Aspergillus Fischeri Research Articles

Strain heterogeneity in a non-pathogenic Aspergillus fungus highlights factors associated with virulence

Fungal pathogens exhibit extensive strain heterogeneity, including variation in virulence. Whether closely related non-pathogenic species also exhibit strain heterogeneity remains unknown. Here, we comprehensively characterized the pathogenic potentials (i.e., the ability to cause morbidity and mortality) of 16 diverse strains of Aspergillus fischeri, a non-pathogenic close relative of the major pathogen Aspergillus fumigatus. In vitro immune response assays and in vivo virulence assays using a mouse model of pulmonary aspergillosis showed that A. fischeri strains varied widely in their pathogenic potential. Furthermore, pangenome analyses suggest that A. fischeri genomic and phenotypic diversity is even greater. Genomic, transcriptomic, and metabolic profiling identified several pathways and secondary metabolites associated with variation in virulence. Notably, strain virulence was associated with the simultaneous presence of the secondary metabolites hexadehydroastechrome and gliotoxin. We submit that examining the pathogenic potentials of non-pathogenic close relatives is key for understanding the origins of fungal pathogenicity.

Aspergillus fumigatus conidial surface-associated proteome reveals factors for fungal evasion and host immunity modulation.

Aspergillus fumigatus causes aspergillosis and relies on asexual spores (conidia) for initiating host infection. There is scarce information about A. fumigatus proteins involved in fungal evasion and host immunity modulation. Here we analysed the conidial surface proteome of A. fumigatus, two closely related non-pathogenic species, Aspergillus fischeri and Aspergillus oerlinghausenensis, as well as pathogenic Aspergillus lentulus, to identify such proteins. After identifying 62 proteins exclusively detected on the A. fumigatus conidial surface, we assessed null mutants for 42 genes encoding these proteins. Deletion of 33 of these genes altered susceptibility to macrophage, epithelial cells and cytokine production. Notably, a gene that encodes a putative glycosylasparaginase, modulating levels of the host proinflammatory cytokine IL-1β, is important for infection in an immunocompetent murine model of fungal disease. These results suggest that A. fumigatus conidial surface proteins are important for evasion and modulation of the immune response at the onset of fungal infection.

Evaluation of multi-heavy metal tolerance traits of soil-borne fungi for simultaneous removal of hazardous metals.

The demand for environment-friendly cleanup techniques has arisen due to an increase in environmental pollutants. Fungi is the most prevalent and effective class of heavy metal-resistant microorganisms with the ability to leach metals. The objective of the present study was to isolate the fungi from the agricultural soil of Kashmir valley, investigate their multi-metal tolerance to heavy metals and evaluate the metal uptake capacities of the resistant fungi. The fungi were isolated and identified on the basis of morphological and molecular approach (ITS1 and ITS4). The tolerance limits of the isolated fungal strains to various doses of lead (Pb), cadmium (Cd), zinc (Zn), chromium (Cr), copper (Cu), nickel (Ni), and cobalt (Co) was evaluated. Five fungal strains, Aspergillus niger, Fusarium oxysporum, Fusarium verticillioides, Aspergillus fischeri, Epicoccum mackenziei were isolated from the soil samples. To the best of our knowledge, this is the first report on the study of metal resistance of Aspergillus fischeri and Epicoccum mackenziei. Among the identified fungal species, Aspergillus niger and Fusarium oxysporum were found to be most tolerant with a minimum inhibitory concentration (MIC) of 600 ppm against Cu and Cr respectively. Results indicated removal of considerable amount of heavy metals by some of the fungi. The highest metal uptake of 8.31mg/g was found in Fusarium verticillioides for Zn. Surprisingly, these fungal strains demonstrated resistance to metal concentrations above the levels that are universally acceptable for polluted soils, and hence prove to be appealing contenders for use as bioremediation agents for cleaning up heavy metal-polluted environments.

Hydroxytakakiamide and Other Constituents from a Marine Sponge-Associated Fungus Aspergillus fischeri MMERU23, and Antinociceptive Activity of Ergosterol Acetate, Acetylaszonalenin and Helvolic Acid.

