Mycotoxins - Their Biosynthesis in Fungi: Aflatoxins and other Bisfuranoids

1979 ◽  
Vol 42 (10) ◽  
pp. 805-809 ◽  
Author(s):  
J. W. BENNETT ◽  
L. S. LEE
Keyword(s):  
Experimental Data ◽  
Secondary Metabolites ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Fungal Metabolites ◽  
Aflatoxin Biosynthesis ◽  
Mechanism Of Formation ◽  
13C Labeling

Aflatoxins are a family of highly toxic and carcinogenic secondary metabolites produced by certain strains of Aspergillus flavus and Aspergillus parasiticus. Biosynthetically, the aflatoxins are produced by a polyketide pathway. Most of the experimental data on aflatoxin biosynthesis are derived from 14C- and 13C-labeling experiments and use of blocked mutants. These data indicate that the general steps in aflatoxin biosynthesis are acetate → anthraquinones → sterigmatocystin → aflatoxin B1. Many details of the pathway remain unresolved; it is hoped that further research, particularly with cell-free systems, will improve our understanding of the mechanism of formation of these important fungal metabolites.

scholarly journals Natural Occurence of Aflatoxins in Wheat from Central Transylvania

2011 ◽  
Vol 68 (2) ◽  
Author(s):  
Simona MAN ◽  
Maria TOFANA ◽  
Sevastiţa MUSTE ◽  
Adriana PAUCEAN ◽  
Anamaria BIROU (POP)
Keyword(s):  
Secondary Metabolites ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Economic Losses ◽  
Important Food ◽  
And Storage ◽  
Harmful Effects

Aflatoxins (AFs), the secondary metabolites produced by species of Aspergillus, specifically Aspergillus flavus and Aspergillus parasiticus, have harmful effects on humans, animals, and crops that result in illnesses and economic losses. Wheat that is susceptible to these fungi infections through its growth, harvest, transport, and storage, is the most important food in Romania. Therefore, this study sought to present mycotoxins in wheat samples grown in different regions of Transyvania, the results being obtained in the climate of the year 2009-2010. Wheat samples were collected from Turda and Targu Mures. It was analyzed the presence of aflatoxins B1, B2, G1, G2, using HPTLC in twenty samples of wheat. Percentage of samples found positive for aflatoxin B1, B2, G1, G2 was 10%, 5%, 0%, 0%. Although the percentage of aflatoxin found in wheat is low, these percentages should be considered, in terms of exposure every day to mycotoxins through consumption of cereals and cereal-based products.

scholarly journals Production of aflatoxins and aflatoxicols by Aspergillus flavus and Aspergillus parasiticus and metabolism of aflatoxin B1 by aflatoxin-non-producing Aspergillus flavus.

Eisei kagaku ◽  
1991 ◽  
Vol 37 (2) ◽  
pp. 107-116 ◽  
Author(s):  
MITSUO NAKAZATO ◽  
SATOSHI MOROZUMI ◽  
KAZUO SAITO ◽  
KENJI FUJINUMA ◽  
TAICHIRO NISHIMA ◽  
...  
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus

scholarly journals Vibrio gazogenes inhibits aflatoxin production through downregulation of aflatoxin biosynthetic genes in Aspergillus flavus

2022 ◽  
Author(s):  
Shyam L. Kandel ◽  
Rubaiya Jesmin ◽  
Brian M. Mack ◽  
Rajtilak Majumdar ◽  
Matthew K. Gilbert ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Secondary Metabolite ◽  
Aspergillus Flavus ◽  
Fungal Biomass ◽  
Expression Profiles ◽  
Health Hazard ◽  
Gene Clusters ◽  
Aflatoxin Contamination ◽  
Aflatoxin Biosynthesis ◽  
Control Samples

