Mycological research最新文献

While it is established that increasing atmospheric inorganic nitrogen (N) deposition reduces ectomycorrhizal fungal biomass and shifts the relative abundances of fungal species, little is known about effects of organic N deposition. The effects of organic and inorganic N deposition on ectomycorrhizal fungi may differ because responses to inorganic N deposition may reflect C-limitation. To compare the effects of organic and inorganic N additions on ectomycorrhizal fungi, and to assess whether host species may influence the response of ectomycorrhizal fungi to N additions, we conducted an N addition experiment at a field site in the New Jersey pine barrens. Seedlings of two host species, Quercus velutina (black oak) and Pinus rigida (pitch pine), were planted at the base of randomly-selected mature pitch pine trees. Nitrogen was added as glutamic acid, ammonium, or nitrate at a rate equivalent to 227.5 kg ha⁻¹ y⁻¹ for eight weeks, to achieve a total application of 35 kg ha⁻¹ during the 10-week study period. Organic and inorganic N additions differed in their effects on total ectomycorrhizal root tip abundance across hosts, and these effects differed for individual morphotypes between oak and pine seedlings. Mycorrhizal root tip abundance across hosts was 90 % higher on seedlings receiving organic N compared to seedlings in the control treatment, while abundances were similar among seedlings receiving the inorganic N treatments and seedlings in the control. On oak, 33–83 % of the most-common morphotypes exhibited increased root tip abundances in response to the three forms of N, relative to the control. On pine, 33–66 % of the most-common morphotypes exhibited decreased root tip abundance in response to inorganic N, while responses to organic N were mixed. Plant chemistry and regression analyses suggested that, on oak seedlings, mycorrhizal colonization increased in response to N limitation. In contrast, pine root and shoot N and C contents did not vary in response to any form of N added, and mycorrhizal root tip abundance was not associated with seedling N or C status, indicating that pine received sufficient N. These results suggest that in situ organic and inorganic N additions differentially affect ectomycorrhizal root tip abundance and that ectomycorrhizal fungal responses to N addition may be mediated by host tree species.

Members of the mitosporic fungal form-genus Stachybotrys, including common indoor contaminants Stachybotrys chartarum, Stachybotrys echinata and Stachybotrys chlorohalonata, are capable of producing potent, protein synthesis-inhibiting, trichothecene mycotoxins. A combined multi-gene approach was used to investigate relationships among species of Stachybotrys against which the presence/absence of the trichothecene biosynthetic pathway gene, trichodiene synthase (tri5), was evaluated. Phylogenetic analyses partitioned species of Stachybotrys into three strongly supported lineages, two of which contained common indoor taxa. No tri5 PCR product was amplified from members of the third clade, which included the only member of the group with a known sexual state, Stachybotrys albipes. Isolates grouped with S. albipes also tested negative for tri5 in Southern analyses. The phylogenetic distribution of tri5 was consistent with known toxin production for the group. For isolates with tri5 product, Bayesian analysis suggested that signal from amino acid determining sites conflicted with the combined phylogeny. Incongruence however, was not supported by either SH-test results or maximum likelihood analyses. Moreover, sites rates analysis showed that tri5 was highly conserved at the amino acid level suggesting that identity at variable sites, among otherwise divergent taxa, might be the result of chance events.

Most ‘ambrosia’ fungi are members of a heterogeneous group of ophiostomatoids that includes the anamorph genera Ambrosiella, Raffaelea and Dryadomyces. The taxonomy of these fungi based on morphological features has been complicated by these features being poorly descriptive and having evolved convergently. In this work we report maximum parsimony and Bayesian phylogenetic analysis of a multigene dataset (nSSU rDNA, nLSU rDNA and β-tubulin gene) from sixty-seven taxa that include members of genera Ambrosiella, Raffaelea and Dryadomyces and a diverse set of ophiostomatoid relatives. We discuss the phylogenetic status of genus Ambrosiella and its relationships with representatives of Ophiostomatales teleomorph and anamorph genera. Our analysis shows that ten of the thirteen species that had been assigned to the genus Ambrosiella are related to the teleomorph genera Grosmannia or Ophiostoma, within the Ophiostomatales. The multigene analysis and expanded taxon samplings provide a higher resolution for the species phylogeny and clarify detailed relationships between Ambrosiella associates of ambrosia and bark beetles and the closely related species of genera Raffaelea and Dryadomyces. We discuss difficulties in using the morphology of conidiophores and the mode of conidiogenesis to re-define the phylogenetic classification of Ambrosiella species. Finally, we report a correlation between the molecular classification of Ophiostomatales-related species of Ambrosiella and Raffaelea and their ecological niches.

Fingerprinting of Penicillium crustosum strains was performed using different phenotypic characteristics. Seven strains of this extremely homogenous species were selected; of these, five originated from geographical locations characterized by low temperatures, and one from a location with a low water activity. Principal component analysis (PCA) was performed using micromorphological data, temperature- and water-dependent growth rates, and extrolite profiles obtained by HPLC analysis. The micromorphological data were less informative, while the growth-rate data were informative only if the strains investigated already showed slight adaptations to the selected external parameter. In contrast, PCA analyses of the extrolite data showed groupings of the strains according to their origins and known physiological differences. These groupings are in full agreement with the clustering obtained by previous amplified fragment length polymorphism (AFLP) study. We thus demonstrate here for the first time that combined qualitative and quantitative extrolite profiles can be used as a tool for phenotypic fingerprinting, to complement, or replace, molecular fingerprinting techniques.