An unreported prenylated indole derivative hydroxytakakiamide (4) was isolated, together with the previously described ergosterol (1), ergosterol acetate (2), and (3R)-3-(1H-indol-3-ylmethyl)-3, 4-dihydro-1H-1,4-benzodiazepine-2,5-dione (3), from the column fractions of the crude ethyl acetate extract of the culture of a marine sponge-associated fungus, Aspergillus fischeri MMERU 23. The structure of 4 was elucidated by the interpretation of 1D and 2D NMR spectral data and high-resolution mass spectrum. The absolute configuration of the stereogenic carbon in 3 was proposed to be the same as those of the co-occurring congeners on the basis of their biogenetic consideration and was supported by the comparison of its sign of optical rotation with those of its steroisomers. The crude ethyl acetate extract and 2 were evaluated, together with acetylaszonalenin (5) and helvolic acid (6), which were previously isolated from the same extract, for the in vivo antinociceptive activity in the mice model. The crude ethyl acetate extract exhibited antinociceptive activity in the acetic acid-induced writhing and formalin tests, while 2, 5, and 6 displayed the effects in the late phase of the formalin test. On the other hand, neither the crude ethyl acetate extract nor 2, 5, and 6 affected the motor performance of mice in both open-field and rotarod tests. Additionally, docking studies of 2, 5, and 6 were performed with 5-lipoxygenase (5-LOX) and phosphodiesterase (PDE) enzymes, PDE4 and PDE7, which are directly related to pain and inflammatory processes. Molecular docking showed that 6 has low affinity energy to PDE4 and PDE7 targets while retaining high affinity to 5-LOX. On the other hand, while 2 did not display any hydrogen bond interactions in any of its complexes, it achieved overall better energy values than 6 on the three antinociceptive targets. On the other hand, 5 has the best energy profile of all the docked compounds and was able to reproduce the crystallographic interactions of the 5-LOX complex.

Superheated steam effectively inactivates diverse microbial targets despite mediating effects from food matrices in bench-scale assessments

Sanitation in dry food processing environments is challenging due to the exclusion of water. Superheated steam (SHS) is a novel sanitation technique that utilizes high temperature steam to inactivate microorganisms. The high sensible heat of SHS prevents condensation on surfaces. Here we evaluated SHS thermal inactivation of various vegetative and spore forming bacteria and fungi and determined the effect of food matrix composition on SHS efficacy. Capillary tubes with vegetative cells (Salmonella, E. coli O157:H7, Listeria monocytogenes, or Enterococcus faecium), Aspergillus fischeri ascospores, or B. cereus spores (100 μL) were SHS treated at 135 ± 1 °C for 1 or 2 s. After 1 s, SHS achieved a reduction of 10.91 ± 0.63 log10 CFU/mL for vegetative cells, 2.09 ± 0.58 log10 ascospores/mL for A. fischeri, and 0.21 ± 0.10 log10 spores/mL for B. cereus. SHS treatment achieved significant reductions in vegetative cells and fungal ascospores (p < 0.05), however B. cereus spores were not significantly reduced after 2 s and were determined to be the most resistant of the cell types evaluated. Consequently, peanut butter compositions (peanut powder, oil, and water) and milk powder (whole and nonfat) inoculated with B. cereus spores on aluminum foil coupons (2 × 3 × 0.5 cm) were tested. The D161°C values for B. cereus spores ranged from 46.53 ± 4.48 s (6 % fat, 55 % moisture, aw: 0.927) to 79.21 ± 14.87 s (43 % fat, 10 % moisture, aw: 0.771) for various peanut butter compositions. Whole milk powder had higher D161°C (34.38 ± 20.90 s) than nonfat milk powder (24.73 ± 6.78 s). SHS (135 ± 1 °C) rapidly (1 s) inactivated most common vegetative bacterial cells; however B. cereus spores were more heat resistant. B. cereus spore inactivation was significantly affected by product composition (p < 0.05). Compared to the log-linear model (R2 0.81–0.97), the Weibull model had better fit (R2 0.94–0.99). Finally, the ease of peanut butter removal from surfaces increased while the ease of non-fat dry milk removal decreased with the increasing SHS treatment duration. However, allergen residues were detectable on surfaces regardless of SHS treatment. The findings from this study can inform the development of pilot-scale research on SHS.

