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Effects of blasticidin S ( ■ ), blasticidin S carboxymethyl ester (●) and deaminohydroxyblasticidin S (▲) on aflatoxin production by A. flavus IMF 47798 in a YES liquid medium. The amount of aflatoxin B1 in the culture filtrate was quantitated by LC-MS/MS. Data are presented as the mean ± SD (n = 6).
Source publication
Blasticidin S (BcS) is a protein synthesis inhibitor which shows strong growth inhibitory activity against a number of microorganisms. However, BcS inhibited aflatoxin production by Aspergillus flavus without affecting its growth. In order to obtain information about the structure–activity relationship of BcS as an aflatoxin production inhibitor, B...
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Context 1
... the inhibitory activities of BcS, DahBcS, and MeBcS against aflatoxin production by A. flavus IMF 47798 strain in a broth medium containing yeast extract and sucrose (YES medium) were examined. The result is shown in Figure 3. The amount of AFB 1 produced by this strain in YES medium was about 10 times greater than that in PD broth medium. ...
Context 2
... the inhibitory activities of BcS, DahBcS, and MeBcS against aflatoxin production by A. flavus IMF 47798 strain in a broth medium containing yeast extract and sucrose (YES medium) were examined. The result is shown in Figure 3. The amount of AFB1 produced by this strain in YES medium was about 10 times greater than that in PD broth medium. ...
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Aflatoxin contamination of crops is a worldwide problem, and elucidation of the regulatory mechanism of aflatoxin production, for example relative to the oxidative-antioxidative system, is needed. Studies have shown that oxidative stress induced by reactive oxygen species promotes aflatoxin production. However, superoxide has been suggested to have...
This study investigated the aflatoxin contamination of maize kernels for selected temperature, relative humidity, and moisture content levels. Samples of maize kernels at moisture content levels of 14, 15, 16, 18, and 20% (wb) were inoculated with Aspergillus flavus spores and incubated in a climatic test chamber for ten days at 20°C and 30°C, and...
Aspergillus flavus is a saprophytic fungus that may colonize several important crops, including cotton, maize, peanuts and tree nuts. Concomitant with A. flavus colonization is its potential to secrete mycotoxins, of which the most prominent is aflatoxin. Temperature, water activity (aw) and carbon dioxide (CO₂) are three environmental factors show...
Citations
... Numerous efforts have been made to select new Streptomyces strains that are effective against AFB1 contamination, yet none of the studies led to the commercialization of a specific BCA. On the other hand, some antibiotics, such as dioctatin A, blasticidin A, and aflastatins, produced by Streptomyces strains have been demonstrated to inhibit fungal growth and aflatoxin production in A. parasiticus [19][20][21][22]. However, these studies are mainly based on phenotypic analyses, and no comprehensive transcriptomics studies have been carried out. ...
Crop contamination by aflatoxin B1 (AFB1), an Aspergillus-flavus-produced toxin, is frequently observed in tropical and subtropical regions. This phenomenon is emerging in Europe, most likely as a result of climate change. Alternative methods, such as biocontrol agents (BCAs), are currently being developed to reduce the use of chemicals in the prevention of mycotoxin contamination. Actinobacteria are known to produce many bioactive compounds, and some of them can reduce in vitro AFB1 concentration. In this context, the present study aims to analyze the effect of a cell-free supernatant (CFS) from Streptomyces roseolus culture on the development of A. flavus, as well as on its transcriptome profile using microarray assay and its impact on AFB1 concentration. Results demonstrated that in vitro, the S. roseolus CFS reduced the dry weight and conidiation of A. flavus from 77% and 43%, respectively, and was therefore associated with a reduction in AFB1 concentration reduction to levels under the limit of quantification. The transcriptomic data analysis revealed that 5198 genes were differentially expressed in response to the CFS exposure and among them 5169 were downregulated including most of the genes involved in biosynthetic gene clusters. The aflatoxins' gene cluster was the most downregulated. Other gene clusters, such as the aspergillic acid, aspirochlorine, and ustiloxin B gene clusters, were also downregulated and associated with a variation in their concentration, confirmed by LC-HRMS.