Recent DNA sequence analyses indicated that Nigrosabulum globosum is a cleistothecial representative of the Bionectriaceae in the Hypocreales, but morphological characters supporting this relationship are unknown. Using light and electron microscopy we followed the development of the ascomata of this species, from the formation of gametangia through to the development of mature ascospores, and observed a series of characters that confirmed its hypocrealean affinities. These included the formation of a gel-filled centrum during early stages of ascoma development, the subsequent appearance of hyaline peridial tissue enclosed within a layer we interpret as representing a melanized uniloculate stroma, apically derived paraphyses, and an ascogenous system that gives rise to asci that were both cylindrical to clavate and globose. Ascospores, previously reported to be smooth, were ornamented with a honeycomb-like reticulum and were able to germinate within the ascoma. The carbonaceous outer (stromatic) walls of the mature, grit-like cleistothecia indicate possible resistance to UV radiation and desiccation. Furthermore, the complement of germinated ascospores would enable mature ascomata to function as propagules that could quickly initiate new growth when transferred to fresh substrate. Our reexamination of N. globosum also provides data that support the hypothesized close relationship with other bionectriaceous, cleistothecial coprophiles, i.e., species of Hapsidospora, and Bulbithecium in particular.

Lacazia loboi is a geographically restricted, uncultivated fungal pathogen of humans and dolphins. Previous investigations using 18S small unit rDNA, chitin synthase 2 and gp43 DNA sequences positioned L. loboi as a close relative of Paracoccidioides brasiliensis. However, given the few individuals of L. loboi studied and the high degree of genetic variation observed in P. brasiliensis, the existence of L. loboi as an independent species has been questioned. To investigate the phylogenetic position of this species, we conducted a phylogenetic analysis using 20 L. loboi collections (L. loboi was obtained from proven cases of lacaziosis and 14 collections were maintained in mice, the others were analyzed from DNA taken directly from infected human tissue.). L. loboi DNA sequence was compared to that from 17 P. brasiliensis strains that represented the known variation in this species, and outgroup taxa in the Onygenales (Ajellomyces and Coccidioides species). Our analyses used DNA sequence from ITS rRNA, and partial coding sequences of chitin synthase 4, ADP-ribosylation factor, and gp43. Nucleotide variation among strains of L. loboi was minor but numerous nucleotide mismatches and multiple gaps were found for these gene regions among members in the Ajellomycetaceae, including P. brasiliensis. Phylogenies inferred using neighbor-joining, maximum parsimony and Bayesian analyses showed no significant conflict and depicted L. loboi as a well-supported, monophyletic group that was sister to the Paracoccidioides clade. These results argue for maintaining L. loboi as a taxon independent from Paracoccidioides within the Ajellomycetaceae.

Microsclerotia (MS), overwintering structures produced by many plant pathogenic fungi, have not been described for Metarhizium anisopliae. Three strains of M. anisopliae – F52, TM109, and MA1200 – formed MS in shake flask cultures using media with varying carbon concentrations and carbon-to-nitrogen (C:N) ratios. Under the conditions of this study, all strains produced MS, compact hyphal aggregates that become pigmented with culture age, in addition to more typical blastospores and mycelia. While all strains formed desiccation tolerant MS, highest concentrations (2.7–2.9 × 10⁸ L⁻¹ liquid medium) were produced in rich media with C:N ratios of 30:1 and 50:1 by strain F52. All three strains of M. anisopliae produced similar biomass concentrations when media and growth time were compared. Strain MA1200 produced higher concentrations of blastospores than the other two strains of M. anisopliae with highest blastospore concentrations (1.6 and 4.2 × 10⁸ blastospores ml⁻¹ on days 4 and 8, respectively) in media with the highest carbon and nitrogen concentrations. Microsclerotial preparations of M. anisopliae containing diatomaceous earth survived air-drying (to <5 % moisture) with no significant loss in viability. Rehydration and incubation of air-dried MS granules on water agar plates resulted in hyphal germination and sporogenic germination to produce high concentrations of conidia. Bioassays using soil-incorporated, air-dried MS preparations resulted in significant infection and mortality in larvae of the sugar beet root maggot, Tetanops myopaeformis. This is the first report of the production of sclerotial bodies by M. anisopliae and provides a novel approach for the control of soil-dwelling insects with this entomopathogenic fungus.

The genes of the mitochondrial and cytosolic malate dehydrogenase (mMDH and cMDH) of Phytophthora infestans were cloned and overexpressed in Escherichia coli as active enzymes. The catalytic properties of these proteins were determined: both enzymes have a similar specific activity. In addition, the natural mitochondrial isoenzyme was semi-purified from mycelia and its catalytic properties determined: the recombinant mitochondrial isoform behaved as the natural enzyme. A phylogenetic analysis indicated that mMDH, present in all stramenopiles studied, can be useful to study the relationships between these organisms. MDH with the conserved domain MDH_cytoplasmic_cytosolic is absent in some stramenopiles as well as in fungi. This enzyme seems to be less related within the stramenopile group. The Phytophthora cMDHs have an insertion of six amino acids that is also present in the stramenopile cMDHs studied, with the exception of Thalassiosira pseudonana cMDH, and is absent in other known eukaryotic cMDHs.

A combined ITS and β-tubulin gene phylogeny has revealed new species of Hypocrella and Aschersonia related to the type species Hypocrella discoidea from natural forest in Thailand. As a result, Hypocrella calendulina and Hypocrella luteola are named as new species with Aschersonia sensu stricto anamorphs for specimens previously identified as Hypocrella discoidea sensu Petch. Hypocrella siamensis and Aschersonia minutispora are described as new species, both exhibiting brown stromata, with the former producing whole ascospores.