Mycologia

Published by Mycological Society of America
Online ISSN: 1557-2536
Publications
Article
We have approached the problem of hyphal tip growth by comparing the cell wall composition of elongating and non-elongating regions of the hyphae of Achlya bisexualis. To ensure that we could distinguish between elongating and non-elongating hyphae, light microscopic observations were used to determine the rates of elongation under growing and non-growing conditions. When elongation was measured in 10 min intervals it was found to consist of fluctuating periods of fast and slow growth rates, in the form of cycles. Even under our growing conditions, however, a very small number of hyphae in a colony are not elongating. SEM analysis revealed that elongating hyphae have tapered apices, whereas non-elongating hyphae have a rounded apex. The major matrix wall components, 1,3-β-glucans, were localized with an indirect immunogold technique specific for these polymers. This method resulted in their localization to all regions of both elongating and non-elongating hyphae, including the apex.
 
Article
The hemibiotrophic fungus Mycosphaerella fijiensis is the causal agent of black Sigatoka disease (BS), the most devastating foliar disease in banana (Musa spp.) worldwide. Little is known about genes that are important during M. fijiensis-Musa sp. interaction. The fungal cell wall is an attractive area of study because is essential for maintenance of cellular homeostasis and it is the most external structure in the fungal cell and therefore mediates the interaction of the pathogen with the host. In this manuscript we describe the in silico identification of glycosyl phosphatidylinositol-protein (GPI) family in M. fijiensis, and the analysis of two β-1,3-glucanosyltransferases (Gas), selected by homology with fungal pathogenicity factors. Potential roles in pathogenesis were evaluated through analyzing expression during different stages of black Sigatoka disease, comparing expression data with BS symptoms and fungal biomass inside leaves. Real-time quantitative RT-PCR showed nearly constant expression of MfGAS1 with slightly increases (about threefold) in conidia and at speck-necrotrophic stage during banana-pathogen interaction. Conversely, MfGAS2 expression was increased during biotrophy (about 7 times), and then reached a maximum at speck (about 23 times) followed by a progressive decrease in next stages, suggesting an active role in M. fijiensis pathogenesis.
 
Time course of degradation of carboxymethylcellulose followed viscometrically (▫) and reductimetrically (). The data points obscure error bars. 
Article
Models of wall loosening in fungi and other walled eukaryotes require the action of proteins able to reduce the degree of linkage between components of the wall. In the oomycete Achlya ambisexualis, such a role has been proposed for a suite of endoglucanases that are secreted during branching and during the measurable wall softening associated with osmotic stress. We report here the isolation and characterization of one of these isoenzymes. The enzyme has a molecular weight of 32 kDa, a pH optimum of 6.75, a pI of 4.5, and a temperature optimum of 35 C. It is partially inhibited by sulfhydryl-binding reagents and completely inhibited by the tryptophan-binding reagent NBS. The enzyme has an endohydrolytic mode of action with substrate specificity towards glucans that contain β-(1,4) linkages, either alone (carboxymethyl cellulose) or as mixed linkage (1,4-1,3)-β-glucans (e.g., Avena glucan). It does not, however, degrade amorphous insoluble (phosphoric acid swollen) cellulose. Most significantly, the enzyme can also hydrolyze linkages in an Achlya cell wall fraction previously shown to consist of a mixed-linkage (1,4-1,3)-β-glucan. This property is consistent with the long-standing hypothesis that the branching-related endoglucanases of oomycetes play a role in cell wall loosening.
 
Article
To degrade the polysaccharides, wood-decay fungi secrete a variety of glycoside hydrolases (GHs) and carbohydrate esterases (CEs) classified into various sequence-based families of carbohydrate-active enzymes (CAZys) and their appended carbohydrate-binding modules (CBM). Oxidative enzymes, such as cellobiose dehydrogenase (CDH) and lytic polysaccharide monooxygenase (LPMO, formerly GH61), also have been implicated in cellulose degradation. To examine polysaccharide-degrading potential between white- and brown-rot fungi, we performed genomewide analysis of CAZys and these oxidative enzymes in 11 Polyporales, including recently sequenced monokaryotic strains of Bjerkandera adusta, Ganoderma sp. and Phlebia brevispora. Furthermore, we conducted comparative secretome analysis of seven Polyporales grown on wood culture. As a result, it was found that genes encoding cellulases belonging to families GH6, GH7, GH9 and carbohydrate-binding module family CBM1 are lacking in genomes of brown-rot polyporales. In addition, the presence of CDH and the expansion of LPMO were observed only in white-rot genomes. Indeed, GH6, GH7, CDH and LPMO peptides were identified only in white-rot polypores. Genes encoding aldose 1-epimerase (ALE), previously detected with CDH and cellulases in the culture filtrates, also were identified in white-rot genomes, suggesting a physiological connection between ALE, CDH, cellulase and possibly LPMO. For hemicellulose degradation, genes and peptides corresponding to GH74 xyloglucanase, GH10 endo-xylanase, GH79 β-glucuronidase, CE1 acetyl xylan esterase and CE15 glucuronoyl methylesterase were significantly increased in white-rot genomes compared to brown-rot genomes. Overall, relative to brown-rot Polyporales, white-rot Polyporales maintain greater enzymatic diversity supporting lignocellulose attack.
 
