The Role of Aflatoxins in Aspergillus flavus Resistance to Stress

Mapping Intimacies ◽

10.5772/intechopen.99003 ◽

2021 ◽

Author(s):

Massimo Reverberi ◽

Marzia Beccaccioli ◽

Marco Zaccaria

Keyword(s):

Reactive Oxygen Species ◽

Secondary Metabolites ◽

Natural Population ◽

Aspergillus Flavus ◽

Opportunistic Pathogens ◽

Aspergillus Section Flavi ◽

Resistance To Stress ◽

Niche Competition ◽

Aspergillus Section

Aspergillus section Flavi produce the aflatoxins, secondary metabolites toxic to humans and animals. Why do these fungi produce aflatoxins? They do not have a clear role in pathogenicity or in niche competition. Aspergillus employs a considerable amount of energy to synthesize them: more than 20 enzymatic catalyzes are needed. Within the A. flavus species, all opportunistic pathogens of maize, more than half of the natural population are atoxigenic, indicating that aflatoxins are not so obviously linked to an enhancement of population fitness. The perspective changes in A. parasiticus, pathogen to peanuts, where more than 90% of the natural population produce the four aflatoxins. In this chapter, we aim to discuss our recent hypothesis that aflatoxins act as antioxidants providing more time to Aspergillus to “escape” an exploited substrate, that in the meanwhile is “fully charged” with reactive oxygen species and oxylipins.

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Role of Maize Weevil, Sitophilus zeamais Motsch. on Spread of Aspergillus section flavi in Different Nepalese Maize Varieties

Advances in Agriculture ◽

10.1155/2019/7584056 ◽

2019 ◽

Vol 2019 ◽

pp. 1-5

Author(s):

K. Bhusal ◽

D. Khanal

Keyword(s):

Storage Conditions ◽

Sitophilus Zeamais ◽

Maize Weevil ◽

Aspergillus Section Flavi ◽

Maize Varieties ◽

Maize Variety ◽

Sitophilus Zeamais Motsch ◽

Aspergillus Section ◽

Plot Design

Experiments were conducted to find out the role of maize weevil, Sitophilus zeamais Motsch. on spread of green fungus, Aspergillus section flavi, in different varieties of stored maize in laboratory in 2016. Lab experiment was conducted to find the role of weevil on spread of A. flavus on five main varieties of maize grown at Nepal in split plot design, namely, Arun-2, Arun-4, Manakamana-1, Manakamana-3, and Rampur composite with three replications at NAST, Khumaltar, from August to September 2016. One hundred grams of each maize variety was exposed to weevil along with fungus and with fungus only to see the spread of the fungus under presence and absence of weevil. Among the tested five maize varieties, the lowest infestation was observed on Rampur Composite (14.99%) while it was the highest on Manakamana-3 (87.70%). The highest mean infestation (75.58%) was found under weevil released condition while it was lower (62.16%) under nonreleased condition. In presence of weevil, the infestation of the fungus increased and in their absence the infestation was low which signifies the role of weevil in fungal spread. All indices indicate that Rampur composite is the best variety among the five tested varieties in terms of storage under the presence of fungus and weevils. This study also indicates ample scope for further study on different varieties of maize under several storage conditions.

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Redox-active secondary metabolites act as interspecies modulators of antibiotic resilience

10.1101/2021.12.01.470848 ◽

2021 ◽

Author(s):

Lucas A. Meirelles ◽

Dianne K. Newman

Keyword(s):