... In order to obtain information about the structure-activity relationship of BcS as an aflatoxin production inhibitor, BcS derivatives were prepared and their aflatoxin production inhibitory activities were evaluated 13) . Among five derivatives, blasticidin S carboxymethyl ester, deaminohydroxyblasticidin S, and pyrimidinoblasticidin S showed inhibitory activity, while the others did not 14) . The IC 50 value for aflatoxin production of the carboxymethyl ester derivative was one-fifth of that of BcS although its antimicrobial activity was almost the same. ...
Aflatoxins are a group of secondary metabolites produced by some Aspergillus species, including A. flavus and A. parasiticus, and are detected in many kinds of food such as corn, tree nuts, dried fruit, and spices. Because they are potent mutagens and are liver carcinogens in humans and a wide range of animal species, aflatoxin contamination in crops causes huge economic losses and may constitute a serious health threat. A practical use of compounds which can control aflatoxin production by fungi is expected to be an effective method to prevent aflatoxin contamination in agricultural products. Many kinds of aflatoxin production inhibitors have already been reported, and most of them are derived from plant constituents, microbial metabolites, or synthetic compounds. We have been searching for new aflatoxin production inhibitors among secondary metabolites produced by actinomycetes. In this review, the features of four aflatoxin production inhibitors, blasticidin A, blasticidin S, dioctatin A and polyoxins are introduced.
... Compounds that are able to inhibit mycotoxin production by fungi may be useful for preventing mycotoxin contamination in agricultural products (Sakuda et al. 2016). We reported that blasticidin S and its derivatives inhibited aflatoxin production by A. flavus (Yoshinari et al. 2013(Yoshinari et al. , 2017. The practical use of blasticidin S is considered to be an effective method to reduce aflatoxin contamination in crops. ...
... Among the four purified polyoxins in polyoxin AL water-soluble powder and one commercially available polyoxin, polyoxin A and K showed relatively strong aflatoxin production inhibitory activity. We previously reported that blasticisin S and its methtyl ester derivative had aflatoxin production inhibitory activity and their IC 50 values were 27 and 5 μmol L −1 , respectively (Yoshinari et al. 2013(Yoshinari et al. , 2017. The IC 50 values of polyoxin A and K are similar to these compounds and have strong inhibitory activities compared with other aflatoxin production inhibitors (Holmes et al. 2008). ...
Co-exposure to aflatoxin and fumonisin is a health concern where corn is a staple food, and a method to prevent co-contamination of these mycotoxins in foods is urgently needed. Polyoxins are chitin synthase inhibitors produced by Streptomyces cacaoi var. asoensis. The aflatoxin production inhibitory activity of a commercially available polyoxin D and four polyoxins purified from polyoxin AL water-soluble powder, an agricultural chemical containing polyoxins, was tested. The five polyoxins dose-dependently inhibited aflatoxin production by Aspergillus parasiticus and the IC50 values of polyoxin A, B, D, K and L were 16, 74, 110, 9 and 280 µmol L–1, respectively. Polyoxins also inhibited fumonisin production by Fusarium fujikuroi, and the IC50 values of polyoxin B, D, K and L were 270, 42, 65 and 62 µmol L–1, respectively. Polyoxins repressed the transcription of genes encoding proteins required for aflatoxin biosynthesis in A. parasiticus and fumonisin biosynthesis in F. fujikuroi. Polyoxin K and D also inhibited conidiation in A. parasiticus and F. fujikuroi, respectively. These results suggest that a mixture of polyoxins may effectively prevent co-contamination of aflatoxin and fumonisin in foods.