Textile Dye Decolorization Ability of Decaying Hardwood Associated Fungi

Random disposal of synthetic textile dyes has created severe damage to the environment. These dye effluents, even at very low concentrations, can be toxic, mutagenic and carcinogenic to various organisms. Complex chemical structures enable the textile dyes to remain stable and inert towards degradation in soil and water. Therefore, textile dye decolorization has gained special attention in the recent past. Biological means of dye decolorization have become one of the attractive decolorization methods. Fungi show a great potency in decolorizing a wide variety of dyes by secreting highly oxidative and nonspecific ligninolytic enzymes such as laccases. The main aim of the current study was to evaluate the dye decolorization abilities of selected fungal isolates associated with decaying hardwoods in Sri Lanka. A total of 10 wood decay fungal isolates were screened for the laccase production and lignin degradation using guaiacol and lignin powder amended media respectively. Phlebiopsis flavidoalba, Phanerochaete chrysosporium, P. pseudomagnoliae and two Schizophyllum commune strains showed both laccase production as well as lignin degradation abilities. Although unable to produce laccases, Fusarium pseudensiforme and Aspergillus fischeri showed lignin degradation ability. Azo Disperse Rubine Red, Indigo Carmine Blue and Disperse Black were selected as textile dyes. Three replicates from each isolate were incubated for 21 days in potato dextrose broth amended with each dye in two concentrations, and percentage reduction in absorbance at 610 nm (for the Indigo Carmine Blue dye) and 400 nm (for Azo Disperse Rubine Red and Disperse Black) were estimated. Dye introduced potato dextrose broth, without fungal isolates were used as controls. P. flavidoalba was the best in decolorizing Azo Disperse Rubine Red (25 mg/L) and Disperse Black (50 mg/L) dyes showing the reduction of absorbance values by 89% and 81% respectively. For the Indigo Carmine Blue dye, F. pseudensiforme showed the highest percent decolorization of 85% at 0.1 ml/L concentration. This is the first report of these organism's ability to decolorize industrial dyes. Based on the results it was evident that some of the hardwood decay fungi have industrial dye decolorization abilities where they can be effectively utilized in dye decolorization and in future bioremediation research as well.&#x0D; Keywords: Dye decolorization, Laccase, Wood decay, Fungi, Lignin&#x0D; Acknowledgement: Authors acknowledge the TWAS Research Grant 18-020 RG/BIO/AS_I, NSF Sri Lanka RG/2019//BT/03 and ICGEB/CRP/LKA/18-3

Cytotoxic polyketides from the deep-sea-derived fungus Aspergillus fischeri FS452

Six globoscin derivatives (1‒6) including two new ones fischerins A (1) and B (2) were isolated from the deep-sea-derived fungus Aspergillus fischeri FS452. Their structures were elucidated by comprehensive spectroscopic analysis and the absolute configurations were determined by the quantum chemical ECD calculations. The in vitro cytotoxicity assays indicated that fischerin B (2) exhibited potential activities against the four tested human cancer cell lines (SF-268, MCF-7, HepG-2 and A549) with the IC50 values in the range of 7–10 µM.

Thermal shift assays of marine-derived fungal metabolites from Aspergillus fischeri MMERU 23 against Leishmania major pteridine reductase 1 and molecular dynamics studies

Marine-derived fungi are a promising source of bioactive molecules, especially species from extreme habitats. Although several secondary metabolites such as meroterpenoids and alkaloids have been isolated from cultures of Aspergillus fischeri, obtained from terrestrial habitats, there is no report on compounds isolated from marine-derived strains. Many metabolites isolated from marine-derived fungi exhibited a myriad of biological activities. Marine natural products have shown to be an important source of bioactive compounds and can assist in the discovery of molecules with affinity against validated targets from exclusive strains of parasites of medical importance such as pteridine reductase 1 (PTR1), from Leishmania major, which is essential for cell growth. Leishmaniasis is responsible for approximately 65,000 annual deaths. Despite the mortality data, drugs available for the treatment of patients are insufficient and have moderate therapeutic efficacy in addition to serious adverse effects, which make the development of new drugs urgent. The previously described aszonalenin (ASL), aszonapyrone A (ASP), acetylaszonalenin (ACZ), and helvolic acid (HAC) were isolated from the ethyl acetate extract of the culture of a marine sponge-associated A. fischeri MMERU 23 and their affinities against PTR1 were determined by ThermoFluor®. Among the tested compounds, only ACZ showed dose-dependent affinity against PTR1. Moreover, complementary molecular dynamics studies (t = 100 000 ps) have showed that this molecule performs hydrogen bonds with key residues at the active site for more than 60% of the productive trajectory time. The results indicate that ACZ could be a promising PTR1 inhibitor and a potential candidate for development of antileishmanial drug. Communicated by Ramaswamy H. Sarma