Secondary Metabolites ◽

Burkholderia Cepacia ◽

Defense Responses ◽

Microbial Interactions ◽

Opportunistic Pathogens ◽

Burkholderia Gladioli ◽

Redox Active ◽

Wide Range ◽

Genes Encoding

ABSTRACTBacterial opportunistic pathogens make a wide range of secondary metabolites both in the natural environment and when causing infections, yet how these molecules mediate microbial interactions and their consequences for antibiotic treatment are still poorly understood. Here, we explore the role of two redox-active secondary metabolites, pyocyanin and toxoflavin, as interspecies modulators of antibiotic resilience. We find that these molecules dramatically change susceptibility levels of diverse bacteria to clinical antibiotics. Pyocyanin is made by Pseudomonas aeruginosa, while toxoflavin is made by Burkholderia gladioli, organisms that infect cystic fibrosis and other immunocompromised patients. Both molecules alter the susceptibility profile of pathogenic species within the “Burkholderia cepacia complex” to different antibiotics, either antagonizing or potentiating their effects, depending on the drug’s class. Defense responses regulated by the redox-sensitive transcription factor SoxR potentiate the antagonistic effects these metabolites have against fluoroquinolones, and the presence of genes encoding SoxR and the efflux systems it regulates can be used to predict how these metabolites will affect antibiotic susceptibility of different bacteria. Finally, we demonstrate that inclusion of secondary metabolites in standard protocols used to assess antibiotic resistance can dramatically alter the results, motivating the development of new tests for more accurate clinical assessment.

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Occurrence of Aflatoxins in Rice Intended for Infant Flour Production in Ouagadougou, Burkina Faso

Journal of Advances in Microbiology ◽

10.9734/jamb/2021/v21i1030393 ◽

2021 ◽

pp. 55-66

Author(s):

Hamidou Compaoré ◽

Serge Samandoulougou ◽

Clarisse S. Compaoré ◽

Alima Bambara ◽

Hissein Ratongué ◽

...

Keyword(s):

Aspergillus Flavus ◽

High Performance ◽

Fluorescence Emission ◽

Ultra Violet ◽

Aflatoxin Production ◽

Chemistry Laboratory ◽

Aspergillus Section Flavi ◽

Aflatoxin B2 ◽

Flour Production ◽

Aspergillus Section

A total of four samples of rice intended for infant flour production in Ouagadougou were received at the Physico-chemistry laboratory of Food Technology Department (DTA) for quality control. The latter were also tested for Aspergillus section Flavi presence and analyzed for aflatoxins B1, B2, G1 and G2 content using high performance liquid chromatography (HPLC). Among the twenty (20) strains of mold isolated from these samples, three Aspergillus section Flavi were obtained and cultivated in “Aspergillus flavus and parasiticus Agar (AFPA)” to ascertain if they belong to Aspergillus flavus or Aspergillus parasiticus species. The qualitative ability of aflatoxin production was also performed by fluorescence emission under ultra violet light at 365 nm after four days of incubation at 30 °C on Coconut Agar Medium (CAM). Statistical analysis results showed that 75% of samples were contaminated with total aflatoxins (AFs) with contents ranging from 0.54 ± 0.06 to 2.40 ± 0.07 µg/Kg. Aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) were detected in two contaminated samples. AFB1 had the highest concentration as compared with other aflatoxins. A significant level of contamination (p< 0.0001) was observed in sample R441 compared to other sample types.

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Occurrence and Identification of Aspergillus Section Flavi in the Context of the Emergence of Aflatoxins in French Maize

Toxins ◽

10.3390/toxins10120525 ◽

2018 ◽

Vol 10 (12) ◽

pp. 525 ◽

Cited By ~ 4

Author(s):

Sylviane Bailly ◽

Anwar Mahgubi ◽

Amaranta Carvajal-Campos ◽

Sophie Lorber ◽

Olivier Puel ◽

...

Keyword(s):

Global Warming ◽

Secondary Metabolites ◽

Climatic Conditions ◽

Special Focus ◽

Climate Conditions ◽

Aspergillus Section Flavi ◽

Maize Field ◽

Hot Climate ◽

Field Samples ◽

Aspergillus Section

Aflatoxins (AFs) are secondary metabolites produced by Aspergillus section Flavi during their development, particularly in maize. It is widely accepted that AFB1 is a major contaminant in regions where hot climate conditions favor the development of aflatoxigenic species. Global warming could lead to the appearance of AFs in maize produced in Europe. This was the case in 2015, in France, when the exceptionally hot and dry climatic conditions were favorable for AF production. Our survey revealed AF contamination of 6% (n = 114) of maize field samples and of 15% (n = 81) of maize silo samples analyzed. To understand the origin of the contamination, we characterized the mycoflora in contaminated samples and in samples produced in the same geographic and climatic conditions but with no AFs. A special focus was placed on Aspergillus section Flavi. A total of 67 strains of Aspergillus section Flavi were isolated from the samples. As expected, the strains were observed in all AF+ samples and, remarkably, also in almost 40% of AF− samples, demonstrating the presence of these potent toxin producers in fields in France. A. flavus was the most frequent species of the section Flavi (69% of the strains). But surprisingly, A. parasiticus was also a frequent contaminant (28% of the strains), mostly isolated from AF+ samples. This finding is in agreement with the presence of AFG in most of those samples.