Aspergillus flavus is an opportunistic pathogen of oilseed crops such as maize, peanut, cottonseed, and tree nuts and produces carcinogenic secondary metabolites known as aflatoxins during seed colonization. Aflatoxin contamination not only reduces the value of the produce but also is a health hazard to humans and animals. Previously, we observed inhibition of A. flavus aflatoxin biosynthesis upon exposure to the marine bacterium, Vibrio gazogenes (Vg). In this study, we used RNA sequencing to examine the transcriptional profiles of A. flavus treated with both live and heat-inactivated dead Vg and control samples. Fungal biomass, total accumulated aflatoxins, and expression profiles of genes constituting secondary metabolite biosynthetic gene clusters were determined at 24, 30, and 40 h after treatment. Statistically significant reductions in total aflatoxins were detected in Vg-treated samples as compared to control samples at 40 h. But no statistical difference in fungal biomass was observed upon these treatments. The Vg treatments were most effective on aflatoxin biosynthesis as was reflected in significant downregulation of majority of the genes in the aflatoxin gene cluster including the aflatoxin pathway regulator gene, aflR. Along with aflatoxin genes, we also observed significant downregulation in some other secondary metabolite gene clusters including cyclopiazonic acid and aflavarin, suggesting that the treatment may inhibit other secondary metabolites as well. Finally, a weighted gene correlation network analysis identified an upregulation of ten genes that were most strongly associated with Vg-dependent aflatoxin inhibition and provide a novel start-point in understanding the mechanisms that result in this phenomenon.

Effects of Potassium Sorbate on Growth and Aflatoxin Production by Aspergillus parasiticus and Aspergillus flavus1

1983 ◽  
Vol 46 (11) ◽  
pp. 940-942 ◽  
Author(s):  
LLOYD B. BULLERMAN
Keyword(s):  
Aspergillus Flavus ◽  
Yeast Extract ◽  
Aflatoxin B1 ◽  
Spore Germination ◽  
Mycelial Growth ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Production ◽  
Potassium Sorbate ◽  
Mycelial Mass ◽  
Yeast Extract Sucrose

Growth and aflatoxin production by selected strains of Aspergillus parasiticus and Aspergillus flavus in the presence of potassium sorbate at 12°C were studied. Potassium sorbate at 0.05, 0.10 and 0.15% delayed or prevented spore germination and initiation of growth, and slowed growth of these organisms in yeast-extract sucrose broth at 12°C. Increasing concentrations of sorbate caused more variation in the amount of total mycelial growth and generally resulted in a decrease in total mycelial mass. Potassium sorbate also greatly reduced or prevented production of aflatoxin B1 by A. parasiticus and A. flavus for up to 70 d at 12°C. At 0.10 and 0.15% of sorbate, aflatoxin production was essentially eliminated. A 0.05% sorbate, aflatoxin production was greatly decreased in A. flavus over the control, but only slightly decreased in A. parasiticus.

scholarly journals Impact of Silver Nanoparticles on Gene Expression in Aspergillus Flavus Producer Aflatoxin B1

2018 ◽  
Vol 6 (4) ◽  
pp. 600-605 ◽  
Author(s):  
Mohamed Mahmoud Deabes ◽  
Wagdy Khalil Bassaly Khalil ◽  
Ashraf Gamil Attallah ◽  
Tarek Ahmed El-Desouky ◽  
Khayria Mahmoud Naguib
Keyword(s):  
Silver Nanoparticles ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Inhibitory Effect ◽  
Aflatoxin Biosynthesis ◽  
Qrt Pcr ◽  
Methyltransferase Gene ◽  
Polymerase Chain ◽  
Yeast Extract Sucrose ◽  
Quantitative Pcr Assay

AIM: In this study, we evaluated the effect of silver nanoparticles (AgNPs) on the production of aflatoxin B1 (AFB1) through assessment the transcription activity of aflatoxin biosynthesis pathway genes in Aspergillus flavus ATCC28542.MATERIAL AND METHODS: The mRNAs were quantitative by Real Time-polymerase chain reaction (qRT-PCR) of A. flavus grown in yeast extract sucrose (YES) medium containing AgNPs. Specific primers that are involved in the AFB1 biosynthesis which highly specific to A. flavus, O-methyltransferase gene (omt-A), were designed and used to detect the fungus activity by quantitative PCR assay. The AFB1 production (from A. flavus growth) which effected by AgNPs were measured in YES medium by high-pressure liquid chromatography (HPLC).RESULTS: The AFB1 produced by A. flavus have the highest reduction with 1.5 mg -100 ml of AgNPs were added in media those records 88.2%, 67.7% and 83.5% reduction by using AgNP HA1N, AgNP HA2N and AgNP EH, respectively. While on mycelial growth give significantly inhibitory effect. These results have been confirmed by qRT-PCR which showed that culture of A. flavus with the presence of AgNPs reduced the expression levels of omt-A gene.CONCLUSION: Based on the results of the present study, AgNPs inhibit growth and AFB1 produced by Aspergillus flavus ATCC28542. This was confirmed through RT-PCR approach showing the effect of AgNPs on omt-A gene involved in aflatoxin biosynthesis.

