Recovery of growth of Hyphochytrium catenoides after exposure to environmental stress

ABSTRACT. The survival of an isolate of Hyphochytrium catenoides collected from soil in the Blue Mountains in eastern New South Wales, Australia, was tested under extreme conditions in the laboratory. This isolate recovered growth after being subjected to drying on filter paper, to heat while desiccated, to hypersalinity, to strict anaerobic conditions, to freezing temperatures, and to a short period in solutions at pH 2.8–11.2. The capacity to survive under these conditions in the laboratory suggests adaptation to fluctuating conditions in the soil. The partial DNA sequence of the 28S ribosomal RNA gene in the isolate from New South Wales was 98% similar to that in an isolate from Arizona with a similar morphology.     

The incidence of fungal spores in the ambient air and inside homes: Evidence from London

Little research has been carried out in London concerning fungal spore prevalence yet this information may help to elucidate geographical patterns of asthma and hay fever. Although many types of spore reach peak concentrations outdoors in late-summer, the incidences in the indoor environment may be more important through the winter because of heating and poor ventilation. Daily average concentrations of fungal spores in the ambient atmosphere were monitored with a Burkard volumetric spore trap on an exposed roof in North London from autumn 1991 until the summer of 1992. Indoor spore measurements were taken in 19 homes in the vicinity through the winter months, both by direct air sampling using a portable Burkard sampler and by dust culture. Trends in the occurrence and concentrations of fungal spores indoors and outdoors were examined. Relationships between the abundance of selected allergenic fungi and features of the houses were analysed including age of dwelling, dampness, cleanliness and presence of pets.Aspergillus andPenicillium were the most frequently occurring spore types in the homes. Overall, high spore incidence was associated with dampness and dust accumulation. The outdoor spore samples revealed generally low concentrations through the winter until March when concentrations of many types includingCladosporium, Epicoccum andAlternaria increased in abundance in response to the warmer weather. Even during the late-spring and early-summer, concentrations of most fungal spores were notably below those reported for rural sites.     

Antimicrobial fungal endophytes from the botanical medicine goldenseal (Hydrastis canadensis)

The potential of fungal endophytes to alter or contribute to plant chemistry and biology has been the topic of a great deal of recent interest. For plants that are used medicinally, it has been proposed that endophytes might play an important role in biological activity. With this study, we sought to identify antimicrobial fungal endophytes from the medicinal plant goldenseal (Hydrastis canadensis L., Ranunculaceae), a plant used in traditional medicine to treat infection. A total of 23 fungal cultures were obtained from surface-sterilized samples of H. canadensis roots, leaves and seeds. Eleven secondary metabolites were isolated from these fungal endophytes, five of which had reported antimicrobial activity. Hydrastis canadensis plant material was then analyzed for the presence of fungal metabolites using liquid chromatography coupled to high resolving power mass spectrometry. The antimicrobial compound alternariol monomethyl ether was detected both as a metabolite of the fungal endophyte Alternaria spp. isolated from H. canadensis seeds, and as a component of an extract from the H. canadensis seed material. Notably, fungi of the Alternaria genus were isolated from three separate accessions of H. canadensis plant material collected in a time period spanning 5 years. The concentration of alternariol monomethyl ether (991 mg/kg in dry seed material) was in a similar range to that previously reported for metabolites of ecologically important fungal endophytes. The seed extracts themselves, however, did not possess antimicrobial activity.     

Aerobiological study of fungal spores from Palencia (Spain)

A study of the concentration of fungal spores has been carried out in the atmosphere of Palencia town (NW Spain) during 1992. The volumetric method of filtration has been used. Half of the daily filter sample has been cultivated in Czapecdox-agar or Sabouraud-agar for the identification of fungal colonies, and the other half has been examined by optical microscopy. Several colonies belonging to 26 genera have been identified. Deuteromycetes (54%) and Zigomycetes (28%) are assembled in four genera, and Bacteria and Actynomycetes (18%) in three genera. The greatest concentrations occur forAspergillus (23%),Mucor (25%), followed byPenicillium (16%). The greatest diversity and abundance of fungal spores are found in September–December. The viable colonies are more abundant in Czapedox-agar culture, whereas Bacteria were more frequently found in Sabouraud medium.     

