Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.036
Filtrar
1.
Food Chem ; 293: 472-478, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151636

RESUMO

Water activity (aw) and temperature are two pivotal environmental factors affecting Aspergillus flavus growth and aflatoxin production. Here, we found that AFB1 production on polished rice can occur over a wider range of temperature × aw levels than that on paddies. For fungal growth on polished rice, the optimum conditions were aw 0.92-0.96 and 28-37 °C. The maximum amounts of AFB1 on polished rice was observed at 33 °C and aw 0.96. Compared to 33 °C, all tested genes of A. flavus on polished rice were significantly up-regulated at 25 °C under aw 0.96. The late structural genes of pathway were significantly down-regulated at 37 °C under aw 0.96, although aflR and aflS and most of early structural genes were up-regulated. Compared to aw 0.96, most of pathway genes were significantly down-regulated at aw 0.90 and 0.99 under 33 °C, although two regulatory genes were up-regulated at aw 0.90.


Assuntos
Aflatoxinas/biossíntese , Aspergillus flavus/metabolismo , Aflatoxinas/análise , Aspergillus flavus/genética , Aspergillus flavus/crescimento & desenvolvimento , Cromatografia Líquida de Alta Pressão , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Oryza/microbiologia , Temperatura Ambiente , Água/química , Água/metabolismo
2.
J Agric Food Chem ; 67(22): 6212-6221, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31099566

RESUMO

Common soil fungi, Aspergillus flavus and Aspergillus parasiticus, are opportunistic pathogens that invade preharvest peanut seeds. These fungi often produce carcinogenic aflatoxins that pose a threat to human and animal health through food chains and cause significant economic losses worldwide. Detection of aflatoxins and further processing of crops are mandated to ensure that contaminated agricultural products do not enter food channels. Under favorable conditions, the fungus-challenged peanut seeds produce phytoalexins, structurally related stilbenoids, capable of retarding fungal development. The purpose of the present study was to evaluate the potential influence of peanut phytoalexins on fungal development and aflatoxin formation in the course of peanut-fungus interaction. The present research revealed that during such interaction, aflatoxin formation was completely suppressed in A. flavus and A. parasiticus strains tested, when low concentrations of spores were introduced to wounded preincubated peanuts. In most of the experiments, when fungal spore concentrations were 2 orders of magnitude higher, the spores germinated and produced aflatoxins. Of all experimental seeds that showed fungal growth, 57.7% were aflatoxin-free after 72 h of incubation. The research provided new knowledge on the aflatoxin/phytoalexin formation in the course of peanut-fungus interaction.


Assuntos
Aflatoxinas/biossíntese , Arachis/microbiologia , Aspergillus/metabolismo , Sementes/química , Estilbenos/farmacologia , Arachis/química , Arachis/metabolismo , Aspergillus/efeitos dos fármacos , Aspergillus/crescimento & desenvolvimento , Interações Hospedeiro-Parasita , Doenças das Plantas/microbiologia , Sementes/metabolismo , Sementes/microbiologia , Sesquiterpenos/metabolismo , Sesquiterpenos/farmacologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/metabolismo , Estilbenos/metabolismo
3.
Mol Plant Microbe Interact ; 32(9): 1210-1228, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30986121

RESUMO

Histone deacetylases (HDACs) always function as corepressors and sometimes as coactivators in the regulation of fungal development and secondary metabolite production. However, the mechanism through which HDACs play positive roles in secondary metabolite production is still unknown. Here, classical HDAC enzymes were identified and analyzed in Aspergillus flavus, a fungus that produces one of the most carcinogenic secondary metabolites, aflatoxin B1 (AFB1). Characterization of the HDACs revealed that a class I family HDAC, HosA, played crucial roles in growth, reproduction, the oxidative stress response, AFB1 biosynthesis, and pathogenicity. To a lesser extent, a class II family HDAC, HdaA, was also involved in sclerotia formation and AFB1 biosynthesis. An in vitro analysis of HosA revealed that its HDAC activity was considerably diminished at nanomolar concentrations of trichostatin A. Notably, chromatin immunoprecipitation experiments indicated that HosA bound directly to AFB1 biosynthesis cluster genes to regulate their expression. Finally, we found that a transcriptional regulator, SinA, interacts with HosA to regulate fungal development and AFB1 biosynthesis. Overall, our results reveal a novel mechanism by which classical HDACs mediate the induction of secondary metabolite genes in fungi.