Enzymatic pretreatment of algal biomass has different optimal conditions for biogas and bioethanol routes

Enzymatic pretreatment is emerging as an efficient tool for the extraction of biofuel precursors from algal biomass. However, yardsticks for end-use directed selection of optimal pretreatment conditions are not yet identified. The present study, for the first time, reveals different optimal conditions for algal biomass solubilization and sugar release. Algal biomass pretreatment optimization was carried out using the Taguchi method. Crude enzyme from Aspergillus fischeri was found effective for pretreatment of Chlorella pyrenoidosa. Maximum sugar yield (190 mg g−1 biomass) from algal biomass was observed at a substrate concentration of 4 g L-1, with a 5% enzyme load at temperature 60°C, pH 5.5, and shaking speed of 80 rpm. In contrast, maximum sCOD (1350 mg g−1 biomass) was obtained at 2 g L−1 substrate concentration with enzyme load of 20% v/v, at 60°C, pH 4, and shaking speed of 100 rpm. Hence, the first set of conditions would be more beneficial for bioethanol production. Whereas another set of conditions would improve the biofuel production that requires maximum solubilization of algal biomass, such as fermentative methane production. Overall, the present observations established that process conditions required for enzymatic pretreatment of algal biomass should be selected according to the desired biofuel type.

Molecular Characterization and Differentiation of Proteases Isolated from Different Aspergillus Fungal Species

A comparative molecular study of Aperigiullus protease using sequence of protease gene representative 25 different Aspergillus species (Aspergillus fumigatus, Aspergillus oryzae, Aspergillus flavus, Aspergillus novofumigatus, Aspergillus viridinutans, Aspergillus pseudotamarii, Aspergillus clavatus, Aspergillus sojae, Aspergillus fischeri, Aspergillus caelatus, Aspergillus novofumigatus, Aspergillus campestris, Aspergillus costaricaensis, Aspergillus candidus, Aspergillus neoniger, Aspergillus mulundensis, Aspergillus ibericus, Aspergillus niger, Aspergillus piperis, Aspergillus eucalypticola, Aspergillus vadensis, Aspergillus steynii, and Aspergillus lentulus) have been described for several properties. To summarise the Asperigillus protease correlation, alignment of multiple sequence and phylogenetic tree assembly were carried out. 59 Protease gene amino acid sequence used for the constructed phylogenetic tree that showed the specific protease clusters of several species of Aspergillus (Aspergillus oryzae, Aspergillus fumigatus, Aspergillus clavatus, Aspergillus niger, Aspergillus nidulans, Aspergillus viridinutans, Aspergillus flavus and Aspergillus fischeri). Protease gene amino acid sequences acquired from NCBI. The homology sequence level was done using amino acid sequence. Among these proteases, the distributions of the commonly observed motifs were analysed. Protease protein sequences indicate that the structure and enzymatic function are involved.

Diversity of soil culturable fungi in the tropical montane cloud forest of Veracruz, Mexico

Background: Cloud forest is one of the most threatened ecosystems in the world and more than half of its original area has been transformed for other land uses. Consequently, macro- and microorganisms of this ecosystem have likely undergone changes.&#x0D; Objective: To analyze the diversity of saprobic filamentous soil cultured fungi in four cloud forest fragments and evaluate the similarity in species composition among fragments.&#x0D; Methods: To detect and isolate soil microfungi, the soil particle filtration technique was used. Emerging colonies were transferred to a culture medium for subsequent quantification and identification. For each species, permanent and semi-permanent slide preparations were made, and taxonomic identification was performed based on morphological features.&#x0D; Results and conclusions: From 20 soil samples and 2000 inoculated particles, 233 species were distinguished. The most common species were Myrmecridium schulzeri, Pestalotiopsis maculans, Trichoderma atroviride, Virgaria nigra, Trichoderma cremeum, Fusarium solani, Cordana terrestris, Aspergillus fischeri, and Penicillium olsoni. The most abundant species were Talaromyces flavus and Pestalotiopsis maculans. All the forest fragments had a high richness, diversity, and evenness in addition to a high turnover and high number of exclusive species.

