.
Published: May 2008

The biosynthesis and accumulation of phytoalexins is a well-studied plant defense response. Plants synthesize and accumulate phytoalexins in response to microbial infection or elicitor treatment. The β-glucan heptaglucoside is a well-studied phytoalexin elicitor isolated from partial acid hydrolysates of Phytophthora sojae f.sp. glycines (Psg) mycelial walls. Using the soybean – Psg system, we have demonstrated that endo-1,3-β-glucanases (EC 3.2.1.39) are the principal soybean enzymes involved in generating phytoalexin oligoglucoside elicitors from mycelial walls. We have also recently observed that Psg secretes a protein that inhibits the soybean endo-1,3-β-glucanase activity that could release elicitors from fungal mycelial walls. This inhibitor protein, which has been purified to homogeneity, does not inhibit endo-1,3-β-glucanases of the fungus or a tobacco pathogenesis-related endo-1,3-β-glucanase. The existence of the inhibitor protein in Psg suggests that pathogens have evolved specific proteins to inhibit the fungal wall-degrading enzymes of their host plants, just as plants have evolved proteins (e.g., pectic enzyme inhibitors) to inhibit plant cell wall degrading enzymes secreted by their pathogens. It seems possible that pathogens secrete inhibitors of other pathogenesis-related proteins (e.g., chitinases) and that the interplay of hydrolases and their inhibitors could determine the outcome of plant – pathogen interactions. Key words: oligosaccharin, phytoalexin, endo-1,3-β-glucanase, glucanase inhibitor protein, elicitor.
The role of cuticle-degrading proteases in fungal pathogenesis of insects
Authors: St. Leger Raymond J.
Published: May 2008

The proteinaceous outer integument of insects forms an effective barrier against most microbes. Only the 700 known species of entomopathogenic fungi effect entry into their hosts by breaching the cuticle. There is accumulating evidence that the ability of fungi to degrade protein may aid their invasion of and growth in this orderly complex structure. Evidence for the particular importance of proteinases derives largely from studies of their production in infected cuticles associated with cuticle degradation, the effects of proteinase inhibitors on pathogen behavior, and by the analysis of protease-deficient mutants. More recently, studies have included the cloning, identification, and manipulation of specific protease genes of Metarhizium anisopliae, particularly those of the subtilisin (chymoelastase) type (designated Pr1) also produced by many other entomopathogenic fungi. Following solubilization of cuticle proteins by Pr1-type endoproteases, complete degradation of the cuticle involves a number of interacting enzyme species including a family of trypsin-like proteinases, metalloproteinases, several aminopeptidases, and a carboxypeptidase. Testing genetically engineered M. anisopliae null mutants of Pr1 indicated that the other endopeptidases can partially substitute for Pr1. The exopeptidases further degrade peptides released by the endopeptidases producing free amino acids for uptake and metabolism. Utilization of these enzymes has assisted investigators in understanding cuticle structure and how the cuticle is degraded naturally, and could lead to improved strain selection of entomopathogenic fungi or the introduction of their genes into other microbes and plants for the purpose of insect control. Key words: proteinaceous insect cuticle, pathogen endopeptidases, exopeptidases, multiple isozymes, enzyme regulation.
Adhesin - receptor interactions in the attachment ofCandida albicansto host epithelial cells
Authors: Douglas L. Julia
Published: May 2008

The ability of Candida albicans to adhere to a variety of host surfaces is thought to be an important factor in the pathogenesis of candidosis. Adhesion of the yeast form of the fungus to epithelial cells can involve several kinds of adhesion – receptor interaction. Yeast adhesins are typically mannoproteins associated with fibrils or fimbriae on the fungal surface. Lectinlike interactions have been identified between the protein portion of two mannoprotein adhesins and glycosides containing L-fucose or N-acetylglucosamine. The fucoside-binding adhesin has been purified and shown to have an affinity for glycosphingolipid receptors carrying the H blood-group antigen. A fimbrial adhesin has also been described that binds to gangliosides containing a βGalNAc(1–4)βGal disaccharide sequence. Other mannoprotein adhesins proposed recently include the factor 6 epitope present on serotype A strains of C. albicans and an integrin analogue. Adhesin expression appears to be regulated by a number of environmental signals, including osmolarity and the availability of iron and sugars. Additional adhesion-dependent signals might trigger further responses such as the initiation of morphogenesis. Key words: Candida albicans, yeast adhesion, epithelial cell adhesion.
Host signals in fungal gene expression involved in penetration into the host
Authors: Kolattukudy Pappachan E. , Li Daoxin , Hwang Cheng-Shine , Flaishman Moshe A.
Published: May 2008