The rpb2 gene represents a viable alternative molecular marker for the analysis of environmental fungal communities

Although the commonly used internal transcribed spacer region of rDNA (ITS) is well suited for taxonomic identification of fungi, the information on the relative abundance of taxa and diversity is negatively affected by the multicopy nature of rDNA and the existence of ITS paralogues. Moreover, due to high variability, ITS sequences cannot be used for phylogenetic analyses of unrelated taxa. The part of single‐copy gene encoding the second largest subunit of RNA polymerase II (rpb2) was thus compared with first spacer of ITS as an alternative marker for the analysis of fungal communities in spruce forest topsoil, and their applicability was tested on a comprehensive mock community. In soil, rpb2 exhibited broad taxonomic coverage of the entire fungal tree of life including basal fungal lineages. The gene exhibited sufficient variation for the use in phylogenetic analyses and taxonomic assignments, although it amplifies also paralogues. The fungal taxon spectra obtained with rbp2 region and ITS1 corresponded, but sequence abundance differed widely, especially in the basal lineages. The proportions of OTU counts and read counts of major fungal groups were close to the reality when rpb2 was used as a molecular marker while they were strongly biased towards the Basidiomycota when using the ITS primers ITS1/ITS4. Although the taxonomic placement of rbp2 sequences is currently more difficult than that of the ITS sequences, its discriminative power, quantitative representation of community composition and suitability for phylogenetic analyses represent significant advantages.     

New diplosporin and agistatine derivatives produced by the fungal endophyte Xylaria sp. isolated from Vitis labrusca

A Xylaria sp. was isolated as an endophyte from a surface-sterilized Concord grape leaf (Vitis labrusca). Dereplication and LC–MS analysis of the filtrate extracts identified two new structures, compound 1, 13-O-methyl-(5R) diplosporin, and 2 a new agistatine. Additionally, five known compounds 3–7 including an agistatine, coriloxin, (5R)-diplosporin, and two mellein derivatives were also isolated. This is the first report of these structurally-related metabolites isolated from the same fungus, suggesting they share a related biosynthesis. Metabolites were isolated using liquid chromatography-solid phase extraction (LC-SPE) and semi-preparative HPLC. Structures were elucidated on the basis of 1D and 2D NMR analysis, HRMS measurements and X-ray structural analysis for compound 1.     

Expression of the gene encoding the PR-like protein PRms in germinating maize embryos

Summary The PRms protein is a pathogenesis-related (PR)-like protein whose mRNA accumulates during germination of maize seeds. Expression of the PRms gene is induced after infection of maize seeds with the fungus Fusarium moniliforme. To further our investigations on the expression of the PRms gene we examined the accumulation of PRms mRNA in different tissues of maize seedlings infected with E. moniliforme and studied the effect of fungal elicitors, the mycotoxin moniliformin, the hormone gibberellic acid, and specific chemical agents. Our results indicate that fungal infection, and treatment either with fungal elicitors or with moniliformin, a mycotoxin produced by F. monilforme, increase the steady-state level of PRms mRNA. PRms mRNA accumulation is also stimulated by the application of the hormone gibberellic acid or by treatment with silver nitrate, whereas acetylsalicylic acid has no effect. In situ RNA hybridization in isolated germinating embryo sections demonstrates that the PRms gene is expressed in the scutellum, particularly in a group of inner cells, and in the epithelium lying at the interface of the scutellum and the endosperm. The pattern of expression of the PRms gene closely resembles that found for hydrolytic enzymes, being confined to the scutellum and the aleurone layer of the germinating maize seed. Our results suggest that the PRms protein has a function during the normal process of seed germination that has become adapted to serve among the defence mechanisms induced in response to pathogens during maize seed germination.     

Isolation of thermophilic fungal strains producing oxido-reductase and hydrolase enzymes from various Tunisian biotopes

The present study surveys 37 thermophilic fungal strains, that were isolated from various Tunisian biotopes such as litter, husk and compost, for their involvement in lignin degradation activities. Oxido-reductase and hydrolase activities were screened. Oxido-reductase activities, such as Extracellular Oxidase, Laccase, Tyrosinase and Peroxidase, were tested. Hydrolase activities, namely Lipase, Protease, Amylase and Cellulase, were also revealed. Strain ST26, isolated from locally made compost, and showed an important laccase activity with ABTS and DMP, was selected. Laccase activity of strain ST26 was 1575 U/l in liquid media. This strain was identified and was belonging to Scytalidium genus and more precisely to the specie Scytalidium thermophilum using 5.8S rRNA gene sequencing analysis.     