Optimization of Mycological Media Using Agro Waste for the Production of Antimicrobial Substance

Aim: This present study was conducted to optimize mycological media using agro waste for the production of antimicrobial substance.&#x0D; Place and Duration of Study: Agro waste (sugarcane and sweet potato, sugarcane and jack fruit) collected within Anambra state between February- August 2019.&#x0D; Methodology: Sugarcane and sweet potato (AMSSP), sugarcane and jack fruit (AMSJ) were peeled and the peels were air-dried and then ground into powdered form. 10 g each of the agro waste samples was weighed into 400 ml of distilled water in 1000 ml Erlenmeyer flask and allowed for 7 days, after which the mixture was filtered.&#x0D; Then 200 ml of the filtrate was used.&#x0D; The experimental conditions were optimized by using agro wastes (20/80 and 50/50 concentrations) as a culture medium, altering the temperature (30ºC and 37ºC), pH (5, 6, 7, 8, and 9), as well as the carbon and nitrogen source (glucose and NaNO3). The fungi used were Aspergillus niger, Aspergillus fischeri, Aspergillus aculeatus and Aspergillus fumigatus.&#x0D; Results: Various agro wastes medium AMSSP and AMSJ were formulated as mycological media and the growth and nutritional conditions were optimized to ascertain antimicrobial substance production using some fungal isolates. Based on different concentrations Aspergillus fumigatus showed a promising zone of inhibition on AMSSP at a concentration of 20/80 while in AMSJ the concentration the 50/50 showed a maximum zone of inhibition on Aspergillus fumigatus ascertaining the presence of antimicrobial substance. AMSSP was able to produce maximum antimicrobial substance when supplemented with 1.0% glucose, 1.0% NaNO3 at pH 7 and at temperature of 30 ± 2ºC.&#x0D; Conclusion: Agro wastes from AMSSP as well as from AMSJ contain nutrients that may support fungal growth. Maximum antimicrobial substance production is enhanced when supplemented with 1.0% of the carbon and nitrogen source at a pH of 7 and at a temperature of 30 ± 2ºC.

Variation Among Biosynthetic Gene Clusters, Secondary Metabolite Profiles, and Cards of Virulence Across Aspergillus Species.

Aspergillus fumigatus is a major human pathogen. In contrast, Aspergillus fischeri and the recently described Aspergillus oerlinghausenensis, the two species most closely related to A. fumigatus, are not known to be pathogenic. Some of the genetic determinants of virulence (or "cards of virulence") that A. fumigatus possesses are secondary metabolites that impair the host immune system, protect from host immune cell attacks, or acquire key nutrients. To examine whether secondary metabolism-associated cards of virulence vary between these species, we conducted extensive genomic and secondary metabolite profiling analyses of multiple A. fumigatus, one A. oerlinghausenensis, and multiple A. fischeri strains. We identified two cards of virulence (gliotoxin and fumitremorgin) shared by all three species and three cards of virulence (trypacidin, pseurotin, and fumagillin) that are variable. For example, we found that all species and strains examined biosynthesized gliotoxin, which is known to contribute to virulence, consistent with the conservation of the gliotoxin biosynthetic gene cluster (BGC) across genomes. For other secondary metabolites, such as fumitremorgin, a modulator of host biology, we found that all species produced the metabolite but that there was strain heterogeneity in its production within species. Finally, species differed in their biosynthesis of fumagillin and pseurotin, both contributors to host tissue damage during invasive aspergillosis. A. fumigatus biosynthesized fumagillin and pseurotin, while A. oerlinghausenensis biosynthesized fumagillin and A. fischeri biosynthesized neither. These biochemical differences were reflected in sequence divergence of the intertwined fumagillin/pseurotin BGCs across genomes. These results delineate the similarities and differences in secondary metabolism-associated cards of virulence between a major fungal pathogen and its nonpathogenic closest relatives, shedding light onto the genetic and phenotypic changes associated with the evolution of fungal pathogenicity.