Assuntos
Aflatoxinas , Aspergillus flavus , Regulação Fúngica da Expressão Gênica , Histona Desacetilases , Aflatoxinas/biossíntese , Aflatoxinas/genética , Aspergillus flavus/enzimologia , Aspergillus flavus/genética , Aspergillus flavus/patogenicidade , Regulação Fúngica da Expressão Gênica/genética , Histona Desacetilases/genética , Histona Desacetilases/metabolismo , Ligação Proteica , Virulência/genética
4.
Food Microbiol ; 82: 269-276, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31027783

RESUMO

Dry-cured meat products, such as dry-cured ham or dry-fermented sausages, are characterized by their particular ripening process, where a mould population grows on their surface. Some of these moulds are hazardous to the consumers because of their ability to produce mycotoxins including aflatoxins (AFs). The use of native yeasts could be considered a potential strategy for controlling the presence of AFs in dry-cured meat products. The aim of this work was to evaluate the antagonistic activity of two native Debaryomyces hansenii strains on the relative growth rate and the AFs production in Aspergillus parasiticus. Both D. hansenii strains significantly reduced the growth rates of A. parasiticus when grown in a meat-model system at different water activity (aw) conditions. The presence of D. hansenii strains caused a stimulation of AFs production by A. parasiticus at 0.99 aw. However, at 0.92 aw the yeasts significantly reduced the AFs concentration in the meat-model system. The relative expression levels of the aflR and aflS genes involved in the AFs biosynthetic pathway were also repressed at 0.92 aw in the presence of both D. hansenii strains. These satisfactory results were confirmed in dry-cured ham and dry-fermented sausage slices inoculated with A. parasiticus, since both D. hansenii strains significantly reduced AFs amounts in these matrices. Therefore, both tested D. hansenii strains could be proposed as biocontrol agents within a HACCP framework to minimize the hazard associated with the presence of AFs in dry-cured meat products.


Assuntos
Aflatoxinas/biossíntese , Aspergillus/metabolismo , Agentes de Controle Biológico , Debaromyces/fisiologia , Produtos da Carne/microbiologia , Aflatoxinas/genética , Antibiose , Aspergillus/crescimento & desenvolvimento , Regulação para Baixo , Microbiologia de Alimentos , Produtos da Carne/análise , Água/análise
5.
Appl Microbiol Biotechnol ; 103(11): 4623-4632, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30997552

RESUMO

Recent studies from our laboratory indicate that engineered silver nanoparticles can inhibit aflatoxin biosynthesis even at concentrations at which they do not demonstrate antifungal activities on the aflatoxin-producing fungus. Whether such inhibition can be modified by altering the nanoparticles' physical properties remains unclear. In this study, we demonstrate that three differently sized citrated-coated silver nanoparticles denoted here as NP1, NP2, and NP3 (where, sizes of NP1 < NP2 < NP3) inhibit aflatoxin biosynthesis at different effective doses in Aspergillus parasiticus, the plant pathogenic filamentous fungus. Recapping NP2 with polyvinylpyrrolidone coating (denoted here as NP2p) also altered its ability to inhibit aflatoxin production. Dose-response experiments with NP concentrations ranging from 10 to 100 ng mL-1 indicated a non-monotonic relationship between aflatoxin inhibition and NP concentration. The maximum inhibitory concentrations differed between the NP types. NP1 demonstrated maximum inhibition at 25 ng mL-1. Both NP2 and NP3 showed maximum inhibition at 50 ng mL-1, although NP2 resulted in a significantly higher inhibition than NP3. While both NP2 and NP2p demonstrated greater aflatoxin inhibition than NP1 and NP3, NP2p inhibited aflatoxin over a significantly wider concentration range as compared to NP2. Our results, therefore, suggest that nano-fungal interactions can be regulated by altering certain NP physical properties. This concept can be used to design NPs for mycotoxin prevention optimally.


Assuntos
Aflatoxinas/antagonistas & inibidores , Aflatoxinas/biossíntese , Antifúngicos/metabolismo , Aspergillus/efeitos dos fármacos , Metabolismo/efeitos dos fármacos , Nanopartículas Metálicas/química , Prata/metabolismo , Aspergillus/crescimento & desenvolvimento , Aspergillus/metabolismo , Nanopartículas Metálicas/ultraestrutura , Venenos
6.
Bioengineered ; 10(1): 13-22, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-30836830

RESUMO

The deep-sea bacterium strain FA13 was isolated from the sediment of the South Atlantic Ocean and identified as Bacillus circulans based on 16S ribosomal DNA sequence. Through liquid fermentation with five media, the cell-free supernatant fermented with ISP2 showed the highest inhibition activities against mycelial growth of Aspergillus parasiticus mutant strain NFRI-95 and accumulation of norsolorinic acid, a precursor for aflatoxin production. Based on ISP2, uniform design was used to optimize medium formula and fermentation conditions. After optimization, the inhibition efficacy of the 20-time diluted supernatant against A. parasiticus NFRI-95 mycelial growth and aflatoxin production was increased from 0-23.1% to 100%. Moreover, compared to the original protocol, medium cost and fermentation temperature were significantly reduced, and dependence on seawater was completely relieved, thus preventing the fermentor from corrosion. This is the first report of a deep-sea microorganism which can inhibit A. parasiticus NFRI-95 mycelial growth and aflatoxin production.


