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Current Microbiology Aug 2020This study investigated the fermentation kinetics and thermodynamics of ascorbic acid production from Brewery Spent Grain (BSG) using Aspergillus flavus and Aspergillus...
This study investigated the fermentation kinetics and thermodynamics of ascorbic acid production from Brewery Spent Grain (BSG) using Aspergillus flavus and Aspergillus tamarii. Ascorbic acid fermentation of A. flavus and A. tamarii was performed at a temperature of 30 °C, agitation speed of 100 rpm and pH 5.0 at 96 h of fermentation. The thermodynamics, kinetics of the growth parameters and ascorbic acid production were studied using Monod, Contois and Teisser models. Teisser model gave the best fit as it obtained the highest maximum specific growth rate (µ) and correlation coefficient of 0.184 h and 0.997, respectively, at 40 °C, pH 5.0 and 0.6 g of BSG. The result showed that Teisser model gave a better description of each growth parameter. Hence, the production of ascorbic acid by A. flavus and A. tamarii is growth-associated.
Topics: Ascorbic Acid; Aspergillus; Aspergillus flavus; Fermentation; Kinetics; Temperature; Thermodynamics
PubMed: 32236648
DOI: 10.1007/s00284-020-01960-1 -
Microbiology Spectrum Aug 2023Aspergillus flavus is a mycotoxigenic fungus that contaminates many important agricultural crops with aflatoxin B1, the most toxic and carcinogenic natural compound....
Aspergillus flavus is a mycotoxigenic fungus that contaminates many important agricultural crops with aflatoxin B1, the most toxic and carcinogenic natural compound. This fungus is also the second leading cause of human invasive aspergillosis, after Aspergillus fumigatus, a disease that is particularly prevalent in immunocompromised individuals. Azole drugs are considered the most effective compounds in controlling Aspergillus infections both in clinical and agricultural settings. Emergence of azole resistance in Aspergillus spp. is typically associated with point mutations in orthologs that encode lanosterol 14α-demethylase, a component of the ergosterol biosynthesis pathway that is also the target of azoles. We hypothesized that alternative molecular mechanisms are also responsible for acquisition of azole resistance in filamentous fungi. We found that an aflatoxin-producing A. flavus strain adapted to voriconazole exposure at levels above the MIC through whole or segmental aneuploidy of specific chromosomes. We confirm a complete duplication of chromosome 8 in two sequentially isolated clones and a segmental duplication of chromosome 3 in another clone, emphasizing the potential diversity of aneuploidy-mediated resistance mechanisms. The plasticity of aneuploidy-mediated resistance was evidenced by the ability of voriconazole-resistant clones to revert to their original level of azole susceptibility following repeated transfers on drug-free media. This study provides new insights into mechanisms of azole resistance in a filamentous fungus. Fungal pathogens cause human disease and threaten global food security by contaminating crops with toxins (mycotoxins). Aspergillus flavus is an opportunistic mycotoxigenic fungus that causes invasive and noninvasive aspergillosis, diseases with high rates of mortality in immunocompromised individuals. Additionally, this fungus contaminates most major crops with the notorious carcinogen, aflatoxin. Voriconazole is the drug of choice to treat infections caused by Aspergillus spp. Although azole resistance mechanisms have been well characterized in clinical isolates of Aspergillus fumigatus, the molecular basis of azole resistance in A. flavus remains unclear. Whole-genome sequencing of eight voriconazole-resistant isolates revealed that, among other factors, A. flavus adapts to high concentrations of voriconazole by duplication of specific chromosomes (i.e., aneuploidy). Our discovery of aneuploidy-mediated resistance in a filamentous fungus represents a paradigm shift, as this type of resistance was previously thought to occur only in yeasts. This observation provides the first experimental evidence of aneuploidy-mediated azole resistance in the filamentous fungus A. flavus.
Topics: Aspergillus flavus; Voriconazole; Aneuploidy; Drug Resistance, Fungal; Gene Dosage; Chromosomes, Fungal; Antifungal Agents
PubMed: 37358460
DOI: 10.1128/spectrum.04339-22 -
Applied and Environmental Microbiology Mar 2019is an opportunistic fungal plant and human pathogen and a producer of mycotoxins, including aflatoxin B (AFB). As part of our ongoing studies to elucidate the...