Quantitative microbial spoilage risk assessment (QMSRA) of pasteurized strawberry purees by Aspergillus fischeri (teleomorph Neosartorya fischeri)

Aspergillus fischeri ascospores are known as potential spoilage microorganisms of pasteurized fruit products due to their high incidence in fruits, the ability to survive pasteurization and to grow in acidic conditions. This study aimed to develop a quantitative microbial spoilage risk assessment (QMSRA) model approach to estimate the spoilage risk of packaged strawberry purees due to A. fischeri under various scenarios regarding product formulation, processing and storage conditions. The development of the risk assessment comprised three steps: (1) initial contamination level of raw material by ascospores (N0), (2) inactivation of ascospores during thermal processing (Np) and (3) determination of the number of ascospores which are able to survive thermal processing and develop visible mycelia (D = 2 mm) during storage (Nf). Data of visible growth (tv, days) comprised distributions previously obtained as function of water activity (aw) (0.860–0.985), oxygen (0–21%), temperature (8–30 °C) and pasteurization (95–105 °C/15 s). The simulations were performed in triplicate with 100,000 iterations using the software R. The outcome “spoilage risk” was defined as the probability of having at least one ascospore (Nf) capable of forming visible colonies in 100 g-pack strawberry puree within the typical use-by dates. Overall, high probabilities of spoilage were estimated for purees pasteurized at milder treatments at 85 °C/15–60 s (67%) and 90 °C/15–60 s (≥40%) stored at ambient temperature (22 °C). The spoilage risk was only effectively reduced (0.02%) by increasing pasteurization conditions to 95 °C for at least 45 s. Moreover, the microbial stability of such purees, i.e., spoilage risk <0.001% (=less than 1 spoilage pack out of 105 produced units) was predicted to occur for purees treated at 100 °C/15 s or stored at chilled conditions (≤8 °C) or at strict anaerobic conditions or produced as concentrates (aw ≤ 0.860). Based on the outcomes obtained, a set of specifications for Heat-Resistant Moulds (HRMs) in raw material and pasteurized purees aimed to be used as an ingredient was suggested. Furthermore, the results can be used to support risk management decisions in identifying and quantifying the impact of possible interventions during formulation, processing and storage conditions of fruit purees to effectively reduce this risk.

Modeling the inactivation of Aspergillus fischeri and Paecilomyces niveus ascospores in apple juice by different ultraviolet light irradiances

The present work aimed to evaluate and to model the influence of UV-C light treatments with different irradiances (6.5, 13, 21, and 36 W/m2) on Aspergillus fischeri and Paecilomyces niveus ascospores inactivation in clarified apple juice. Approximately 5.0 and 6.0 log CFU/mL spores of P. niveus and A. fischeri, respectively, were suspended in 30 mL of clarified apple juice (pH 3.8, 12 ± 0.1°Brix) and exposed to UV-C light at different irradiances (as above) and exposure times (0 to 30 min). The first-order biphasic model was able to describe the experimental data with good statistical indices (RMSE = 0.296 and 0.308, R2 = 0.96 and 0.98, for P. niveus and A. fischeri respectively). At the highest irradiance level tested (36 W/m2), the UV-C light allowed the reduction of 5.7 and 4.2 log-cycles of A. fischeri and P. niveus ascospores, respectively, in approximately 10 min. P. niveus was the most UV-C resistant mould. The results showed that, to a defined UV-C fluence, a change in the level of either time or UV-C irradiance did not affect the effectiveness of UV-C light for A. fischeri and P. niveus inactivation. Thus, the modeling of the inactivation as a function of the UV-C fluence allowed the estimation of the primary model parameters with all experimental data and, consequently, no secondary models were needed. The model parameters were validated with experiments of variable UV-C fluences. Accordingly, experimental results allowed to conclude that UV-C treatment at the irradiances tested is a promising application for preventing A. fischeri and P. niveus spoilage of juices.