... were already described. The mechanisms are described mainly for aflatoxins where co-cultures as well as bacterial metabolites such as blasticidin and its derivatives, aflastatin A and dioctatin A, presented an anti-aflatoxinogenic effect by downregulating the expression of aflatoxin cluster genes [16,36,[39][40][41][42][43]. ...
Ochratoxin A (OTA) is a mycotoxin produced by several species of Aspergillus and Penicillium that contaminate food and feed raw materials. To reduce OTA contamination, we first tested in vitro, actinobacterial strains as potential biocontrol agents and afterward, through a physical decontamination method using activated carbon fibers (ACFs). Actinobacterial strains were screened for their ability to reduce OTA in solid co-culture with A. carbonarius, which is the major OTA-producing species in European vineyards. Four strains showed a high affinity for removing OTA (67%–83%) with no significant effect on fungal growth (<20%). The mechanism of action was first studied by analyzing the expression of OTA cluster genes (acOTApks, acOTAnrps, acOTAhal) by RT-qPCR showing a drastic reduction in all genes (7–15 times). Second, the ability of these strains to degrade OTA was assessed in vitro on ISP2 solid medium supplemented with OTA (100 µg/L). Two strains reduced OTA to undetectable levels. As for the physical method, high adsorption rates were obtained for ACFs at 0.8 g/L with a 50% adsorption of OTA in red wine by AC15 and 52% in grape juice by AC20 within 24 h. These promising methods could be complementarily applied toward reducing OTA contamination in food chains, which promotes food safety and quality.
A rich potential source of new antibiotics are undeveloped natural product cytotoxins, provided they can be derivatized to restrict their activity to bacteria. In this work, we describe modification of one such candidate, the broad-spectrum, translation termination inhibitor, blasticidin S. By semisynthetically modifying blasticidin S, we produced a series of ester derivatives of this highly polar, zwitterionic compound in a single step. These derivatives showed a marked increase in activity against Gram-positive bacteria and an increase in selectivity index for pathogenic bacteria over human cells. The results of this study suggest that semisynthetic derivatization of blasticidin S and other neglected natural product antimicrobials has the potential to increase their activity against and selectivity for bacteria, an approach that can be leveraged for the development of leads against antimicrobial resistant pathogens.
In this work the first H-bond-directed vinylogous iminium ion strategy has been developed as a convenient strategy for the γ,δ-functionalization of vinyl-substituted heteroaromatic aldehydes. Their reaction with α-mercaptoketones proceeds in a cascade manner involving 1,6-addition followed by intramolecular aldol reaction. Excellent stereoselectivities have been obtained as a result of the H-bond interactions controlling the outcome of the cyclization step. The application of the strategy for the synthesis of tricyclic compounds bearing furan, tetrahydrothiophene and dihydropyran moieties has also been demonstrated.
Non‐conventional yeast Candida famata and Ogataea polymorpha are interesting organisms for basic and applied studies. O. polymorpha is methylotrophic thermotolerant yeast capable of xylose alcoholic fermentation whereas C. famata is capable of riboflavin overproduction. Still the new tools for molecular research of these species are needed. The aim of this study was to develop the new dominant selective markers for C. famata and O. polymorpha usable in metabolic engineering experiments. In this work, the BSD gene from Aspergillus terreus coding for blasticidin S deaminase, O. polymorpha AUR1 gene required for sphingolipid synthesis and IMH3 gene, which encodes IMP dehydrogenase, were tested as the new dominant selective marker genes.
Our results showed that AUR1 and IMH3 genes could be used as dominant selective markers for O. polymorpha with frequencies of transformation of 40 and 20 transformants per μg of DNA, respectively. The IMH3 gene was successfully used as the marker for construction of O. polymorpha strains with increased ethanol production from xylose due to overexpression of TAL1, TKL1 and AOX1 genes. The BSD gene from A. terreus, conferring resistance to blasticidin, was found to be efficient for selection of C. famata transformants.