Climate-related variation of the human nasal cavity

The nasal cavity is essential for humidifying and warming the air before it reaches the sensitive lungs. Because humans inhabit environments that can be seen as extreme from the perspective of respiratory function, nasal cavity shape is expected to show climatic adaptation. This study examines the relationship between modern human variation in the morphology of the nasal cavity and the climatic factors of temperature and vapor pressure, and tests the hypothesis that within increasingly demanding environments (colder and drier), nasal cavities will show features that enhance turbulence and air-wall contact to improve conditioning of the air. We use three-dimensional geometric morphometrics methods and multivariate statistics to model and analyze the shape of the bony nasal cavity of 10 modern human population samples from five climatic groups. We report significant correlations between nasal cavity shape and climatic variables of both temperature and humidity. Variation in nasal cavity shape is correlated with a cline from cold-dry climates to hot-humid climates, with a separate temperature and vapor pressure effect. The bony nasal cavity appears mostly associated with temperature, and the nasopharynx with humidity. The observed climate-related shape changes are functionally consistent with an increase in contact between air and mucosal tissue in cold-dry climates through greater turbulence during inspiration and a higher surface-to-volume ratio in the upper nasal cavity.     

The distribution of the NADPH regenerating mannitol cycle among fungal species

The mannitol cycle is an important NADPH regenerating system in Alternaria alternata. The cycle is built up of the following enzymes: mannitol 1-phosphate dehydrogenase, mannitol 1-phosphatase, mannitol dehydrogenase and hexokinase. The net reaction of one cycle turn is: NADH+NADP⁺+ATP NAD⁺+NADPH+ADP+P_i. The enzymes needed for an operating cycle were found in Aspergillus, Botrytis, Penicillium, Pyricularia, Trichothecium, Cladosporium and Thermomyces all genera belonging to Fungi Imperfecti. The only genus of this class lacking the cycle was Candida. No genera from the classes Basidiomycetes and Phycomycetes showed any mannitol 1-phosphate dehydrogenase or mannitol 1-phosphatase activities. The genera investigated, belonging to Ascomycetes, Gibberella, Ceratocystis and Neurospora all lacked mannitol 1-phosphate dehydrogenase. It was concluded that the mannitol cycle is an important and widespread pathway for NADH oxidation and NADP⁺ reduction in the organisms belonging to the class Fungi Imperfecti.     

Diversity and ecology of fungal assemblages present in lake sediments at Clearwater Mesa,James Ross Island,Antarctica, assessed using metabarcoding of environmental DNA

We detected the fungal assemblages present in lake sediments on James Ross Island, Antarctica, using DNA metabarcoding. A total of 132 amplicon sequence variants (ASVs) were assigned, dominated by taxa of the phyla Ascomycota, Basidiomycota, Mortierellomycota and Mucoromycota. The less common phyla Chytridiomycota, Rozellomycota, Monoblepharomycota, Basidiobolomycota, Aphelidiomycota and the fungus-like Straminopila were also detected. Fungal sp. 1, Fungal sp. 2, Spizellomycetales sp. 1, Rozellomycotina sp. 1, Talaromyces rubicundus and Betamyces sp. dominated the assemblages. In general, the assemblages displayed high diversity and richness, and moderate dominance. Saprophytic, pathogenic and symbiotic fungi were detected. The metabarcoding data indicated that Antarctic lakes may represent a hotspot of fungal diversity in Antarctica. The sediments of these lakes may accumulate different fungal fragments and active fungal mycelia and their propagules, deposited over long periods of time. Lakes in the Antarctic Peninsula region are sensitive environments threatened by the effects of regional climatic changes. The abundance of sequences of little-known Rozellomycota and Chytridiomycota (Spizellomycetales) taxa in these ecosystems highlights the need for further studies to identify if they are metabolically active in the sediments and whether they have potentially pathogenic capabilities.     