is an opportunistic fungal plant and human pathogen and a producer of mycotoxins, including aflatoxin B (AFB). As part of our ongoing studies to elucidate the biological functions of the gene, we examined its role in the pathogenicity of both plant and animal model systems. encodes a putative RNA polymerase II (Pol II) transcription elongation factor previously characterized in , , and , where it was shown to regulate several important cellular processes, including morphogenesis and secondary metabolism. In addition, an initial study in indicated that also influences development and production of AFB; however, its effect on virulence is unknown. The current study reveals that the gene is indispensable for normal pathogenicity in plants when using peanut seed as an infection model, as well as in animals, as shown in the infection model. Interestingly, positively regulates several processes known to be necessary for successful fungal invasion and colonization of host tissue, such as adhesion to surfaces, protease and lipase activity, cell wall composition and integrity, and tolerance to oxidative stress. In addition, metabolomic analysis revealed that affects the production of several secondary metabolites, including AFB, aflatrem, leporins, aspirochlorine, ditryptophenaline, and aflavinines, supporting a role of as a global regulator of secondary metabolism. Heterologous complementation of an deletion strain with homologs from or fully rescued the wild-type phenotype, indicating that these homologs are functionally conserved among these three species. In this study, the epigenetic global regulator , which encodes a putative RNA-Pol II transcription elongation factor-like protein, was characterized in the mycotoxigenic and opportunistic pathogen Specifically, its involvement in pathogenesis in plant and animal models was studied. Here, we show that positively regulates virulence in both models. Furthermore, -dependent effects on factors necessary for successful invasion and colonization of host tissue by were also assessed. Our study indicates that plays a role in adherence to surfaces, hydrolytic activity, normal cell wall formation, and response to oxidative stress. This study also revealed a profound effect of on the metabolome of , including the production of potent mycotoxins.
Topics: Aflatoxin B1; Animals; Arachis; Aspergillus flavus; Fungal Proteins; Gene Expression Regulation, Fungal; Moths; Plant Diseases; Secondary Metabolism; Transcriptional Elongation Factors; Virulence
PubMed: 30635379
DOI: 10.1128/AEM.02446-18 -
Fungal Biology Oct 2016Aspergillus flavus is able to synthesize a variety of polyketide-derived secondary metabolites including the hepatocarcinogen, aflatoxin B1. The fungus reproduces and...
Aspergillus flavus is able to synthesize a variety of polyketide-derived secondary metabolites including the hepatocarcinogen, aflatoxin B1. The fungus reproduces and disseminates predominantly by production of conidia. It also produces hardened mycelial aggregates called sclerotia that are used to cope with unfavourable growth environments. In the present study, we examined the role of A. flavus fluP, the backbone polyketide synthase gene of secondary metabolite gene cluster 41, on fungal development. The A. flavus CA14 fluP deletion mutant (AfΔfluP) grew and accumulated aflatoxin normally but produced a lower amount of sclerotia than the parental strain. This was also true for the Aspergillus parasiticus BN9 fluP deletion mutant (ApΔfluP). The A. flavus fluP gene was positively regulated by developmental regulators of VeA and VelB but not by the global regulator of secondary metabolism, LaeA. Overexpression of fluP in AfΔfluP (OEfluP) elevated its ability to produce sclerotia compared to that of the parental strain. Coculture of OEfluP with CA14, AfΔfluP, ApΔfluP, or an A. flavus pptA deletion mutant incapable of producing functional polyketide synthases also allowed increased sclerotial production of the respective strains at edges where colonies made contact. Acetone extracts of OEfluP but not of AfΔfluP exhibited the same effect in promoting sclerotial production of AfΔfluP. These results suggest that FluP polyketide synthase is involved in the synthesis of a diffusible metabolite that could serve as a signal molecule to regulate sclerotiogenesis.
Topics: Aspergillus flavus; Fungal Proteins; Gene Expression Regulation, Fungal; Mycelium; Polyketide Synthases; Secondary Metabolism
PubMed: 27647242
DOI: 10.1016/j.funbio.2016.07.010 -
Journal of Agricultural and Food... Sep 2016Small ubiquitin-like modifiers (SUMOs) can be reversibly attached to target proteins in a process known as SUMOylation, and this process influences several important...
Small ubiquitin-like modifiers (SUMOs) can be reversibly attached to target proteins in a process known as SUMOylation, and this process influences several important eukaryotic cell events. However, little is known regarding SUMO or SUMOylation in Aspergillus flavus. Here, we identified a novel member of the SUMO family in A. flavus, AfSumO, and validated the existence of SUMOylation in this pathogenic filamentous fungus. We investigated the roles of AfsumO in A. flavus by determining the effects of AfsumO mutations on the growth phenotype, stress response, conidia and sclerotia production, aflatoxin biosynthesis, and pathogenicity to seeds, and we found that SUMOylation plays a role in fungal virulence and toxin attributes. Taken together, these results not only reveal potential mechanisms of fungal virulence and toxin attributes in A. flavus but also provide a novel approach for promising new control strategies of this fungal pathogen.