scholarly journals Osmotic-Adaptation Response of sakA/hogA Gene to Aflatoxin Biosynthesis, Morphology Development and Pathogenicity in Aspergillus flavus

Toxins ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 41 ◽  
Author(s):  
Elisabeth Tumukunde ◽  
Ding Li ◽  
Ling Qin ◽  
Yu Li ◽  
Jiaojiao Shen ◽  
...  
Keyword(s):  
Osmotic Stress ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Wall Stress ◽  
Mitogen Activated Protein Kinase ◽  
Human Beings ◽  
Aflatoxin Biosynthesis ◽  
Wild Type ◽  
Adaptation Response ◽  
Seed Crops

Aspergillus flavus is one of the fungi from the big family of Aspergillus genus and it is capable of colonizing a large number of seed/crops and living organisms such as animals and human beings. SakA (also called hogA/hog1) is an integral part of the mitogen activated protein kinase signal of the high osmolarity glycerol pathway. In this study, the AfsakA gene was deleted (∆AfsakA) then complemented (∆AfsakA::AfsakA) using homologous recombination and the osmotic stress was induced by 1.2 mol/L D-sorbital and 1.2 mol/L sodium chloride. The result showed that ∆AfsakA mutant caused a significant influence on conidial formation compared to wild-type and ∆AfsakA::AfsakA strains. It was also found that AfsakA responds to both the osmotic stress and the cell wall stress. In the absence of osmotic stress, ∆AfsakA mutant produced more sclerotia in contrast to other strains, whereas all strains failed to generate sclerotia under osmotic stress. Furthermore, the deletion of AfsakA resulted in the increase of Aflatoxin B1 production compared to other strains. The virulence assay on both maize kernel and peanut seeds showed that ∆AfsakA strain drastically produced more conidia and Aflatoxin B1 than wild-type and complementary strains. AfSakA-mCherry was located to the cytoplasm in the absence of osmotic stress, while it translocated to the nucleus upon exposure to the osmotic stimuli. This study provides new insights on the development and evaluation of aflatoxin biosynthesis and also provides better understanding on how to prevent Aspergillus infections which would be considered the first step towards the prevention of the seeds damages caused by A. flavus.

PRODUCTION OF AFLATOXIN IN CONCENTRATED AND DILUTED GRAPEFRUIT JUICE1

1974 ◽  
Vol 37 (7) ◽  
pp. 395-398 ◽  
Author(s):  
G. G. Alderman ◽  
E. H. Marth
Keyword(s):  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Grapefruit Juice ◽  
Aspergillus Parasiticus ◽  
Soluble Solids ◽  
Soluble Solids Content ◽  
Initial Value ◽  
Visible Growth ◽  
Solids Content

Commercial concentrated and diluted (1:1, 1:2, 1:3; juice: water) steamed grapefruit juice was inoculated with known aflatoxigenic aspergilli and sampled after 10 and 14 days of incubation at 28 C. When Aspergillus flavus grew in juice, most aflatoxin B1 (0.211 μg/ml appeared in concentrated juice and least (0.013 μg/ml) in single strength juice. Juices diluted 1:1 and 1:2 yielded 0.078 and 0.020 μg B1/ml, respectively. Results were more striking when Aspergillus parasiticus grew in samples of juice. After 10 days, amounts of aflatoxin B1 in concentrated juice and in concentrated juice diluted 1:1, 1:2, and 1:3 were 7.5, 1.59, 0.69, and 0.56 μg/ml, respectively. Aflatoxins B2, G1, and G2 were also produced and greatest amounts also developed in concentrated juice. Amounts of these toxins decreased markedly when the percentage of soluble solids in the juices decreased. Fourteen instead of 10 days of incubation resulted in increases in the amount of each toxin in concentrated juice and in concentrated juice diluted 1:1. Although the greatest amount of aflatoxin occurred in concentrated juice, appearance of visible growth and onset of sporulation by the molds was slower in this than in diluted juices. The pH of the concentrated juice did not change appreciably after 10 and 14 days of incubation, but the pH of diluted juices rose progressively from the initial value as the percent soluble solids content in the juice decreased.