Mycotoxin-Producing Fungal Species Recovered from Melon Seed Marketed in Nigeria

Agricultural products may be contaminated by mycotoxin-producing pathogenic fungi while on the field or during harvesting and storage. A field survey was conducted in order to isolate and identify the mycotoxin-producing fungal strains in melon seeds collected from major markets in eight States in Nigeria. Samples per site were pooled, processed and screened for the presence of mycotoxin-producing fungi by culture technique and Internal transcribed spacer sequencing (ITS). Mycotoxin production was determined using thin-layer chromatography (TLC) with a scanning densitometer. Eighteen producing fungi species: Macrophomina phaseolina, Aspergillus foetidus, Aspergillus flavipes, Rhizopus oryzae, Aspergillus flavus, Aspergillus niger, Penicillium aurantiocandidum, Aspergillus awamori, Neurospora crassa, Aspergillus fischeri, Aspergillus flavus, Aspergillus tamarii, Aspergillus oryzae, Lichtheimia hyalospora, Aspergillus terreus, Rhizopus oryzae, Aspergillus welwitschiae, Aspergillus corrugatus were identified. These sequences with accession numbers between MN423295-MN423331 have been deposited at the National Center for Biotechnology Information (NCBI) database. The genera Macrophomina and were the most dominant. Some of the identified fungi are noted for the production of mycotoxins and mycotoxins exert toxic effects on animals and humans. The fungi associated to melon seeds diseases were identified and can be taken as targets in the varietal improvement of melon seeds for resistance to fungal diseases in Nigeria.

Comparing thermal inactivation to a combined process of moderate heat and high pressure: Effect on ascospores in strawberry puree

High pressure processing is a mild preservation process that inactivates pathogenic and spoilage micro-organisms in food products, but preserves the fresh characteristics of a product. Compared to untreated product, an enhanced shelf life is obtained during refrigerated storage. Knowledge on the use of high pressure pasteurisation aimed for ambient storage is limited.The aim of this research was to investigate if a combination of high pressure and moderate heat could be used to produce a shelf-stable high-acid fruit product. Ascospores of the heat resistant fungi Talaromyces macrosporus and Aspergillus fischeri were added to fresh strawberry puree that served as a model system. The effect of the processing steps and storage at ambient temperature for 2 weeks was studied on viability of the ascospores.A preheating step at 69 °C/2 min resulted in full or partial activation of A. fischeri and T. macrosporus spores, respectively. The pressure build-up by the process without any holding time resulted in additional activation of spores. A combination of moderate heat (maximum 85–90 °C) and high pressure (500–700 MPa) for holding times up to 13 min inactivated these highly resistant spores much faster than a heat treatment alone. At Tmax = 85 °C and 600 MPa the spores of T. macrosporus and A. fischeri were inactivated by 5.0 and 5.5 log10 after 13 and 7 min, respectively. At Tmax = 85 °C the heat treatment alone did not reduce the viability of these spores up to 60 min of treatment. At Tmax = 90 °C the holding time of the combined pressure-heat treatment could be reduced to obtain the same degree of inactivation of the heat resistant fungi.In addition, treated and untreated ascospores in strawberry puree were stored for 14 days at room temperature to evaluate delayed outgrowth of spores. Untreated ascospores of A. fischeri were activated by storage in the puree. However, at conditions combining high pressure ≥ 600 MPa with Tmax ≥ 85 °C for 13 min, heat resistant fungi were successfully inactivated.This research showed that a combination of moderate heat and pressure can drastically improve the effectiveness to inactivate heat-resistant ascospores in a high-acid fruit product compared to a heat treatment, potentially resulting in a better product quality.