Topics: Aflatoxins; Arachis; Aspergillus flavus; Fungal Proteins; Plant Diseases; SUMO-1 Protein; Spores, Fungal; Virulence
PubMed: 27532332
DOI: 10.1021/acs.jafc.6b02199 -
Toxins May 2023Aflatoxins are immunosuppressive and carcinogenic secondary metabolites, produced by the filamentous ascomycete , that are hazardous to animal and human health. In this...
Aflatoxins are immunosuppressive and carcinogenic secondary metabolites, produced by the filamentous ascomycete , that are hazardous to animal and human health. In this study, we show that multiplexed host-induced gene silencing (HIGS) of genes essential for fungal sporulation and aflatoxin production (, , , and confers enhanced resistance to infection and aflatoxin contamination in groundnut (<20 ppb). Comparative proteomic analysis of contrasting groundnut genotypes (WT and near-isogenic HIGS lines) supported a better understanding of the molecular processes underlying the induced resistance and identified several groundnut metabolites that might play a significant role in resistance to infection and aflatoxin contamination. Fungal differentiation and pathogenicity proteins, including calmodulin, transcriptional activator-HacA, kynurenine 3-monooxygenase 2, VeA, VelC, and several aflatoxin pathway biosynthetic enzymes, were downregulated in infecting the HIGS lines. Additionally, in the resistant HIGS lines, a number of host resistance proteins associated with fatty acid metabolism were strongly induced, including phosphatidylinositol phosphate kinase, lysophosphatidic acyltransferase-5, palmitoyl-monogalactosyldiacylglycerol Δ-7 desaturase, ceramide kinase-related protein, sphingolipid Δ-8 desaturase, and phospholipase-D. Combined, this knowledge can be used for groundnut pre-breeding and breeding programs to provide a safe and secure food supply.
Topics: Humans; Animals; Aspergillus flavus; Aflatoxins; Proteomics; Arachis; Plant Breeding; Aspergillosis; Gene Silencing
PubMed: 37235354
DOI: 10.3390/toxins15050319 -
Toxicon : Official Journal of the... Apr 2018Aspergillus flavus is a common fungal pathogen of plants, animals and humans. Recently, many genes of A. flavus have been reported involving in regulation of...
Aspergillus flavus is a common fungal pathogen of plants, animals and humans. Recently, many genes of A. flavus have been reported involving in regulation of pathogenesis in crops, but whether these genes are involved in animal virulence is still unknown. Here, we used a previous easy-to-use infection model for A. flavus based on mouse model by intravenous inoculation of A. flavus conidia. The outcome of infections in mice model showed that A. flavus NRRL3357 and laboratory strain CA14 PTS were both in dose dependent manner and highly reproducible. The progress of disease could be monitored by mice survival and histology analysis. Fungal burden analysis indicated it was gradually decreased within 7 days after infection. Moreover, aspergillosis caused by A. flavus significantly up-regulated gene expression levels of immune response mediators, including INF-γ, TNF-α, Dectin-1 and TLR2. Furthermore, the defined deletion A. flavus strains that previously displayed virulence in crop infection were also determined in this mouse model, and the results showed comparable degrees of infection in mice. Our results suggested that intravenous inoculation of conidia could be a suitable model for testing different A. flavus mutants in animal virulence. We hope to use this model to determine distinct A. flavus strains virulence in animals and study novel therapeutic methods to help control fungus diseases in the future.
Topics: Administration, Intravenous; Animals; Aspergillosis; Aspergillus flavus; Disease Models, Animal; Female; Gene Expression; Lung; Mice, Inbred ICR; Virulence
PubMed: 29481813
DOI: 10.1016/j.toxicon.2018.02.043 -
Journal of Applied Microbiology Nov 2019To use genome-wide single nucleotide polymorphisms (total SNPs) to develop a molecular method for distinguishing Aspergillus flavus and Aspergillus oryzae.
AIMS
To use genome-wide single nucleotide polymorphisms (total SNPs) to develop a molecular method for distinguishing Aspergillus flavus and Aspergillus oryzae.