Article
The culture and reproductive systems of 10 species (16 isolates) of myxomycetes and one species (one isolate) of protostelid were investigated. A single isolate of Ceratiomyxa fructiculosa was grown on agar and found to be nonheterothallic. This is the first report of spore-to-spore cultivation of this species and the first report of a reproductive system in the protostelids. Isolates of the myxomycetes Didymium dubium, Didymium iridis, Didymium vaccinum, Licea biforis, Perichaena vermicularis, Physarum gyrosum, Physarum pusillum (six isolates) and Semimorula liquescens all were nonheterothallic. This is the first report of culture and a reproductive system for D. vaccinum, the first report of nonheterothallism for S. liquescens and the second report of nonheterothallic isolates of D. dubium, Licea biforis, Perichaena vermicularis and P. gyrosum. The nonheterothallic isolate of D. iridis is one of many reported for this species, and the six nonheterothallic isolates of P. pusillum add to the seven nonheterothallic and two heterothallic isolates already known. In addition, five of the isolates of P. pusillum apparently represent a small form that is adapted to an ephemeral micohabitat, and the sixth is a yellow form of a species that is typically white. The Didymium ?ovoideum isolate and the two Physarum didermoides isolates have heterothallic reproductive systems. The D. ?ovoideum isolate is somewhat different from most isolates of this species in its morphology and reproductive system. It is not compatible with any of the heterothallic isolates of long-stalked Didymium, including the A0 biological species already determined for D. ovoideum; therefore, it is either a new biological species of D. ovoideum or a separate new species. The two heterothallic isolates of P. didermoides form a multiple allelic mating-type series with four alleles.
 
Article
(13)C-NMR analyses of Cantharellus cibarius growth media were performed. We found exudation of trehalose and mannitol, which may explain the phenomenon of reproducing Pseudomonas bacteria observed inside fruit bodies. Exudation varied with strain and environment. NMR analyses of stored (13)C was also performed. Trehalose, mannitol, and arginine were revealed. The mannitol pathway seems to play an important role for trehalose production in this species. This is the first study of the fate of the photosynthetically derived carbon in the highly appreciated edible ectomycorrhizal mushroom Cantharellus cibarius.
 
Article
The exocellular chitinase system of Chytriomyces hyalinus Karling has been studied. The conditions necessary for obtaining a high yield of chitinase and a procedure for concentrating the enzyme are given. The activity of the crude chitinase was assayed using a C14-chitin decomposition assay. This assay is based on the use of C14-chitin as the enzyme substrate. With the radioactivity of the substrate known, the amounts of radioactivity released into solution by chitinase under different conditions can be compared. The C14-chitin is obtained by growing the fungus Allomyces macrogynus (Emerson) Emerson & Wilson on C14-glucose. The fungus incorporates C14-chitin substrate. The optimum temperature for chitinase activity is 25 C, the optimum pH is 5.5. The Michaelis constant of the crude chitinase is 5.7 μmoles of reducing sugar per mg of protein. Chitinase activity is not inhibited by N-acetylglucosamine or glucose. Copper and cadmium ions cause almost total inhibition. Potassium, sodium, magnesium, lithium and cobalt ions all cause some inhibition of chitinase activity.
 
Article
The current postulate that organic acids added to a culture medium affect growth of fungi only by buffering the medium was tested by culturing Claviceps purpurea PRL 1980 in a medium containing glucose, ammonia, salts and 2, $3-^{14}\text{C}$-succinate and analyzing various fractions of the mycelium for the presence of radioactivity. In addition, radioactivity of respired CO2 was measured. It was found that succinate was taken up before growth was evident and was assimilated and respired both before and after exogenous glucose was consumed. Radioactivity appeared in the hot water extract, ether-ethanol extract, hot TCA extract, protein extract, and in the crude cell wall preparation as well as in two sugars isolated from the cell wall. Thus, exogenous succinate participated in metabolism and did not influence the culture only in its capacity as a buffer.
 