Assuntos
Aflatoxinas/antagonistas & inibidores , Antraquinonas/antagonistas & inibidores , Antitoxinas/isolamento & purificação , Aspergillus/efeitos dos fármacos , Bacillus/metabolismo , Micélio/efeitos dos fármacos , Aflatoxinas/biossíntese , Antraquinonas/metabolismo , Antitoxinas/farmacologia , Organismos Aquáticos , Aspergillus/crescimento & desenvolvimento , Aspergillus/metabolismo , Aspergillus/patogenicidade , Oceano Atlântico , Bacillus/classificação , Bacillus/genética , Bacillus/isolamento & purificação , Reatores Biológicos , Meios de Cultura/química , Análise Fatorial , Fermentação , Sedimentos Geológicos/microbiologia , Micélio/crescimento & desenvolvimento , Micélio/metabolismo , Micélio/patogenicidade , Filogenia , RNA Ribossômico 16S/genética , Temperatura Ambiente
7.
Int J Biol Macromol ; 131: 420-434, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30831165

RESUMO

Here, we studied the preparation, characterization, anti-aflatoxigenic activity, and molecular mechanism in vitro of chitosan packaging films containing turmeric essential oil (TEO). First, we took the mechanical properties as the evaluation Index, screened for the optimum preparation conditions of packaging films with 1.5 µL/cm2 TEO using single factor and orthogonal experiments, and characterized the film properties. We found that the addition of TEO affected the microcosmic structure of films and advanced water resistance capacity. In addition, we investigated the inhibitory effects of pure chitosan films and packaging films containing 1.5 µL/cm2 or 3.0 µL/cm2 TEO on the growth and conidial formation of Aspergillus flavus (A. flavus, CGMCC 3.4410), as well as the accumulation of aflatoxin over the course of seven days. We found that the packaging films possessed a prominent antifungal activity on A. flavus. Finally, we discuss preliminary results surrounding gene expression of packaging films which inhibit aflatoxin biosynthesis. The expressions levels of 16 genes related to aflatoxin biosynthesis were found to be either completely or almost completely inhibited. Therefore, the addition of the natural antifungal agent TEO in chitosan packaging films represent a remarkable method to significantly promote the development and application of antifungal packaging materials.


Assuntos
Aflatoxinas/antagonistas & inibidores , Antifúngicos/química , Antifúngicos/farmacologia , Quitosana/química , Curcuma/química , Óleos Voláteis/química , Aflatoxinas/biossíntese , Aspergillus flavus/efeitos dos fármacos , Aspergillus flavus/genética , Aspergillus flavus/metabolismo , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Fenômenos Químicos , Embalagem de Alimentos , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Modelos Biológicos , Peso Molecular , Óleos Voláteis/isolamento & purificação , Permeabilidade , Extratos Vegetais/química , Solubilidade , Análise Espectral , Vapor , Temperatura Ambiente
8.
J Agric Food Chem ; 67(15): 4200-4213, 2019 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-30916945

RESUMO

In Aspergillus, the cyclic adenosine monophosphate (cAMP) signaling modulates asexual development and mycotoxin biosynthesis. Here, we characterize the cyclase-associated protein Cap in the pathogenic fungus Aspergillus flauvs. The cap disruption mutant exhibited dramatic reduction in hyphal growth, conidiation, and spore germination, while an enhanced production of the sclerotia was observed in this mutant. Importantly, the cap gene was found to be important for mycotoxin biosynthesis and virulence. The domain deletion study demonstrated that each domain played an important role for the Cap protein in regulating cAMP/protein kinase A (PKA) signaling, while only P1 and CARP domains were essential for the full function of Cap. The phosphorylation of Cap at S35 was identified in A. flavus, which was found to play a negligible role for the function of Cap. Overall, our results indicated that Cap with multiple domains engages in mycotoxin production and fungal pathogenicity, which could be designed as potential control targets for preventing this fungal pathogen.


Assuntos
Aflatoxinas/biossíntese , Aspergillus flavus/metabolismo , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismo , Aspergillus flavus/enzimologia , Aspergillus flavus/genética , Aspergillus flavus/patogenicidade , AMP Cíclico/metabolismo , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica , Doenças das Plantas/microbiologia , Domínios Proteicos , Esporos Fúngicos/enzimologia , Esporos Fúngicos/genética , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/metabolismo , Virulência , Zea mays/microbiologia
9.
J Basic Microbiol ; 59(6): 599-608, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30900741