From fundamental biology to the search for innovation: The story of fungal extracellular vesicles

Fungal extracellular vesicles (EVs) have attracted increased attention in recent years. Originated from a serendipitous discovery, the initial observation of fungal EVs resulted in a set of data repetitively rejected by several scientific journals, which raised questions about their authenticity. However, after the most fundamental experimental issues related to their observation were addressed, fungal EVs were characterized in dozens of species and became an emerging field. In this essay, we will discuss these fundamental findings and the potential of fungal EVs for the development of vaccines and antifungals.     

Molecular characterization of fungal community dynamics in the initial stages of composting

Composting relies on a complex network of bacteria and fungi to process crude organic material. Although it is known that these organisms drive dynamic changes in temperature and pH, little is known about the temporal dynamics of fungal populations during the rise to thermophilic conditions. This study employed F-ARISA (fungal-automated rRNA intergenic spacer analysis) and 18S rRNA gene cloning and sequencing to examine changes in community structure during this period. Sequencing of the 18S rRNA portion of cloned F-ARISA products revealed the presence of four distinct fungal genera including Backusella sp., Mucoraceae, Geotrichum sp. and the yeast Pichia sp. Based on the presence and absence of these ARISA operational taxonomic units (A-OTUs), we observed a shift in fungal community structure between 48 and 60 h. This change in community structure preceded a rise in pH and coincided with an increase in temperature. Clone libraries constructed using fungi-specific 18S rRNA primers contained sequences similar to several other fungal genera including Penicillium sp., Aspergillus sp., Hamigera sp., Neurospora sp. and the yeast Candida sp. While the fungal species richness was relatively low at any time point, the community structure was dynamic and paralleled changes in bacterial community structure.     

Gene exchange between two divergent species of the fungal human pathogen,Coccidioides

The fungal genus Coccidioides is composed of two species, Coccidioides immitis and Coccidioides posadasii. These two species are the causal agents of coccidioidomycosis, a pulmonary disease also known as valley fever. The two species are thought to have shared genetic material due to gene exchange in spite of their long divergence. To quantify the magnitude of shared ancestry between them, we analyzed the genomes of a population sample from each species. Next, we inferred what is the expected size of shared haplotypes that might be inherited from the last common ancestor of the two species and find a cutoff to find what haplotypes have conclusively been exchanged between species. Finally, we precisely identified the breakpoints of the haplotypes that have crossed the species boundary and measure the allele frequency of each introgression in this sample. We find that introgressions are not uniformly distributed across the genome. Most, but not all, of the introgressions segregate at low frequency. Our results show that divergent species can share alleles, that species boundaries can be porous, and highlight the need for a systematic exploration of gene exchange in fungal species.     

Effects of boron-containing compounds in the fungal kingdom

BackgroundThe number of known boron-containing compounds (BCCs) is increasing due to their identification in nature and innovative synthesis procedures. Their effects on the fungal kingdom are interesting, and some of their mechanisms of action have recently been elucidated.MethodsIn this review, scientific reports from relevant chemistry and biomedical databases were collected and analyzed.ResultsIt is notable that several BCC actions in fungi induce social and economic benefits for humans. In fact, boric acid was traditionally used for multiple purposes, but some novel synthetic BCCs are effective antifungal agents, particularly in their action against pathogen species, and some were recently approved for use in humans. Moreover, most reports testing BCCs in fungal species suggest a limiting effect of these compounds on some vital reactions.ConclusionsNew BCCs have been synthesized and tested for innovative technological and biomedical emerging applications, and new interest is developing for discovering new strategic compounds that can act as environmental or wood protectors, as well as antimycotic agents that let us improve food acquisition and control some human infections.     

Caspofungin reduces the incidence of fungal contamination in cell culture

Fungal contamination is a major problem in cell culture, and the antifungal compounds currently in use can affect cultured cells. Echinocandins are antifungal drugs that inhibit fungal cell wall synthesis by targeting an enzyme that has no counterpart in mammalian cells. We evaluated whether the echinocandin caspofungin affected the growth or morphology of six murine cell lines (a macrophage-like cell line (J774.16) and five hybridoma lines), or primary human endothelial cells. The antifungal did not influence cellular characteristics at concentrations less than 512 μg/ml, while effectively reducing the incidence of fungal contamination. Also, caspofungin did not affect the production of antibody by hybridoma cells, or alter the cytokine production of J774.16 cells, although modest increases in IL-4 and IFN-γ occurred upon LPS stimulation. Hence, echinocandins appear to be relatively non-toxic, and protect against fungal contamination in cell culture.     