Resistance to Aflatoxin Contamination in Corn as Influenced by Relative Humidity and Kernel Germination

1996 ◽  
Vol 59 (3) ◽  
pp. 276-281 ◽  
Author(s):  
B. Z. GUO ◽  
J. S. RUSSIN ◽  
R. L. BROWN ◽  
T. E. CLEVELAND ◽  
N. W. WIDSTROM
Keyword(s):  
Relative Humidity ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Resistance Mechanisms ◽  
Aflatoxin Contamination ◽  
Aflatoxin Biosynthesis ◽  
Aflatoxin Accumulation ◽  
Moisture Conditions ◽  
Very High ◽  
Fungus Growth

Kernels of corn population GT-MAS:gk, resistant to aflatoxin B1 production by Aspergillus flavus, and susceptible Pioneer hybrid 3154 were tested for aflatoxin when incubated under different relative humidities (RH). High aflatoxin levels were not detected in either genotype at RH < 91%. Resistance in GT-MAS:gk was consistent across all RH levels (91 to 100%) at which significant aflatoxin accumulation was detected. Aflatoxin levels in GT-MAS:gk averaged about 98% less than those in susceptible Pioneer 3154, which suggests that storage of this or other genotypes with similar resistance mechanisms may be possible under moisture conditions less exacting than are required with susceptible hybrids. Results for fungus growth and sporulation ratings on kernel surfaces were similar to those for aflatoxin levels. When kernels of both genotypes were preincubated 3 days at 100% RH prior to inoculation with A. flavus, germination percentages increased to very high levels compared to those of kernels that were not preincubated. In preincubated kernels aflatoxin levels remained consistently low in GT-MAS:gk but decreased markedly (61%) in Pioneer 3154. When eight susceptible hybrids were evaluated for aflatoxin accumulation in preincubated kernels, seven of these supported significantly lower toxin levels than kernels not subjected to preincubation. Average reduction across hybrids was 83%, and reductions within hybrids ranged from 68 to 96%. Preincubated kernels of one susceptible hybrid (Deltapine G-4666) supported aflatoxin levels comparable to those in resistant GT-MAS:gk. Data suggest that an inhibitor of aflatoxin biosynthesis may be induced during kernel germination. Possible mechanisms for embryo effects on resistance to aflatoxin accumulation are discussed.

scholarly journals The bZIP Transcription Factor AflRsmA Regulates Aflatoxin B1 Biosynthesis, Oxidative Stress Response and Sclerotium Formation in Aspergillus flavus

Toxins ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 271
Author(s):  
Xiuna Wang ◽  
Wenjie Zha ◽  
Linlin Liang ◽  
Opemipo Esther Fasoyin ◽  
Lihan Wu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Transcription Factor ◽  
Stress Response ◽  
Secondary Metabolites ◽  
Secondary Metabolism ◽  
Aspergillus Flavus ◽  
Aflatoxin B1 ◽  
Opportunistic Pathogen ◽  
Oxidative Stress Response ◽  
Bzip Transcription Factor

Fungal secondary metabolites play important roles not only in fungal ecology but also in humans living as beneficial medicine or harmful toxins. In filamentous fungi, bZIP-type transcription factors (TFs) are associated with the proteins involved in oxidative stress response and secondary metabolism. In this study, a connection between a bZIP TF and oxidative stress induction of secondary metabolism is uncovered in an opportunistic pathogen Aspergillus flavus, which produces carcinogenic and mutagenic aflatoxins. The bZIP transcription factor AflRsmA was identified by a homology research of A. flavus genome with the bZIP protein RsmA, involved in secondary metabolites production in Aspergillus nidulans. The AflrsmA deletion strain (ΔAflrsmA) displayed less sensitivity to the oxidative reagents tert-Butyl hydroperoxide (tBOOH) in comparison with wild type (WT) and AflrsmA overexpression strain (AflrsmAOE), while AflrsmAOE strain increased sensitivity to the oxidative reagents menadione sodium bisulfite (MSB) compared to WT and ΔAflrsmA strains. Without oxidative treatment, aflatoxin B1 (AFB1) production of ΔAflrsmA strains was consistent with that of WT, but AflrsmAOE strain produced more AFB1 than WT; tBOOH and MSB treatment decreased AFB1 production of ΔAflrsmA compared to WT. Besides, relative to WT, ΔAflrsmA strain decreased sclerotia, while AflrsmAOE strain increased sclerotia. The decrease of AFB1 by ΔAflrsmA but increase of AFB1 by AflrsmAOE was on corn. Our results suggest that AFB1 biosynthesis is regulated by AflRsmA by oxidative stress pathways and provide insights into a possible function of AflRsmA in mediating AFB1 biosynthesis response host defense in pathogen A. flavus.

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