RESUMO

Aflatoxins are part of fungal secondary metabolites which become serious health, environmental, and economic problems and can cause corruption of many crops and agricultural grains that used as food and feed for human and animal. Aflatoxins mainly produce by Aspergillus spp. especially Aspergillus flavus and Aspergillus parasiticus. The present work aimed to study the effect of nanoencapsulation of chitosan (CS) nanoparticles with two phenolic compounds 1-(2-ethyl,6-heptyl)phenol (EHP) extracted from Cuminum cyminum and 5-ethyl-2-(methoxymethyl)phenol (EMMP) extracted from black pepper on growth and aflatoxins production of A. flavus and A. parasiticus. A. flavus growth was completely inhibited by 0.6 mg/ml of EHP and EMMP as well as A. parasiticus which showed the same minimal inhibition concentration with the first compound and 0.8 mg/ml with the second one. CS nanoparticles inhibited the growth of the tested organisms more than CS especially with A. parasiticus and this potency became much better when nanoencapsulated with the two extracted phenolic compounds. In inhibition of aflatoxins production, EHP reduced the production of aflatoxin B1 and B2 of A. flavus by 68.6% and 69.7%, respectively. In the same manner EMMP reduce the production of the two toxins by 87.3% and 82.6%, respectively. The reduction effect of CS nanoparticles is much more than that of CS as it record in most cases about twofold increase. Nanoencapsulation of CS nanoparticles by the extracted phenolic compounds is much more effective with complete inhibition of aflatoxin B1 of both fungi and aflatoxin G1 of A. parasiticus.


Assuntos
Aflatoxinas/biossíntese , Aspergillus/crescimento & desenvolvimento , Aspergillus/metabolismo , Quitosana/química , Nanopartículas/química , Fenóis/química , Aspergillus/efeitos dos fármacos , Aspergillus flavus/efeitos dos fármacos , Aspergillus flavus/crescimento & desenvolvimento , Aspergillus flavus/metabolismo , Quitosana/farmacologia , Cuminum/química , Estrutura Molecular , Nanopartículas/toxicidade , Fenóis/isolamento & purificação , Fenóis/farmacologia , Piper nigrum/química
10.
J Appl Microbiol ; 126(4): 1257-1264, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30548988

RESUMO

AIMS: Field control of aflatoxin contamination is thought to occur through competitive exclusion of native aflatoxigenic fungi by introduced nonaflatoxigenic Aspergillus flavus biocontrol strains. In this study, we explored another possible mechanism that could increase the efficacy of biocontrol strains-the production of secreted compounds termed extrolites. METHODS AND RESULTS: Using four Aspergillus strains (one nonaflatoxigenic and three aflatoxigenic) from the same geographic region (Louisiana), we devised experiments whereby each aflatoxigenic strain was grown on media that had first been colonized by the nonaflatoxigenic strain. We observed noticeable reduction in growth and reduced production of aflatoxin and cyclopiazonic acid for all three aflatoxigenic strains when grown in the presence of extrolite secretions from the nonaflatoxigenic strain. CONCLUSIONS: We provide evidence that biocontrol strain extrolites may improve the efficacy of pre and postharvest aflatoxin reduction. SIGNIFICANCE AND IMPACT OF THE STUDY: Our finding, that extrolites secreted by nonaflatoxigenic A. flavus strains potentially abate growth and toxin levels of aflatoxin-producing strains, should allow for us to elucidate the mechanism of how the reduction in toxigenic strains occurs, and potentially identify better biocontrol strains. Identification and isolation of the active extrolites may afford a supplemental method to mitigate aflatoxin production.


Assuntos
Aflatoxinas/biossíntese , Aspergillus flavus/metabolismo , Agentes de Controle Biológico/farmacologia , Antibiose , Aspergillus/efeitos dos fármacos , Aspergillus/crescimento & desenvolvimento , Aspergillus/metabolismo , Meios de Cultura/química , Indóis/metabolismo
11.
Lett Appl Microbiol ; 68(2): 104-111, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30554415

RESUMO

Inhibition of Aspergillus flavus growth and its aflatoxins production using the biocontrol agent Saccharomyces cerevisiae as well as to explore its mode of action was studied. Eight strains of S. cerevisiae strains were able to suppress the growth of A. flavus Z103. The maximum growth inhibition of A. flavus Z103 was obtained by living cells of S. cerevisiae EBF101 and S. cerevisiae 117 with 85 and 83%, respectively. The sporulation inhibition and hyphae deterioration of A. flavus Z103 by S. cerevisiae cells adhesion were observed under SEM; up to 99·8% inhibition of aflatoxins biosynthesis by A. flavus Z103 was resulted when the fungus was treated by autoclaved extracellular crude of S. cerevisiae. Also, the tested strains are potential to produce exo-chitinase which could be suggested as another mode of action for its antifungal activity. GC-MS analysis of S. cerevisiae 117 extracellular secondary metabolites revealed the existence of 4-Hydroxyphenethyl alcohol (46·32%), 4, 4-Dimethyloxazole (9·14%) and 1,2-Benzenedicarboxylic acid dioctyl ester (2·8%). Significance and Impact of the Study: The use of Saccharomyces cerevisiae instead of chemical preservatives in fermented food, animal and fish feed and storage cereal grains could encourage the food industry to produce organic food free of chemical additives. Overall, our data suggest the possibility of using S. cerevisiae as an alternative treatment in the food industries to control the dispersion and aflatoxins production by Aspergillus flavus during storage. This method could provide an additional probiotic effect in the digestive tract of consumers after ingestion of the treated food. So, our study clarifies the exact mechanisms responsible for the reduction of the aflatoxin contents by S. cerevisiae.