Fungal spores, on contact with their hosts, perceive the plant signals and consequently initiate gene expression that enables the fungus to penetrate through the host barriers. Germination and appressorium formation by Colletotrichum gloeosporioides spore is induced by host surface wax on the growing avocado (Persea americana) fruits and, at ripening of the fruit, ethylene induces multiple appressorium formation. Both the wax and ethylene may use phosphorylation of 29- and 43-kDa proteins in the signal transduction. Unique genes that are expressed during appressorium formation induced by the host signal were cloned and sequenced. These include cap3 and cap5 that encode cysteine-rich small proteins, cap22 that encodes a secreted glycoprotein found in the appressorial wall, and cap20 whose disruption drastically decreases virulence. Disruption of cutinase gene drastically reduces the virulence of Fusarium solani pisi on pea (Pisum sativum L.). The promoter elements in cutinase gene involved in the induction of this gene by the hydroxy fatty acid monomers of cutin were identified and transcription factors that bind these elements were cloned. One of them, that binds to a palindrome, essential for cutinase induction, was found to be phosphorylated. Several proteins kinases from F. solani pisi were cloned. Key words: appressorium, cutin, cutinase, ethylene, gene disruption, protein phosphorylation, protein kinase, transcription factor.
Immunogenic and immunomodulatory properties of mannoproteins from Candida albicans
Authors: Cassone Antonio
Published: May 2008

Candida albicans is a human commensal and opportunistic fungal organism that expresses on its surface and releases into the external milieu a variety of mannoprotein molecules that are relevant in many aspects of host–Candida relationship. We have attempted to relate mannoprotein constituents to the microbial function and (or) host response. For instance, we have recently found that a protein moiety of a 65-kDa mannoprotein is a major target of cell-mediated immune response. The pattern of cytokines produced by mannoprotein-stimulated human mononuclear cell cultures and mannoprotein-specific T cell lines demonstrated abundant interferon-γ and interleukin-2 production with very low or no production of interleukin-4 and interleukin-10, which suggests that MP-65 is recognized by CD4+ cells of T helper 1 subset. A similar cytokine pattern was seen in splenocyte cultures of mice chronically infected with a low-virulence Candida strain (CA-2) and then stimulated in vitro with MP-65-containing mannoprotein fractions, or also in mice immunized with these fractions. On the other hand, the mannan moieties of mannoproteins bear major B cell epitopes that are responsible for serological specificity, and the ordinary antibody response mounted during normal host colonization. Indirect evidence for the importance of this response for the host–Candida relationship is the dramatic modulation of mannan epitopes on the cell surface during growth and morphological development in vivo. One such epitope is a phosphorylated β-1,2-oligomannoside recognized by the monoclonal antibody AF1, which is present on the surface of infecting yeast cells but then lost during an experimental vaginal infection. Finally, mannan moieties also exert powerful activation of the antimicrobial activity of polymorphonuclear cells and release of a variety of pro-inflammatory and immunomodulatory cytokines, in particular interleukin-1β and tumor necrosis factor-α. Overall, these studies emphasize the need for further definition of individual mannoprotein constituents to dissect the multiple biological actions of these highly complex, multifunctional molecular within C. albicans. Key words: mannoproteins, Candida albicans, immunogenicity, immunomodulation.
Spatiotemporal patterns in ectomycorrhizal populations
Authors: Dahlberg Anders , Stenlid Jan
Published: May 2008