Evaluation of different methods for the extraction of DNA from fungal conidia by quantitative competitive PCR analysis.

Five different DNA extraction methods were evaluated for their effectiveness in recovering PCR templates from the conidia of a series of fungal species often encountered in indoor air. The test organisms were Aspergillus versicolor, Penicillium chrysogenum, Stachybotrys chartarum, Cladosporium herbarum and Alternaria alternata. The extraction methods differed in their use of different cell lysis procedures. These included grinding in liquid nitrogen, grinding at ambient temperature, sonication, glass bead milling and freeze-thawing. DNA purification and recovery from the lysates were performed using a commercially available system based on the selective binding of nucleic acids to glass milk. A simple quantitative competitive polymerase chain reaction (QC-PCR) assay was developed for use in determining copy numbers of the internal transcribed spacer (ITS) regions of the ribosomal RNA operon (rDNA) in the total DNA extracts. These quantitative analyses demonstrated that the method using glass bead milling was most effective in recovering PCR templates from each of the different types of conidia both in terms of absolute copy numbers recovered and also in terms of lowest extract to extract variability. Calculations of average template copy yield per conidium in this study indicate that the bead milling method is sufficient to support the detection of less than ten conidia of each of the different organisms in a PCR assay.     

Evidence of fungal decay in petrified legume wood from the Neogene of the Bengal Basin,India

Silicified fossil legume woods of Cynometroxylon Chowdhury & Ghosh collected from the Neogene (late Miocene) sediments of the Bengal Basin, eastern India, exhibit fungal decay seldom found in the fossil record. The wood possesses numerous perforate areas on the surface that seem to be the result of extensive fungal activity. In transverse section, the decayed areas (pockets) appear irregular to ellipsoidal in outline; in longitudinal section these areas of disrupted tissue are somewhat spindle-shaped. Individual pockets are randomly scattered throughout the secondary xylem or are restricted to a narrow zone. The aforesaid patterns of decay in fossil wood show similarities with that of white rot decay commonly produced by higher fungi, specifically basidiomycetes and ascomycetes. The host fossil wood harbors abundant ramifying and septate fungal hyphae with knob like swellings similar to pseudoclamps in basidiomycetes, and three-celled conidia-like reproductive structures. This record expands our current knowledge of wood decaying fungi-host plant interaction in the Neogene tropical forests of Peninsular India.     

Relationships of fungal spore concentrations in the air and meteorological factors

High concentrations of airborne fungal spores are associated with human health concerns. Environmental variables, such as temperature and moisture, can influence growth and reproduction in fungi and airborne spore concentrations can fluctuate seasonally. However, we do not understand how long-term changes in climate affect fungal abundance in the air. Here, we sampled annually (at peak season, in September, over a 20-yr period) for airborne fungal spores in two North American cities (New York and Toronto), and related fungal abundance to local variation in climate. We found that at both locations, the total precipitation during the 2- month period prior to sampling (Jul.–Aug.) was negatively related to observed fungal spore concentrations. Considering that climate predictions for these two regions indicate an increase in drought events in summer, we expect airborne fungal concentrations to increase in future years, potentially exacerbating human health concerns.     

Damage and recovery from UV-B exposure in conidia of the entomopathogens Verticillium lecanii and Aphanocladium album

We evaluated the effects of exposure to doses supplied at an environmentally realistic intensity of UV-B radiation (800 mW m(-2) weighted irradiance) on the culturability and germination of selected strains of the entomopathogenic Hyphomycetes Verticillium lecanii and Aphanocladium album. Increased UV-B exposure decreased relative percent culturability for all strains. Four hours of exposure to UV-B were sufficient to reduce the culturability close to zero. The LT(50) (50% lethal time) ranged from 120 ± 5 min for the V. lecanii strain ARSEF 6430 to 86 ± 14 min for the A. album strain ARSEF 6433. A strong delay in the germination of surviving conidia was observed. To determine the occurrence of photoreactivation in these two genera, we evaluated the effect of exposure to visible light after exposure to UV-B radiation. There was no significant difference in relative culturability between conidia exposed to visible light after UV-B exposure compared to those incubated in the dark after UV-B exposure. This indicates that photoreactivation, if it occurs, must have limited importance in the repair of the damage induced by UV-B radiation in these two genera.