Assuntos
Aflatoxinas/biossíntese , Aspergillus flavus/crescimento & desenvolvimento , Aspergillus flavus/metabolismo , Agentes de Controle Biológico/metabolismo , Saccharomyces cerevisiae/metabolismo , Esporos Fúngicos/crescimento & desenvolvimento , Animais , Hexosaminidases/metabolismo , Hifas/metabolismo , Saccharomyces cerevisiae/classificação , Saccharomyces cerevisiae/enzimologia
12.
Int J Food Microbiol ; 292: 91-100, 2019 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-30584973

RESUMO

Aspergilli are common contaminants of food and feed and a major source of mycotoxins. In this study, 87 Aspergillus strains were isolated from beans from 14 different cities in Brazil and identified to the species level based on partial calmodulin and ß-tubulin sequence data. All green spored isolates belonged to section Flavi and were identified as A. flavus (n = 39) or A. pseudocaelatus (n = 1). All black spored isolates belonged to section Nigri and were identified as A. niger (n = 24) or A. luchuensis (n = 10), while the yellow spored strains were identified as A. westerdijkiae (n = 7), A. ostianus (n = 3), A. ochraceus (n = 1) or A. wentii (n = 2). The toxigenic potential of these Aspergillus strains from beans was studied by the prospection of genes in three of the major mycotoxin clusters: aflatoxin (seven genes checked), ochratoxin A (four genes) and fumonisin (ten genes and two intergenic regions). Genes involved in the biosynthesis of aflatoxin were only detected in A. flavus isolates: 17/39 A. flavus isolates proved to contain all the aflatoxin genes tested, the others missed one or more genes. The full complement of fumonisin biosynthesis genes was identified in all A. niger isolates. Finally, no genes for ochratoxin A were detected in any of the isolates. Our work suggests that aflatoxin production by some A. flavus strains and fumonisin production by A. niger isolates form the largest mycotoxin risks in Brazilian beans.


Assuntos
Aspergillus/classificação , Fabaceae/microbiologia , Proteínas Fúngicas/genética , Aflatoxinas/biossíntese , Sequência de Aminoácidos , Aspergillus/genética , Aspergillus/isolamento & purificação , Brasil , DNA Fúngico/isolamento & purificação , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Fumonisinas/metabolismo , Família Multigênica , Micotoxinas/biossíntese , Ocratoxinas/biossíntese , Análise de Sequência de DNA
13.
Int J Food Microbiol ; 284: 11-21, 2018 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-29990635

RESUMO

In Aspergillus flavus, laeA affects cell morphology and contributes to the production of secondary metabolites (SMs) production including aflatoxin, cyclopiazonic acid, and aflatrem. Here, we investigated the function of this transcription factor by performing proteomics analysis of the wild-type (WT) and ΔlaeA mutant growing on corn. Notably, our proteomics profile confirmed the functions of extracellular hydrolases, conidial hydrophobin, and response to oxidative stress during the induction of aflatoxin biosynthesis regulated by laeA. Unexpectedly, deletion of laeA resulted in the significant upregulation of the NAD+-dependent histone deacetylase sirA involved in silencing SM clusters via chromatin remodeling. Accompanying the chromatin modification, enzymes participating in SM, including aflatoxin and cyclopiazonic acid biosynthesis, were drastically decreased. Another unexpected finding was that enzymes in the recently identified ustiloxin B biosynthesis pathway might be regulated by laeA. These data provided novel insights into the complex regulation of laeA and suggested a potential link between laeA deletion, NAD+-dependent histone deacetylation, and SM production in A. flavus.


Assuntos
Aspergillus flavus/metabolismo , Regulação Fúngica da Expressão Gênica/genética , Metiltransferases/biossíntese , Metiltransferases/genética , Fatores de Transcrição/biossíntese , Aflatoxinas/biossíntese , Aspergillus flavus/genética , Montagem e Desmontagem da Cromatina/genética , Proteínas Fúngicas/genética , Perfilação da Expressão Gênica , Histona Desacetilases/biossíntese , Hidrolases/genética , Hidrolases/metabolismo , Indóis/metabolismo , Estresse Oxidativo/fisiologia , Peptídeos Cíclicos/biossíntese , Proteômica , Esporos Fúngicos/metabolismo , Fatores de Transcrição/genética , Zea mays/microbiologia
14.
Int J Food Microbiol ; 282: 9-15, 2018 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-29885975