To understand the functioning and ecological roles of ectomycorrhizal fungi in natural ecosystems, it is necessary to have adequate knowledge of the spatial distribution of individual mycelial systems in populations and communities and how this distribution may persist or vary with time. However, this issue has attracted relatively little attention until recently. Moreover, the limited information available is mostly based on the distribution of sporocarps, which is at best an unreliable indicator of the location and activity of mycelia. More useful information can be obtained using somatic and sexual incompatibility tests, as well as molecular markers to trace the distribution of individual genets over a range of spatial and temporal scales. For example, it has been possible using this approach to demonstrate that while young populations tend to consist of numerous small mycelia, individuals in older populations tend to be fewer and larger but heterogeneous in scale. It has also been possible to verify the persistence over several years of mycorrhizal mycelial individuals. Such findings represent only the first step in the study of the spatiotemporal dynamics of ectomycorrhizal fungi, which promises to be a rich and important field for future research. Concepts concerning the process and mechanisms likely to affect distribution patterns are discussed. Key words: ectomycorrhiza, population structure, population dynamics, spatiotemporal patterns.
The clonal dynamic in wild and agricultural plant–pathogen populations
Authors: Kohn L. M.
Published: May 2008

The stability or change in clone frequencies during the disease cycle and from year to year is what I term the clonal dynamic. Among pathogenic fungi, the prevalence of efficient asexual reproduction affords the opportunity for invasive, epidemic, clonal colonization and spread. Clonality is probably most extreme in monoculture, although it could be expected to be important in wild plants and in transfers of adaptive pathogenic genotypes between wild and cultivated plants. The clonal dynamic was studied in Sclerotinia sclerotiorum in two experiments, one on four Canadian field populations of cultivated canola and the other on two Norwegian populations of a wild perennial plant, Ranunculus ficaria. Additional samples were made from canola and other crops in Canada and Norway. Four major differences between the agricultural and wild populations were observed. First, in agricultural populations, DNA fingerprint (multilocus haplotype) and mycelial compatibility group were coupled; all individual members of a clone shared a unique fingerprint and all were mycelially compatible. In wild populations, DNA fingerprint and mycelial compatibility group were decoupled. Second, in agricultural populations fingerprint diversity was high, with 594 genotypes recovered from 2747 isolates, but frequently sampled clones were recovered from a wide geographical area repeatedly over a 3-year period; in wild populations fingerprint diversity was low, with 7 genotypes from 300 isolates, and highly localized. Third, in agricultural populations, no evidence of outcrossing and segregation was observed; in the wild populations, some sibling ascospores showed different mycelial compatibility reactions, indicating that crossing had occurred. Last, in agricultural populations, clones were randomly dispersed spatially, probably the result of immigration and mixing of inoculum in air; in the apparently isolated wild populations, strong spatial substructuring was indicated by the distribution of fingerprints, apparently the result of highly localized inbreeding. Clonality was therefore clearly detected in the cultivated plant populations but was difficult to distinguish from inbreeding in the wild populations. Key words: multilocus haplotype, clonality, asexual reproduction, population genetics.
Theoretical and empirical studies of metapopulations: population and genetic dynamics of the Silene–Ustilago system
Authors: Thrall Peter H. , Antonovics Janis
Published: May 2008

Host–pathogen population dynamics may often only be understood by a multifaceted approach designed to understand processes at a regional as well as local scale. We have investigated the regional population dynamics of the anther-smut Ustilago violacea, a pollinator-transmitted fungal disease, and its plant host Silene alba, using descriptive, experimental, and theoretical approaches. A 7-year survey of multiple natural populations revealed persistence of host and pathogen despite a high rate of population turnover. In an experimental metapopulation, disease spread was greater and more rapid in populations that were relatively isolated or had a previous history of disease occurrence. A computer simulation showed that spatial substructuring can drastically alter expectations based on analytical results from single population models of host–pathogen systems. Moreover, the simulation reproduced many of the patterns detected in the long-term survey and predicted that healthy populations should be more resistant than diseased ones, as found experimentally. Key words: metapopulations, host–pathogen dynamics, spatial models, anther-smut diseases.
The chemistry of fungal antagonism and defense
Authors: Gloer James B.
Published: May 2008