Resistant moulds as pasteurization target for cold distributed high pressure and heat assisted high pressure processed fruit products

High pressure processing (HPP), also known as high hydrostatic pressure (HHP) is a modern method of food pasteurization used commercially in many countries. It relies on the application of very high pressures (up to 600 MPa) to the food/beverage to inactivate microorganisms. Since no heat or mild heat is applied, most of the original food sensory, nutrient and functional properties are retained after processing, and fresh-like fruit products with longer shelf-life are produced. In this study, a review of the resistance to HPP and HPTP (high pressure thermal process) of key bacteria, moulds and yeasts which often contaminate fruit products was undertaken. Spores of moulds Byssochlamys nivea - anamorph name Paecilomyces niveus or Neosartorya fischeri - anamorph name Aspergillus fischeri, are very resistant. A HPTP process of 600 MPa-75°C-15 min only caused a reduction of 1.4 log. Moulds are able to grow at temperatures between 10 and 43 °C, water activity between 0.892 and 0.992, over a wide range of pH (3–8), under reduced oxygen conditions inside food packs and in carbonated beverages, sometimes producing mycotoxins. Furthermore, HPP treated fruit products are cold stored, and therefore moulds can be an issue as they grow at temperatures as low as 10 °C. Therefore, in view of the acidity of fruit products, the high resistance to HPTP in particular older spores, the use of B. nivea or N. fischeri spores as reference microorganisms in the design of new HPP and HPTP processes with fruit products was proposed.

Wheldone: Characterization of a Unique Scaffold from the Coculture of Aspergillus fischeri and Xylaria flabelliformis.

Wheldone (1) was isolated and elucidated from a coculture of Aspergillus fischeri (NRRL 181) and Xylaria flabelliformis (G536), where secondary metabolite biosynthesis was stimulated by antagonism between these fungi. First observed via in situ analysis between these competing fungal cultures, the conditions were scaled to reproducibly generate 1, whose novel structure was elucidated by one- and two-dimensional NMR and mass spectrometry. Compound 1 displayed cytotoxic activity against breast, ovarian, and melanoma cancer cell lines.

Gliotoxin, a Known Virulence Factor in the Major Human Pathogen Aspergillus fumigatus, Is Also Biosynthesized by Its Nonpathogenic Relative Aspergillus fischeri.

Aspergillus fumigatus is a major opportunistic human pathogen. Multiple traits contribute to A. fumigatus pathogenicity, including its ability to produce specific secondary metabolites, such as gliotoxin. Gliotoxin is known to inhibit the host immune response, and genetic mutants that inactivate gliotoxin biosynthesis (or secondary metabolism in general) attenuate A. fumigatus virulence. The genome of Aspergillus fischeri, a very close nonpathogenic relative of A. fumigatus, contains a biosynthetic gene cluster that is homologous to the A. fumigatus gliotoxin cluster. However, A. fischeri is not known to produce gliotoxin. To gain further insight into the similarities and differences between the major pathogen A. fumigatus and the nonpathogen A. fischeri, we examined whether A. fischeri strain NRRL 181 biosynthesizes gliotoxin and whether the production of secondary metabolites influences the virulence profile of A. fischeri We found that A. fischeri biosynthesizes gliotoxin under the same conditions as A. fumigatus However, whereas loss of laeA, a master regulator of secondary metabolite production (including gliotoxin biosynthesis), has previously been shown to reduce A. fumigatus virulence, we found that laeA loss (and loss of secondary metabolite production) in A. fischeri does not influence its virulence. These results suggest that LaeA-regulated secondary metabolites are virulence factors in the genomic and phenotypic background of the major pathogen A. fumigatus but are much less important in the background of the nonpathogen A. fischeri Understanding the observed spectrum of pathogenicity across closely related pathogenic and nonpathogenic Aspergillus species will require detailed characterization of their biological, chemical, and genomic similarities and differences.IMPORTANCEAspergillus fumigatus is a major opportunistic fungal pathogen of humans, but most of its close relatives are nonpathogenic. Why is that so? This important, yet largely unanswered, question can be addressed by examining how A. fumigatus and its close nonpathogenic relatives are similar or different with respect to virulence-associated traits. We investigated whether Aspergillus fischeri, a nonpathogenic close relative of A. fumigatus, can produce gliotoxin, a mycotoxin known to contribute to A. fumigatus virulence. We discovered that the nonpathogenic A. fischeri produces gliotoxin under the same conditions as those of the major pathogen A. fumigatus However, we also discovered that, in contrast to what has previously been observed in A. fumigatus, the loss of secondary metabolite production in A. fischeri does not alter its virulence. Our results are consistent with the "cards of virulence" model of opportunistic fungal disease, in which the ability to cause disease stems from the combination ("hand") of virulence factors ("cards") but not from individual factors per se.