RESUMO

Peanuts are widely consumed as the main ingredient in many local dishes in Malaysia. However, the tropical climate in Malaysia (high temperature and humidity) favours the growth of fungi from Aspergillus section Flavi, especially during storage. Most of the species from this section, such as A. flavus, A. parasiticus and A. nomius, are natural producers of aflatoxins. Precise identification of local isolates and information regarding their ability to produce aflatoxins are very important to evaluate the safety of food marketed in Malaysia. Therefore, this study aimed to identify and characterize the aflatoxigenic and non-aflatoxigenic strains of Aspergillus section Flavi in peanuts and peanut-based products. A polyphasic approach, consisting of morphological and chemical characterizations was applied to 128 isolates originating from raw peanuts and peanut-based products. On the basis of morphological characters, 127 positively identified as Aspergillus flavus, and the other as A. nomius. Chemical characterization revealed six chemotype profiles which indicates diversity of toxigenic potential. About 58.6%, 68.5%, and 100% of the isolates are positive for aflatoxins, cyclopiazonic acid and aspergillic acid productions respectively. The majority of the isolates originating from raw peanut samples (64.8%) were aflatoxigenic, while those from peanut-based products were less toxigenic (39.1%). The precise identification of these species may help in developing control strategies for aflatoxigenic fungi and aflatoxin contamination in peanuts, especially during storage. These findings also highlight the possibility of the co-occurrence of other toxins, which could increase the potential toxic effects of peanuts.


Assuntos
Aflatoxinas/biossíntese , Arachis/microbiologia , Aspergillus/isolamento & purificação , Contaminação de Alimentos/análise , Arachis/química , Aspergillus/classificação , Aspergillus/genética , Aspergillus/metabolismo , Aspergillus flavus/isolamento & purificação , Malásia , Sementes/química , Sementes/microbiologia
15.
Shokuhin Eiseigaku Zasshi ; 59(1): 45-50, 2018.
Artigo em Japonês | MEDLINE | ID: mdl-29743467

RESUMO

Aspergillus parasiticus contamination of peanuts results in the production of highly toxic metabolites, such as aflatoxin B1, B2, G1 and G2, and its incidence in imported peanuts is reported to be increasing. Here, we examined whether the antifungal compound allyl isothiocyanate (AIT), which is present in mustard seed, could inhibit the growth of seed-borne fungi and aflatoxin-producing fungi. Peanuts produced in China and Japan were inoculated with A. parasiticus and exposed to AIT vapor released by a commercial mustard seed extract in closed containers under controlled conditions of temperature and humidity. AIT in the inoculated peanut samples reached its highest concentration of 44.8 ng/mL at 3 hr and decreased to 5.6 ng/mL after 9 weeks. Although AIT decreased the growth of the seed-borne fungi during the test period, the inoculated fungi survived. All tested peanuts samples were analyzed for aflatoxin using the HPLC method. There was a correlation between the number of aflatoxin-producing fungi and the total amount of aflatoxin production in the inoculated peanut samples. Our results indicate that AIT was effective in inhibiting the growth of seed-borne fungi and aflatoxin-producing fungi.


Assuntos
Aflatoxinas/análise , Aflatoxinas/biossíntese , Compostos Alílicos , Antifúngicos , Arachis/química , Arachis/microbiologia , Aspergillus/crescimento & desenvolvimento , Aspergillus/metabolismo , Cromatografia Líquida de Alta Pressão/métodos , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Contaminação de Alimentos/prevenção & controle , Armazenamento de Alimentos/métodos , Isocianatos , Compostos Alílicos/farmacologia , Antifúngicos/farmacologia , Depressão Química , Isocianatos/farmacologia , Mostardeira , Sementes , Volatilização
16.
J Microbiol ; 56(5): 356-364, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29721833

RESUMO

Aspergillus flavus often invade many important corps and produce harmful aflatoxins both in preharvest and during storage stages. The regulation mechanism of aflatoxin biosynthesis in this fungus has not been well explored mainly due to the lack of an efficient transformation method for constructing a genome-wide gene mutant library. This challenge was resolved in this study, where a reliable and efficient Agrobacterium tumefaciens-mediated transformation (ATMT) protocol for A. flavus NRRL 3357 was established. The results showed that removal of multinucleate conidia, to collect a homogenous sample of uninucleate conidia for use as the transformation material, is the key step in this procedure. A. tumefaciens strain AGL-1 harboring the ble gene for zeocin resistance under the control of the gpdA promoter from A. nidulans is suitable for genetic transformation of this fungus. We successfully generated A. flavus transformants with an efficiency of ∼ 60 positive transformants per 106 conidia using our protocol. A small-scale insertional mutant library (∼ 1,000 mutants) was constructed using this method and the resulting several mutants lacked both production of conidia and aflatoxin biosynthesis capacity. Southern blotting analysis demonstrated that the majority of the transformants contained a single T-DNA insert on the genome. To the best of our knowledge, this is the first report of genetic transformation of A. flavus via ATMT and our protocol provides an effective tool for construction of genome-wide gene mutant libraries for functional analysis of important genes in A. flavus.