Article
“There are…subjects for which I have more than ordinary affection because they are associated in my mind with kindly and understanding men or women—sculptors who left even upon such impliant clay as mine the delicate chiseling of refined genius, who gave unwittingly, in other words, something of their final character to most unpromising material. Sculptors reaching blindly forward into time, they struck out their creation scarcely living to see the result.”
 
Article
The effect of litter type and incubation temperature on the ability of fungi to decompose leaf litter of subalpine trees was examined by a pure-culture test. Mass loss of Abies needle and Betula leaf litter and utilization patterns of lignin and carbohydrates were investigated under two temperature conditions (20 C and 10 C) and compared for 29 species in basidiomycetes, ascomycetes and zygomycetes. The decomposing ability was generally higher in basidiomycetes than in ascomycetes and zygomycetes. Mass loss (% original mass) of litter was higher in Betula than in Abies and higher at 20 C than at 10 C. The 29 fungi were divided into lignocellulose decomposers, cellulose decomposers and sugar fungi based on their substrate utilization in Abies and Betula litter. Mass loss of lignin and carbohydrates by lignocellulose and cellulose decomposers was higher in Betula than in Abies. Mass loss of carbohydrates was higher at 20 C than at 10 C, but the temperature did not influence mass loss of lignin, indicating lignin decomposition by fungi was less sensitive to temperature than carbohydrate decomposition. Lignin/carbohydrate loss ratio (L/C) of Collybia spp. that caused selective delignification was lower at 20 C than at 10 C. These results indicate that the decomposability of litter, lignin and carbohydrate was different between Abies and Betula and that temperature affected not only the rate at which fungi decompose litter but also the ability of fungi to use lignin and carbohydrates.
 
Article
Solioccasus polychromus gen. & sp. nov., the most brightly colored hypogeous fungus known, is described from Papua New Guinea and tropical northern Australia south into subtropical forests along the Queensland coast and coastal mountains to near Brisbane. Phylogenetic analysis of molecular data places it as a sister genus to Bothia in the Boletineae, a clade of predominantly ectomycorrhizal boletes. Ectomycorrhizal trees, such as members of the Myrtaceae (Eucalyptus, Corymbia, Lophostemon, Melaleuca spp.) and Allocasuarina littoralis, were present usually in mixture or in some cases dominant, so we infer some or all of them to be among the ectomycorrhizal hosts of S. polychromus.
 
Article
Berkleasmium crunisia sp. nov. is described from a decaying rachis of Calamus sp. (Arecaceae) from Khuan Ka Long, Satun Province, Thailand. This Berkleasmium species differs morphologically from other species in possessing subtending cells and larger conidia. The phylogenetic relationship of the genus Berkleasmium among sexual ascomycetes also was examined. Sequence analyses from 18S, 28S and ITS-5.8S rDNA were analyzed phylogenetically under maximum parsimony, Bayesian and neighbor joining criteria. Phylogenies revealed that Berkleasmium is not monophyletic. Berkleasmium micronesicum and B. nigroapicale are related to Westerdykella cylindrica and Sporormia australis, which are members of the family Sporormiaceae (Pleosporales). Other species, including our new taxon, appear to share phylogenetic affinities with other anamorphic fungi, whose classification within the Pleosporales is still obscure. Analyses of 18S, 28S, ITS (+5.8S) rDNA and combined (18S+28S) gene sequences fail to give sufficient phylogenetic resolution within the Pleosporales.
 
Article
Nuclear-encoded small-subunit ribosomal DNA was used to examine phylogenetic relationships in Paecilomyces sensu lato. Phylogenetic analysis of the 18S nr DNA demonstrates that Paecilomyces is polyphyletic across two subclasses, Sordariomycetidae and Eurotiomycetidae. The type species, Paecilomyces variotii, and thermophilic relatives belong in the order Eurotiales (Trichocomaceae), while mesophilic species related to Paecilomyces farinosus are in the order Hypocreales (Clavicipitaceae and Hypocreaceae). One species, Paecilomyces inflatus, had affinities for the order Sordariales. Within the Eurotiales, Paecilomyces is monophyletic. Within the Hypocreales, species of Paecilomyces are polyphyletic, although the data failed to fully resolve these relationships.
 
Article
An extensive, as well as an intensive, study was made of white corn under government loan as it was delivered in 1972 to the Agricultural Stabilization and Conservation Service at Diehlstadt, Missouri. The corn (450,000 bu) came from 77 loans and had been stored on farms. From each of the 1,283 trucks representative samples of corn were taken and ground for aflatoxin assay; a small portion was used to streak plates of yeast extract agar containing tetracycline. After incubation for 5 days at 28 C, the plates were read under a dissecting microscope for the common types of molds with special emphasis on the presence of the Aspergillus flavus group. A rough estimation was made of the A. flavus colonies per plate. Other molds recorded were A. niger, A. fumigatus, A. terreus, A. glaucus group; species of Trichoderma, Penicillium, Fusarium, Rhizopus, Mucor, and Absidia. Of the 1,283 samples, each representing a truckload of corn, 394 contained aflatoxin, and of these, A. flavus group was present in all but seven. The molds most common in the 1,283 samples were Penicillium sp. (94%), Fusarium sp. (89%), A. flavus (82%), and A. niger (71%). Aspergillus parasiticus was seen in only 15 times. No correlation seemed to exist between the grade of corn and the presence of A. flavus. However with some molds, a higher percentage occurred in the poorer grades. When actual counts of A. flavus were made on corn from three loans, the occurrence of A. flavus closely paralleled the aflatoxin content of the corn samples.
 
Article
A discomycete, Pyronema domesticum, was grown on medium containing 500 ppm 2,4-dichlorophenoxyacetic acid. Although many gametangia and apothecia appeared to develop normally on this medium, abnormalities were commonplace. Abnormalities included a reduction in the total number of ascogonia and antheridia formed in a gametangial cluster, malformed gametangia, fusion of the trichogyne with a structure other than the antheridium, failure for plasmogamy to be completed, the apomictic production of ascogenous hyphae, and the conversion of apothecia into sterile sclerotium-like structures. In addition, the 2,4-D caused a 2-5 day delay in the maturation of all apothecia.
 
Article
Sixteen streams in middle and eastern Tennessee were surveyed for the sudden oak death pathogen Phytophthora ramorum 2010-2012. Surveys were conducted in the spring and fall using healthy Rhododendron leaves and a total of 354 oomycete isolates were recovered. Sequence analysis of the ITS region provisionally identified 151 Phytophthora, 200 Pythium, 2 Halophytophthora and 1 Phytopythium. These include six Phytophthora species (P. cryptogea, P. hydropathica, P. irrigata, P. gonapodyides, P. lacustris and P. polonica), members of the P. citricola species complex, five unknown Phytophthora species, eleven Pythium species (P. helicoides, P. diclinum, P. litorale, P. senticosum, P. undulatum, P. vexans, P. citrinum, P. apleroticum, P. chamaihyphon, P. montanum and P. pyrilobum), three unknown Pythium species, Halophytophthora batemanensis, and one Phytopythium isolate. The biology and implications are discussed.
 
Article
Most of what is known about the distribution of protostelids is limited to results from surveys carried out in North and Central America. To increase our knowledge about protostelid diversity and distribution we surveyed protostelids from 12 study sites in northern Queensland and the Northern Territory of Australia during May-Jun 2003. Aerial litter and ground litter samples were randomly collected along a 200 m transect at each site. Study sites ranged from tropical forests to deserts. We recovered 10 species and two apparently undescribed species from samples of aerial (dead but still attached plant parts) and ground litter. Samples from a woodland site characterized by intermediate moisture conditions had the greatest species richness, followed by samples from dry woodland, tropical forest and desert sites. When species richness for a particular microhabitat was considered, samples of aerial litter yielded more species than samples of ground litter. Percentages of samples colonized with protostelids were similar for the aerial and ground litter microhabitats within a given habitat type except for dry woodlands, in which aerial litter samples were characterized by higher numbers of species than ground litter samples. Two species (Protostelium mycophaga and Soliformovum irregularis) that in temperate North America are associated with aerial litter microhabitats also were recovered from aerial litter in dry habitats in Australia. Schizoplasmodiopsis pseudoendospora, a North American temperate ground litter species, was equally abundant in aerial litter and ground litter in Australia. This study is the first of its kind for protostelid ecology in Australia and the most extensive study of protostelids in the southern hemisphere. These data complement ongoing research on protostelid distribution from around the world.
 
Top-cited authors
Michael J. Wingfield
  • University of Pretoria
Brenda D Wingfield
  • University of Pretoria
James F White
  • Rutgers, The State University of New Jersey
Pedro W Crous
  • Westerdijk Fungal Biodiversity Institute
Teresa Coutinho
  • University of Pretoria