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Aflatoxin in Chili Peppers in Nigeria: Extent of Contamination and Control Using Atoxigenic Aspergillus flavus Genotypes as Biocontrol Agents

Toxins ◽

10.3390/toxins11070429 ◽

2019 ◽

Vol 11 (7) ◽

pp. 429 ◽

Cited By ~ 9

Author(s):

Chibundu N. Ezekiel ◽

Alejandro Ortega-Beltran ◽

Eniola O. Oyedeji ◽

Joseph Atehnkeng ◽

Philip Kössler ◽

...

Keyword(s):

Aspergillus Flavus ◽

Human Exposure ◽

International Markets ◽

Biocontrol Agents ◽

Sub Saharan Africa ◽

Aspergillus Section Flavi ◽

Sub Saharan ◽

Chili Peppers ◽

And Control ◽

Aspergillus Section

Across sub-Saharan Africa, chili peppers are fundamental ingredients of many traditional dishes. However, chili peppers may contain unsafe aflatoxin concentrations produced by Aspergillus section Flavi fungi. Aflatoxin levels were determined in chili peppers from three states in Nigeria. A total of 70 samples were collected from farmers’ stores and local markets. Over 25% of the samples contained unsafe aflatoxin concentrations. The chili peppers were associated with both aflatoxin producers and atoxigenic Aspergillus flavus genotypes. Efficacy of an atoxigenic biocontrol product, Aflasafe, registered in Nigeria for use on maize and groundnut, was tested for chili peppers grown in three states. Chili peppers treated with Aflasafe accumulated significantly less aflatoxins than nontreated chili peppers. The results suggest that Aflasafe is a valuable tool for the production of safe chili peppers. Use of Aflasafe in chili peppers could reduce human exposure to aflatoxins and increase chances to commercialize chili peppers in premium local and international markets. This is the first report of the efficacy of any atoxigenic biocontrol product for controlling aflatoxin in a spice crop.

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A reappraisal of fungi producing aflatoxins

World Mycotoxin Journal ◽

10.3920/wmj2008.1094 ◽

2009 ◽

Vol 2 (3) ◽

pp. 263-277 ◽

Cited By ~ 73

Author(s):

J. Varga ◽

J. Frisvad ◽

R. Samson

Keyword(s):

Secondary Metabolites ◽

Biosynthetic Pathway ◽

Aflatoxin Production ◽

Aspergillus Species ◽

Aflatoxin Biosynthesis ◽

Aspergillus Section Flavi ◽

Naturally Occurring ◽

Aflatoxin B ◽

Aspergillus Section

Aflatoxins are decaketide-derived secondary metabolites which are produced by a complex biosynthetic pathway. Aflatoxins are among the economically most important mycotoxins. Aflatoxin B1 exhibits hepatocarcinogenic and hepatotoxic properties, and is frequently referred to as the most potent naturally occurring carcinogen. Acute aflatoxicosis epidemics occur in several parts of Asia and Africa leading to the death of several hundred people. Aflatoxin production has incorrectly been claimed for a long list of Aspergillus species and also for species assigned to other fungal genera. Recent data indicate that aflatoxins are produced by 13 species assigned to three sections of the genus Aspergillus: section Flavi (A. flavus, A. pseudotamarii, A. parasiticus, A. nomius, A. bombycis, A. parvisclerotigenus, A. minisclerotigenes, A. arachidicola), section Nidulantes (Emericella astellata, E. venezuelensis, E. olivicola) and section Ochraceorosei (A. ochraceoroseus, A. rambellii). Several species claimed to produce aflatoxins have been synonymised with other aflatoxin producers, including A. toxicarius (=A. parasiticus), A. flavus var. columnaris (=A. flavus) or A. zhaoqingensis (=A. nomius). Compounds with related structures include sterigmatocystin, an intermediate of aflatoxin biosynthesis produced by several Aspergilli and species assigned to other genera, and dothistromin produced by a range of non-Aspergillus species. In this review, we wish to give an overview of aflatoxin production including the list of species incorrectly identified as aflatoxin producers, and provide short descriptions of the 'true' aflatoxin producing species.

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