Assuntos
Aflatoxinas/biossíntese , Aflatoxinas/genética , Agrobacterium tumefaciens/genética , Aspergillus flavus/genética , Transformação Genética , Aflatoxina B1/genética , Aspergillus flavus/citologia , Aspergillus flavus/efeitos dos fármacos , Aspergillus flavus/crescimento & desenvolvimento , Aspergillus nidulans/genética , Bleomicina/farmacologia , DNA Bacteriano/genética , DNA Fúngico , Regulação Fúngica da Expressão Gênica , Genes Fúngicos/genética , Vetores Genéticos , Germinação/efeitos dos fármacos , Mutagênese Insercional/métodos , Fenótipo , Esporos Fúngicos/citologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/genética
17.
Appl Microbiol Biotechnol ; 102(12): 5209-5220, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29696338

RESUMO

Many glycosylphosphatidylinositol-anchored proteins (GPI-APs) of fungi are membrane enzymes, organization components, and extracellular matrix adhesins. We analyzed eight Aspergillus flavus transcriptome sets for the GPI-AP gene family and identified AFLA_040110, AFLA_063860, and AFLA_113120 to be among the top 5 highly expressed genes of the 36 family genes analyzed. Disruption of the former two genes did not drastically affect A. flavus growth and development. In contrast, disruption of AFLA_113120, an orthologue of Saccharomyces cerevisiae ECM33, caused a significant decrease in vegetative growth and conidiation, promoted sclerotial production, and altered conidial pigmentation. The A. flavus ecm33 null mutant, compared with the wild type and the complemented strain, produced predominantly aflatoxin B2 but accumulated comparable amounts of cyclopiazonic acid. It showed decreased sensitivity to Congo red at low concentrations (25-50 µg/mL) but had increased sensitivity to calcofluor white at high concentrations (250-500 µg/mL). Analyses of cell wall carbohydrates indicated that the α-glucan content was decreased significantly (p < 0.05), but the contents of chitin and ß-glucan were increased in the mutant strain. In a maize colonization study, the mutant was shown to be impaired in its infectivity and produced 3- to 4-fold lower amounts of conidia than the wild type and the complemented strain. A. flavus Ecm33 is required for proper cell wall composition and plays an important role in normal fungal growth and development, aflatoxin biosynthesis, and seed colonization.


Assuntos
Aflatoxinas/genética , Aspergillus flavus/fisiologia , Proteínas Fúngicas/genética , Zea mays/microbiologia , Aflatoxinas/biossíntese , Aspergillus flavus/genética , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Esporos Fúngicos/genética , Transcriptoma
18.
J Microbiol ; 56(2): 119-127, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29392555

RESUMO

Important staple foods (peanuts, maize and rice) are susceptible to contamination by aflatoxin (AF)-producing fungi such as Aspergillus flavus. The objective of this study was to explore non-aflatoxin-producing (atoxigenic) A. flavus strains as biocontrol agents for the control of AFs. In the current study, a total of 724 A. flavus strains were isolated from different regions of China. Polyphasic approaches were utilized for species identification. Non-aflatoxin and non-cyclopiazonic acid (CPA)-producing strains were further screened for aflatoxin B1 (AFB1) biosynthesis pathway gene clusters using a PCR assay. Strains lacking an amplicon for the regulatory gene aflR were then analyzed for the presence of the other 28 biosynthetic genes. Only 229 (32%) of the A. flavus strains were found to be atoxigenic. Smaller (S) sclerotial phenotypes were dominant (51%) compared to large (L, 34%) and non-sclerotial (NS, 15%) phenotypes. Among the atoxigenic strains, 24 strains were PCR-negative for the fas-1 and aflJ genes. Sixteen (67%) atoxigenic A. flavus strains were PCRnegative for 10 or more of the biosynthetic genes. Altogether, 18 new PCR product patterns were observed, indicating great diversity in the AFB1 biosynthesis pathway. The current study demonstrates that many atoxigenic A. flavus strains can be isolated from different regions of China. In the future laboratory as well as field based studies are recommended to test these atoxigenic strains as biocontrol agents for aflatoxin contamination.