METHODS AND RESULTS
Thirteen A. flavus and eleven A. oryzae genome sequences were obtained from the National Center for Biotechnology Information. These sequences were analysed by Mauve, a multiple-genome alignment program, to extract total SNPs between isolates of A. flavus, A. oryzae, or the two species. Averages of total SNPs of A. flavus isolates belonging to the same sclerotial morphotype (L-type = 178 952 ± 14 033; S-type = 133 188 ± 16 430) and A. oryzae isolates (152 336 ± 49 124) were consistently lower than those between the morphotypes and between the two species. Averages of total SNPs for L-type vs S-type (300 116 ± 1562) and S-type A. flavus vs A. oryzae (301 797 ± 4123) were similar but were 36% greater than that of L-type A. flavus vs A. oryzae (226 240 ± 10 779). Based on the devised criterion, ATCC 12892, Aspergillus oryzae (Ahlburg) Cohn, which had an averaged total SNPs 10-fold greater than that of other A. oryzae isolates, was determined to be close to Aspergillus parasiticus. Atoxigenic A. flavus field isolates, WRRL1519 and NRRL35739, were shown to more closely resemble A. oryzae than toxigenic L-type A. flavus. Biocontrol strains AF36 and K49 were genetically close to toxigenic L-type A. flavus. NRRL21882, the active agent of the commercialized biocontrol product Afla-Guard GR, was genetically distant from all other A. flavus isolates.
CONCLUSIONS
The close genetic relatedness between A. flavus and A. oryzae was confirmed and the evolutionary origins of atoxigenic A. flavus biocontrol strains were revealed.
SIGNIFICANCE AND IMPACT OF THE STUDY
The study provides a greater understanding of genome similarity and dissimilarity between A. flavus and A. oryzae. The method can be an auxiliary technique for identifying A. flavus, A. oryzae.
Topics: Aflatoxins; Aspergillus flavus; Aspergillus oryzae; Base Sequence; Genome, Fungal; Polymorphism, Single Nucleotide
PubMed: 31429498
DOI: 10.1111/jam.14419 -
International Journal of Food... Sep 2021Peanut is an important resource of edible oil and digestible protein in daily life, which is rich in the nutriments and antioxidants such as vitamins, minerals and...
Peanut is an important resource of edible oil and digestible protein in daily life, which is rich in the nutriments and antioxidants such as vitamins, minerals and polyphenols. However, peanut is susceptible to the contamination of Aspergillus flavus (A. flavus), which can produce highly carcinogenic toxins that brings serious threats to human health and food safety. Exploring green and effective methods to control A. flavus is meaningful. Herein, a green and economical way to control A. flavus on peanuts was demonstrated. It was found that the growth of A. flavus hyphae and germination of its spores could be inhibited in the presence of α-FeO nanorods under sunlight irradiation according to the agar diffusion method, flat colony counting method and fluorescence-based live/dead test. The diameter of inhibition zone was 22.3 ± 0.2 mm and the inhibition rate of spores germination was about 60 ± 5%, when the concentration of α-FeO was 10 mg/mL for 7 h sunlight irradiation. Most important, α-FeO showed the photocatalytic inhibition of A. flavus on peanuts under sunlight irradiation with the inhibition rate of about 90 ± 5%, and the production of aflatoxin B and aflatoxin B were reduced by 90 ± 2% and 70 ± 3%, respectively. By comparing the fat contents, protein contents, acid value, peroxide value and antioxidative compositions of peanuts, it was found that there was no obvious effect on the quality of peanuts after inhibition treatment. The findings provide a green, safe and economical strategy to control A. flavus on peanuts, which may be as a promising way to be used in food and agro-food preservation.
Topics: Aflatoxins; Antifungal Agents; Arachis; Aspergillus flavus; Nanotubes; Sunlight
PubMed: 34147839
DOI: 10.1016/j.ijfoodmicro.2021.109296 -
Mycopathologia Aug 2011Aspergillus flavus is the second most important Aspergillus species causing human infections. The importance of this fungus increases in regions with a dry and hot... (Review)
Review
Aspergillus flavus is the second most important Aspergillus species causing human infections. The importance of this fungus increases in regions with a dry and hot climate. Small phylogenetic studies in Aspergillus flavus indicate that the morphological species contains several genetically isolated species. Different genotyping methods have been developed and employed in order to better understand the genetic and epidemiological relationships between environmental and clinical isolates. Understanding pathogen distribution and relatedness is essential for determining the epidemiology of nosocomial infections and aiding in the design of rational pathogen control methods. Typing techniques can also give us a deeper understanding of the colonization pattern in patients. Most of these studies focused on Aspergillus fumigatus because it is medically the most isolated species. To date, there has not been any publication exclusively reviewing the molecular typing techniques for Aspergillus flavus in the literature. This article reviews all these different available methods for this organism.
Topics: Aspergillus flavus; Aspergillus fumigatus; Humans; Microsatellite Repeats; Molecular Epidemiology; Molecular Typing; Mycological Typing Techniques; Polymorphism, Restriction Fragment Length
PubMed: 21369748
DOI: 10.1007/s11046-011-9406-x