Mechanisms of fungal antagonism and defense often include the production of biologically active metabolites by one species that exert effects on potential competitors and (or) predators. Studies carried out in our laboratory and others clearly indicate that such ecological phenomena can serve as valuable leads to the discovery of novel and potentially useful bioactive fungal metabolites. There is evidence that some of these compounds may render advantages to the producing organism, although careful and definitive ecological studies are required to determine this. Nevertheless, the results summarized here demonstrate the broad array of possible benefits that can arise from interdisciplinary studies in this area. This paper focuses primarily on our own investigations of the chemistry involved in fungal antagonism and defense using coprophilous and sclerotial fungi as model systems. These results have potential implications in many areas of study, including fungal ecology, secondary metabolism, chemotaxonomy, organic chemistry, structure determination, antifungal chemotherapy, and insect control. Key words: fungi, antifungal, insecticide, antagonism, chemical defense, secondary metabolites.
Mutualism and antagonism in the mycorrhizal symbiosis, with special reference to impacts on plant community structure
Authors: Francis R. , Read D. J.
Published: May 2008

Examination of the roots of land plants has revealed the occurrence of mycorrhiza in the majority of species, over 70% of which are hosts to zygomycetous fungi that form vesicular–arbuscular (VA) associations. On the basis of experiments with a small number of host species showing enhancement of growth following colonization, it is widely assumed that wherever mycorrhizas are observed, the symbiosis is of the mutualistic type. The value of definitions based on structural rather than functional attributes is here brought into question by experiments simulating the ecologically realistic circumstance in which seeds germinate in soil in the presence or absence of established VA mycelium. These reveal a spectrum of fungal impacts in which some species respond mutualistically, while others, putative hosts or nonhosts, are antagonised, showing reduction of yield and survivorship and, hence, a loss of fitness relative to plants grown without VA fungi. Antagonised species normally grow in disturbed, open habitats and fail to establish in closed communities. It is hypothesised that their turf incompatibility arises from a sensitivity to interference by VA fungi, which consigns them to ruderal habitats. Mycorrhizal fungi, thus, play a role in defining the ecological niches occupied by plants and in determining of plant community composition. Key words: mycorrhiza, vesicular–arbuscular, mutualism, symbiosis, antagonism, plant community.
Effects of industrial pollutants on ectomycorrhizal relationships in temperate forests
Authors: Fellner Rostislav , Pešková Vitězslava
Published: May 2008

A conspicuous decline of macromycetes, especially in ectomycorrhizal species, has been described in the last decade in various parts of temperate Europe. It has been argued that changes in population of these fungi can be attributed to direct or indirect effects of air pollution. In view of the fact that in central Europe these changes preceded a visual damaging of forest or even its decline, it seems that many ectomycorrhizal fungi are very suitable bioindicators of the disturbance of forest ectotrophic stability. Defined stages of this disturbance can be linked directly to particular phases of impoverishment of ectomycorrhizal mycocoenoses and of enrichment of lignicolous mycocoenoses. These conclusions have been obtained from long-term research in permanent plots (1000–2500 m2) in spruce and recently also in oak and beech forests in the Czech Republic, but it seems that they are valid generally, at least in temperate forests. The analyses of proper mycorrhizae from the same plots confirmed data obtained from fruiting bodies. Both the percentage of ectomycorrhizal species and the ratio of active mycorrhizae are highly sensitive to some outer impact to forest ecosystems (air pollution, acidification, fertilization); their decrease is in negative correlation to the strong defoliation of trees and can be used for the prediction of next development in locality, at least in comparable stands, i.e., in the case of similar density of active mycorrhizae and analogous water stress. Key words: air pollution, ectomycorrhizae, ectomycorrhizal fungi, temperate forests, forest stability.
Interactions of wood decay fungi with other microorganisms, with emphasis on the degradation of cell walls
Authors: Tsuneda A. , Thorn R. G.
Published: May 2008

Interactions of two wood decay fungi, Lentinula edodes and Pleurotus ostreatus, with other wood inhabiting microorganisms were investigated on agar and in fagaceous wood, primarily by scanning electron microscopy. Micromorphologically, there were two principal modes of cell wall degradation: (i) selective removal of amorphous wall components, followed by the degradation of skeletal microfibrils, and (ii) simultaneous degradation of all wall components. These two modes were observed in three different degradation systems: (i) sapwood wall degradation by the wood decay fungi, (ii) hyphal wall degradation by mycoparasitic Trichoderma, and (iii) hyphal wall degradation by pathogenic bacteria. The simultaneous-type wall degradation in the systems i and ii was usually caused by hyphal tips. In addition to the three systems, bacteriolysis by the wood decay fungi was also studied. The bacterial cell walls, as well as microfibril bundles of wood cellulose and fungal chitin, were all fragmented into minute granules at later stages of microbial degradation and the granules were further degraded into smaller units. Frequency of occurrence and strength of mycoparasitic activity of Trichoderma harzianum were influenced by the degree of wood decay where the interaction occurred. Presence of both cellulose and chitin microfibrils apparently enhanced the mycoparasitic activity. In Quercus wood, P. ostreatus showed a unidirectional growth toward bacterial colonies, which formed as the result of decomposition of dead nematodes, and consumed the unidentified bacteria. In nitrogen-deficient wood, fungal and bacterial cell walls may serve as an important reservoir of nitrogen for wood inhabiting microorganisms. Key words: wood decay, mycoparasitism, bacteriolysis, cellulose, chitin.
The influence of nutrients on fungal growth, productivity, and sporulation during leaf breakdown in streams
Authors: Suberkropp Keller
Published: May 2008

In streams, aquatic hyphomycetes degrade leaf litter and transform it into a more suitable resource for invertebrate detritivores. Previous studies have demonstrated that fungi comprise a major portion of the microbial biomass associated with decomposing leaves and that inputs of leaves in the autumn reduce the concentration of soluble phosphorus in the water. These observations indicate that fungi obtain inorganic nutrients from the water passing over leaf surfaces. However, very little is known concerning the effects of nutrients on the activity of the fungi growing within leaves. To examine this question, I determined fungal biomass (from ergosterol concentrations) and sporulation rates during the breakdown of yellow poplar (Liriodendron tulipifera) leaves in three streams that differed in water chemistry. I also estimated instantaneous growth rates by measuring rates of [14C]acetate incorporation into ergosterol and calculated fungal productivity from growth rates and biomass. Growth rates and productivity determined by this method showed good agreement with values calculated from changes in fungal biomass during early stages of leaf breakdown for two of the streams examined. Highest concentrations of fungal biomass and greatest fungal activity occurred in the stream with the highest concentrations of nutrients. However, differences in total fungal production and biomass were not as great as were differences among sporulation rates in the three streams suggesting that fungal allocation of resources to growth and reproduction can vary depending on nutrient availability. Key words: aquatic hyphomycetes, ergosterol, leaf breakdown, nutrients, fungal productivity, streams.
Wood decomposition, higher fungi, and their role in nutrient redistribution
Authors: Boddy Lynne , Watkinson Sarah C.
Published: May 2008

Dead wood litter input to mature forest ecosystems represents 30–40% of the total biomass, containing about 1–4 and 0.1–0.8 kg/(ha∙year), of N and P, respectively. However, since wood decomposes relatively slowly, it represents a much larger proportion of the standing crop of plant litter on the forest floor, forming a large reservoir of mineral nutrients, which are unavailable for primary producers until they are released by decomposer organisms, primarily basidiomycetes and to a lesser extent ascomycetes. Readily available nutrients are utilized rapidly leaving other nutrients locked up in the recalcitrant lignocellulose complex. As decomposition proceeds the relative concentration of N and P in wood increases (i.e., carbon/nutrient ratio decreases), as C is lost as CO2, but these nutrients are rapidly sequestered in mycelial biomass. Formerly it was thought that nutrients were released when the carbon/nutrient ratio of the wood approximated that of mycelium. However, fungi are inherently greedy using excess nutrients for production of reproductive structures and foraging mycelium. The latter, which is often aggregated to form rhizomorphs or cords, grows out of wood in search of new resources, often forming extensive long-lived networks that exhibit remarkable patterns of reallocation of fungal biomass and nutrients. Within these systems, nutrients are conserved and are often relocated for many metres and may aid in establishment of mycelia in new resources. Nutrients are probably largely released when mycelia are grazed upon by invertebrates, nonbiotically damaged, interact with other fungi and bacteria, or die. Key words: ecology, lignocellulose, basidiomycetes, rhizomorph, translocation.
Fungi active in weathering of rock and stone monuments
Authors: Hirsch P. , Eckhardt F. E. W. , Palmer Jr. R. J.
Published: May 2008

Fungal colonization of sandstone and granite from Antarctica was studied. Granite from a church, sandstones from a monument and a courthouse in Germany, glazed bricks from a German cathedral, and some other stone types were also examined. All samples contained fungi and heterotrophic bacteria, often also cyanobacteria or algae. For cell counting and enrichment of microorganisms the samples were crushed aseptically, suspended in NaCl–Tween-80, plated on oligotrophic media, and incubated at 16–25 °C dark or in dim light. Total biomass was determined as phospholipid-bound phosphate (PLP). Rock samples were also viewed by electron microscopy. Typical viable fungal cell numbers (CFU∙g−1 dry weight) were the following: sandstone 1.6 × 104, granite 6.2 × 105, and glazed bricks 1.2 × 105. Total biomass ranged from 41 (sandstone) to 137 (glaze) nmol PLP∙g−1 dry weight; antarctic sandstone had 88 nmol PLP∙g−1. Fungal genera identified were the following: Alternaria, Aspergillus, Aureobasidium, Candida, Cladosporium, Paecilomyces, Phoma, Penicillium, and Sporobolomyces. Scanning electron microscopy revealed fungal bridging of open spaces with their hyphae or close contact between fungal hyphae and coccal cells believed to be algae. In some cases fungi were found to produce secondary minerals or their hyphae were covered with partially etched mineral layers. Exopolymer formation was common among the endolithic microorganisms. Mites were found to feed on epiliths. In pure culture, fungi from sandstone produced in 24 h cultures organic acids (citrate, glutamate, pyruvate, malate, succinate, lactate, formate, fumarate, and oxalate). Many of these acids could also be extracted from rock samples. Fungal growth on glucose and mineral powder resulted in up to 60% cation extraction from the mineral. Some fungi were antibiotically active against bacteria or yeasts but also stimulated other bacterial isolates. In summary, epi- and endo-lithic communities contained fungi that probably contribute substantially to the deterioration of many stones and monuments. Key words: rock weathering, biomass, acid excretion, cation extraction.
Fungal communities in wet tropical forests: variation in time and space
Authors: Lodge D. Jean , Cantrell Sharon
Published: May 2008

Understanding variation in tropical forest fungal populations and communities is important for assessing fungal biodiversity, as well as for understanding the regulatory roles fungi play in tropical forests. In wet tropical forests, the canopy is typically occupied by certain wood decomposers, endophytes, epiphylls, and pathogens. Aphyllophoraceous canopy fungi are a subset of species found in the understory. Marasmioid agarics in the understory often form extensive networks of rhizomorphs that trap litter; these and other aerial species are rare on the forest floor. Decomposers are stratified within the forest floor, with some species colonizing only fresh litter, others preferring decomposed litter, and others restricted to soil organic matter. Specificity to particular host substrates is frequent among tropical forest litter decomposers and contributes to spatial heterogeneity in fungal communities over the landscape. Litter basidiomycete and microfungal communities in patches of 1 m2 or less do not significantly resemble communities in similar patches located at distances greater than 100 m. Disturbances induce changes in the environment and the abundance of different substrates, resulting in changes in fungal communities through time, and variation over the landscape. Severe disturbances, as well as the slight daily variations in rainfall, profoundly affect populations of fungal decomposers and their influence on plant nutrient availability. Key words: fungi, tropical forests, diversity, stratification, spatial variation, temporal variation.
Association of ectomycorrhizal fungi with decomposed animal wastes in forest habitats: a cleaning symbiosis?
Authors: Sagara Naohiko
Published: May 2008

A new tripartite relationship among animals, fungi, and plants, based on formation of ectomycorrhiza and on removal of animal wastes, is described. In forest habitats where animal wastes such as urine or faeces or dead bodies, mainly of mammals, have been deposited, a particular group of fungi form reproductive structures successionally after the apparent decomposition of the wastes. This natural event can be simulated by application to the soil of urea, aqueous ammonia, or nitrogen compounds that release ammonia on decomposition. Both field observations and simulation experiments show that, when these events take place in forests of ectomycorrhizal trees, ectomycorrhizal fungi fruit during the late phase in the succession. Ectomycorrhizas are in fact observed in the soils colonized by these fungi. Among these fungi, Hebeloma spp., Laccaria spp., and a few others colonize commonly in various waste sites, while Hebeloma radicosum colonizes specifically in moles’ deserted middens (latrines) near their nests. The animals involved here as waste depositors or cadavers seem not to feed on the fungi and the plants but may depend on them for cleaning their own habitats, since mycorrhizas should readily remove products derived from wastes. The tripartite relationship described may be viewed as a cleaning symbiosis. Key words: animal waste, ammonia, postputrefaction fungi, Hebeloma, ectomycorrhiza, cleaning symbiosis.
Concentration and Distribution of PCB Congeners in Isolated Ontario Lakes Contaminated by Atmospheric Deposition
Authors: Macdonald C. R. , Metcalfe C. D.
Published: May 2008

The concentration of 19 PCB congeners was analysed in biota, sediments, water, and suspended solids in four central Ontario lakes in which atmospheric deposition was the major source of PCB contamination. Input from the atmosphere resulted in total congener concentrations of 1–2 ng∙L−1 dissolved in water, 10–50 μg∙kg−1 (dry weight} in sediment, 5–10 μg∙kg−1 (wet weight) in biota from lower trophic levels (i.e. zooplankton, golden shiner (Notemigonus crysoleucas)), and 10–30 μg∙kg−1 (wet weight) in fish from upper trophic levels (yellow perch (Perca fiavescens), smallmouth bass (Micropterus dolomieui)). The dominant PCB congeners in the lakes were the trichlorobiphenyl congeners 31(28} and the hexachlorobiphenyl congeners 153 and 138, consistent with congener distributions reported for vapour- and particulate-bound PCBs in the atmosphere. Discriminant analysis indicated slight differences in congener patterns between the study lakes, but the general pattern for isolated lakes was substantially different from point-source contaminated lakes, primarily due to the high proportion of congeners 31(28). There was no significant difference in the total PCB concentrations in biota (lipid basis) between lakes, but within the lakes, total PCB concentrations were significantly higher in yellow perch than in biota from lower trophic levels.
Adrenergic Response to Physiological Disturbances in Rainbow TroutfOncorhynchus mykiss, Exposed to Aluminum at Acid pH
Authors: Witters H. E. , Puymbroeck S. Van , Vanderborght O. L. J.
Published: May 2008

A 10-fold increase of plasma epinephrine and norepinephrine levels was evident at 46 h of Al exposure in adult rainbow trout, Oncorhynchus mykiss, which were kept for about 2.5 d at pH 5.0 with 60 μg Al/L (Ca2+ = 28 μmol/L). The change of plasma epinephrine levels was related both to the decrease of the blood pH and the decrease of the blood [Formula: see text]. We further observed decreased plasma Na+concentrations which were accompanied by elevated levels of Cortisol in the plasma of Al-exposed fish. Exposure of fish to pH 6.8 (= control) or pH 5.0 without Al did not yield any changes in plasma Na+concentrations, plasma Cortisol concentrations, blood pH, blood [Formula: see text], and plasma epinephrine, norepinephrine, and dopamine levels. The release of plasma catecholamines associated with blood acidosis and hypoxia is suggested to be an important factor in maintaining erythrocytic pH to protect the haemoglobin oxygen carrying capacity in fish exposed to low pH and Al.
Lack of Biological Activities in the Extracellular Products of Renibacterium salmoninarum
Authors: Bandin I. , Santos Y. , Bruno D. W. , Raynard R. S. , Toranzo A. E. , Barja J. L.
Published: May 2008

Evaluation in vivo and in vitro of the extracellular products (ECP) of a group of Renibacterium salmoninarum strains from different geographic origins revealed a low production of extracellular proteins in all strains and confirmed that most of the isolates were poor producers of proteolytic enzymes. The ECP displayed neither haemolytic activity nor capacity to alter the osmotic equilibrium of fish erythrocytes. In addition, none of the ECP samples displayed cytotoxic activities regardless of the origin of the cell line employed and did not contain substances lethal for fish, since no mortalities were recorded when doses ranging from 10 to 20 μg protein/g fish were administered. Although the present work failed to demonstrate toxicity in vivo of the ECP, it is possible that some extracellular enzymes contribute to the weakening of fish during the disease process and allow bacterial survival.
Large-Scale Escapes of Farmed Atlantic Salmon (Salmo salar) into Norwegian Rivers Threaten Natural Populations
Authors: Gausen D. , Moen V.
Published: May 2008

We present data on Atlantic salmon (Salmo salar) which show that escaped farmed salmon enter Norwegian rivers in great numbers. Escaped farmed salmon comprised a substantial proportion of the mature salmon present on the spawning grounds in autumn. A potential for large-scale genetic introgression thus exists. The sex ratios, length distributions, and times of ascent of wild and farmed salmon differed significantly, reflecting major variations in biology and behavior. High proportions of farmed salmon (> 20%) were found only in rivers having fish farms situated closer than 20 km from the outlet.
Whelk (Buccinum undatum) Movement and Its Implications for the Use of Tag–Recapture Methods for the Determination of Baited Trap Fishing Parameters
Authors: Sainte-Marie Bernard
Published: May 2008

The tag–recapture method has been used to measure the field of attraction and the effective fishing area of a baited trap. The possibly conflicting experimental conditions required for the determination of these two parameters are, respectively, that tagged animals do not move and that they behave as undisturbed animals, prior to exposure to bait odour. Field observations and in situ experiments were conducted on the north shore of the Gulf of Saint Lawrence in 1988 and 1989 to compare behaviour of undisturbed and tagged whelks (Buccinum undatum). In the daytime, ~ 75% of undisturbed whelks were quiescent, being either buried and oriented randomly or static and oriented downstream, while the remainder moved across stream at 2–5 cm∙min−1. In contrast, > 97% of tagged whelks oriented in nonrandom directions and moved at equal or greater speeds, on average, 2.2–9.2 m from release points in less than 6 h. Because neither of the two basic conditions was met, tag–recapture experiments would produce biased estimates of baited trap fishing parameters.
Allometric Scaling of Light Absorption and Scattering by Phytoplankton Cells
Authors: Agustí Susana
Published: May 2008

Examination of the allometric scaling of light absorption (acell) and scattering (bcell) by 28 phytoplankton species showed that light absorption is scaled to the cross-sectional area of the cells (log acell(square micrometres per cell) = −1.06 + 2.32 log d (micrometres)) whereas light scattering is scaled to their volume (log bcell(square micrometres per cell) = −1.09 + 3.45 log d (micrometres)). The scaling of light absorption to the cross-sectional area of algal cells is explained by a decrease in intracellular chlorophyll a concentration as cell size increases, thereby avoiding inefficient light capture by photosynthetic pigments. The scaling of light scattering to cell volume conforms to the general theory for large particles (Mie theory). Light absorption by phytoplankton cells, unlike light scattering, deviates from that of nonliving particles because of the covariation between pigment content and cell size that help prevent self-shading.
Indirect Effects of Detritus Manipulations in a Montane Stream
Authors: Richardson John S. , Neill William E.
Published: May 2008

To evaluate the common assumption in stream ecosystem theory that fine-particle feeders can indirectly benefit from coarse-particle detritus consumed by detritivores, we manipulated whole-leaf detritus in replicated experimental stream channels. Elevated input rates of detritus resulted in significantly higher densities of collectors and moderate but nonsignificantly higher densities of predators. When collectors were analyzed as filterers and gatherers separately, there were significantly higher densities of both groups at a high loading rate of leaves. The net rates of colonization for each trophic group did not differ significantly with respect to treatment, which suggests that the increased densities of collectors observed under high leaf input rates were due to increased survival of larvae. Density of no single taxon increased significantly in response to coarse particulate organic matter inputs; rather, most species showed moderate increases. Species richness showed no treatment effect. Increases in collector density may result indirectly from increased fine particulate organic matter production due to feeding by shredders. Predaceous species which responded were small taxa and were probably predators on collectors. These effects were observed over a period of less than 5 mo and demonstrate the potential strength of the interactions.