Assuntos
Aflatoxinas/biossíntese , Aflatoxinas/genética , Aspergillus flavus/genética , Aspergillus flavus/isolamento & purificação , Aspergillus flavus/metabolismo , Genes Fúngicos/genética , Aflatoxina B1/biossíntese , Aflatoxina B1/genética , Aflatoxinas/classificação , Aspergillus flavus/classificação , Agentes de Controle Biológico , China , Produtos Agrícolas/microbiologia , DNA Fúngico/genética , Proteínas de Ligação a DNA/genética , Proteínas Fúngicas/genética , Deleção de Genes , Indóis/metabolismo , Família Multigênica , Reação em Cadeia da Polimerase , Fatores de Transcrição/genética
19.
Artigo em Inglês | MEDLINE | ID: mdl-29338637

RESUMO

Recent research has showed that Aspergillus flavus and Aspergillus parasiticus are aflatoxigenic species that can become very competitive in the framework of climate change. Aflatoxins show carcinogenic, mutagenic, immunotoxic and teratogenic effects on human and animals. Effective and sustainable measures to inhibit these species and aflatoxins in food are required. Origanum vulgare and Cinnamomum zeylanicum essential oils (EOs) and their major active constituents, carvacrol and cinnamaldehyde, respectively, were assayed for inhibiting these species and aflatoxin production in maize extract medium under different environmental conditions. Doses of 10-1000 mg l-1 were assayed and the effective doses for 50 (ED50) and 90% (ED90) growth inhibition were determined. The ED50 of cinnamaldehyde, carvacrol, oregano EO, and cinnamon EO against A. flavus were in the ranges 49-52.6, 98-145, 152-505, 295-560 mg l-1 and against A. parasiticus in the ranges 46-55.5, 101-175, 260-425 and 490-675 mg l-1, respectively, depending on environmental conditions. In A. flavus treatments ED90 were in the ranges 89.7-90.5, 770-860 and 820->1000 mg l-1 for cinnamaldehyde, carvacrol and cinnamon EO, and in A. parasiticus treatments in the ranges 89-91, 855->1000 and 900->1000 mg l-1, respectively. ED90 values for oregano EO against both species were >1000 mg l-1. Growth rates of both species were higher at 37 than at 25°C and at 0.99 than at 0.96 aw. Aflatoxin production was higher at 25 than at 37°C. Stimulation of aflatoxin production was observed at low doses except for cinnamaldehyde treatments. The effectiveness of EOs and their main constituents to inhibit fungal growth and aflatoxin production in contact assays was lower than in vapour phase assays using bioactive EVOH-EO films previously reported.


Assuntos
Aflatoxinas/biossíntese , Antifúngicos/farmacologia , Aspergillus/efeitos dos fármacos , Aspergillus/crescimento & desenvolvimento , Microbiologia de Alimentos , Óleos Voláteis/química , Óleos Voláteis/farmacologia , Acroleína/análogos & derivados , Acroleína/química , Acroleína/isolamento & purificação , Acroleína/farmacologia , Antifúngicos/química , Antifúngicos/isolamento & purificação , Aspergillus/metabolismo , Cinnamomum zeylanicum/química , Testes de Sensibilidade Microbiana , Monoterpenos/química , Monoterpenos/isolamento & purificação , Monoterpenos/farmacologia , Origanum/química
20.
Proc Natl Acad Sci U S A ; 115(4): E753-E761, 2018 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-29317534

RESUMO

The fungal genus of Aspergillus is highly interesting, containing everything from industrial cell factories, model organisms, and human pathogens. In particular, this group has a prolific production of bioactive secondary metabolites (SMs). In this work, four diverse Aspergillus species (A. campestris, A. novofumigatus, A. ochraceoroseus, and A. steynii) have been whole-genome PacBio sequenced to provide genetic references in three Aspergillus sections. A. taichungensis and A. candidus also were sequenced for SM elucidation. Thirteen Aspergillus genomes were analyzed with comparative genomics to determine phylogeny and genetic diversity, showing that each presented genome contains 15-27% genes not found in other sequenced Aspergilli. In particular, A. novofumigatus was compared with the pathogenic species A. fumigatus This suggests that A. novofumigatus can produce most of the same allergens, virulence, and pathogenicity factors as A. fumigatus, suggesting that A. novofumigatus could be as pathogenic as A. fumigatus Furthermore, SMs were linked to gene clusters based on biological and chemical knowledge and analysis, genome sequences, and predictive algorithms. We thus identify putative SM clusters for aflatoxin, chlorflavonin, and ochrindol in A. ochraceoroseus, A. campestris, and A. steynii, respectively, and novofumigatonin, ent-cycloechinulin, and epi-aszonalenins in A. novofumigatus Our study delivers six fungal genomes, showing the large diversity found in the Aspergillus genus; highlights the potential for discovery of beneficial or harmful SMs; and supports reports of A. novofumigatus pathogenicity. It also shows how biological, biochemical, and genomic information can be combined to identify genes involved in the biosynthesis of specific SMs.


Assuntos
Aflatoxinas/genética , Aspergillus/genética , Aspergillus/metabolismo , Família Multigênica , Metabolismo Secundário/genética , Aflatoxinas/biossíntese , Alérgenos/genética , Aspergillus/patogenicidade , Metilação de DNA , Evolução Molecular , Flavonoides/biossíntese , Genoma Fúngico , Alcaloides Indólicos/metabolismo , Filogenia , Terpenos/metabolismo , Sequenciamento Completo do Genoma
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA