Mycological research最新文献

Three endophytic yeast, one isolated from stems of wild cottonwood (Populus trichocarpa), two from stems of hybrid poplar (P. trichocarpa × Populus deltoides), were characterized by analyzing three ribosomal genes, the small subunit (18S), internal transcribed spacer (ITS), and D1/D2 region of the large subunit (26S). Phenotypic characteristics of the yeast isolates were also obtained using a commercial yeast identification kit and used for assisting the species identification. The isolate from wild cottonwood was identified to be closest to species Rhodotorula graminis. The two isolates from hybrid poplar were identified to be species Rhodotorula mucilaginosa. In addition, the three yeast isolates were observed to be able to produce indole-3-acetic acid (IAA), a phytohormone which can promote plant growth, when incubated with l-tryptophan. To our knowledge, the yeast strains presented in this study were the first endophytic yeast strains isolated from species of Populus.

Penicillium marneffei is an important opportunistic dimorphic fungal pathogen that can cause fatal systemic mycosis in AIDS patients. To find new ways of overcoming infection, candidate virulence associated genes and virulence mechanisms are under intensive investigation. In the present study, we have examined the function of a novel P. marneffei histidine kinase gene (PmHHK1) using dsRNAi mediated by Agrobacterium tumefaciens. Our results showed that reduction of PmHHK1 expression produces significant changes in morphogenesis (including polarized growth), sporulation and cell wall composition. Two-component signaling systems are widespread in the eukaryotes outside the animal kingdom, and could be potential drug targets for antifungal chemotherapy.

The fungal community associated with the terrestrial photosynthetic orchid Gymnadenia conopsea was characterized through PCR-amplification directly from root extracted DNA and cloning of the PCR products. Six populations in two geographically distinct regions in Germany were investigated. New ITS-primers amplifying a wide taxonomic range including Basidiomycetes and Ascomycetes revealed a high taxonomic and ecological diversity of fungal associates, including typical orchid mycorrhizas of the Tulasnellaceae and Ceratobasidiaceae as well as several ectomycorrhizal taxa of the Pezizales. The wide spectrum of potential mycorrhizal partners may contribute to this orchid's ability to colonize different habitat types with their characteristic microbial communities. The fungal community of G. conopsea showed a clear spatial structure. With 43 % shared taxa the species composition of the two regions showed only little overlap. Regardless of regions, populations were highly variable concerning taxon richness, varying between 5 and 14 taxa per population. The spatial structure and the continuous presence of mycorrhizal taxa on the one hand and the low specificity towards certain fungal taxa on the other hand suggest that the fungal community associated with G. conopsea is determined by multiple factors. In this context, germination as well as pronounced morphological and genetic differentiation within G. conopsea deserve attention as potential factors affecting the composition of the fungal community.

Harpellales (Legeriomycetaceae, Zygomycota) or ‘trichomycetes’ are fungi that inhabit the digestive tracts of arthropods such as insects, millipedes, and crustaceans. In the current study we examined changes in 5 morphological characters of Smittium culisetae (Harpellales: Legeriomycetaceae) between the two dipteran (mosquito, black fly) hosts reared under 3 different temperatures (17, 22, 30 °C). Both host and temperature had a pervasive effect on the linear dimension of trichospores, their generative cells and hyphae width. At 30 °C the mean size of all 5 morphological characters were consistently larger in fungus taken from the mosquito host than from the black fly host. At 17 °C and 22 °C, however, there were no consistent patterns. The effect of host was so pronounced that it could be accurately determined which host S. culisetae colonised based on differences in linear morphology. Such changes in fungal morphology between hosts have important ramifications for the morphologically based taxonomy of this group.

Conifer twigs showing brown felt blight were collected along 100-m long transects at the timberline in the Swiss Alps and single-hyphal-tip cultures were prepared. Forty-seven of the sequenced 48 strains were Herpotrichia juniperi based on sequence comparisons of the internal transcribed spacers (ITS). A non-sporulating strain was tentatively identified as another, undescribed Herpotrichia species. Herpotrichia coulteri was not isolated. Most strains were from Juniperus communis var. saxatilis, the rest from Picea abies and Pinus mugo. Each twig was colonized by a different genotype as revealed by ISSR-PCR fingerprinting. More than one clone was present on some needles and twigs. Thus, importance of vegetative mycelial growth for dispersal seems to be limited to the spread of the disease to twigs of the same tree or of immediately adjacent trees, and, consequently, dispersal occurs mainly by ascospores. The H. juniperi strains could be assigned to five distinct groups based on the ISSR-PCR data. The strains from P. abies formed one of these groups but the other groups did not correlate with either host, transect or position along the transects. Multi-locus analysis based on β-tubulin, elongation factor 1-α and ITS sequences confirmed the subdivision into five groups. Population differentiation among groups was distinct with N_ST values varying between 0.545 and 0.895. H. juniperi seems to be composed of several cryptic species, one of them specific to P. abies.

Evidence suggests that truffle-like sporocarp forms have evolved many times in the Pezizales, but primarily from epigeous ancestors within ectomycorrhizal clades. There are several ectomycorrhizal clades, however, that contain no known hypogeous species. We collected specimens of an unusual unidentified truffle from mixed oak woodlands in Iowa. Although clearly a member of the Pezizales (Ascomycota), this hypogeous species did not belong to any of the described truffle genera. Based on a combination of ecological, phylogenetic, and morphological evidence we determined that this new truffle is a hypogeous member of the genus Otidea (Pyronemataceae), a lineage with no described truffle species. We describe it here as a new species, Otidea subterranea.

For the first time, the specific activities of chitinases, esterases, lipases and a serine protease (VCP1) produced by different isolates of the nematophagous fungus Pochonia chlamydosporia were quantified and compared. The isolates were grown for different time periods in a minimal liquid medium or media supplemented with 1 % chitin, 0.2 % gelatin or 2 % olive oil. Enzyme-specific activities were quantified in filtered culture supernatants using chromogenic p-nitrophenyl substrates (for chitinases, lipases and esterases) and a p-nitroanilide substrate (to measure the activity of the proteinase VCP1). Additionally, information on parasitic growth (nematode egg parasitism) and saprotrophic growth (plant rhizosphere colonisation) was collected. Results showed that the production of extracellular enzymes was influenced by the type of medium (p < 0.05) in which P. chlamydosporia was grown. Enzyme activity differed with time (p < 0.05), and significant differences were found between isolates (p < 0.001) and the amounts of enzymes produced (p < 0.001). However, no significant relationships were found between enzyme activities and parasitic or saprotrophic growth using Kendall's coefficient of concordance or Spearman rank correlation coefficient. The results provided new information about enzyme production in P. chlamydosporia and suggested that the mechanisms which regulate the trophic switch in this fungus are complex and dependent on several factors.