Search

The occurrence of mycotoxins on grapes poses a high risk for food safety, thus, it is necessary to implement effective prevention methods. In this work, a metagenomic approach revealed the presence of important mycotoxigenic fungi in grape berries, including Aspergillus flavus, Aspergillus niger aggregate species, or Aspergillus section Circumdati. However, A. carbonarius was not detected in any sample. One of the samples was not contaminated by any mycotoxigenic species, and, therefore, it was selected for the isolation of potential biocontrol agents. In this context, Hanseniaspora uvarum U1 was selected for biocontrol in vitro assays. The results showed that this yeast is able to reduce the growth rate of the main ochratoxigenic and aflatoxigenic Aspergillus spp. occurring on grapes. Moreover, H. uvarum U1 seems to be an effective detoxifying agent for aflatoxin B1 and ochratoxin A, probably mediated by the mechanisms of adsorption to the cell wall and other active mechanisms. Therefore, H. uvarum U1 should be considered in an integrated approach to preventing AFB1 and OTA in grapes due to its potential as a biocontrol and detoxifying agent.

Aspergillus section Circumdati includes 27 species, some of which are considered ochratoxin A (OTA) producers. However, there is considerable controversy about their potential OTA synthesis ability. In this work, the complete genomes of 13 species of Aspergillus section Circumdati were analyzed in order to study the cluster of OTA biosynthetic genes and the region was compared to those previously reported in A. steynii and A. westerdijkiae. The results obtained reveal that the genomes of some species in this section, including A. affinis, A. cretensis, A. elegans, A. muricatus, A. pulvericola, A. roseoglobulosus, and A. subramanianii, contain a potentially functional OTA biosynthetic cluster. Therefore, they might be able to synthesize the toxin. On the contrary, A. melleus, A. ochraceus, A. ostianus, A. persii, A. sclerotiorum, A. sesamicola, and A. westlandensis contain a truncated version of the cluster that lacks many of the genes involved in OTA biosynthesis, which might be related to their inability to produce OTA. The gain/loss pattern is different in all species, which suggests that the genetic evolution of this region might be due to independent events.

Aspergillus section Circumdati includes 27 species, some of which are considered ochratoxin A (OTA) producers. However, there is considerable controversy about their potential OTA synthesis ability. In this work, the complete genomes of 13 species of Aspergillus section Circumdati were analyzed in order to study the cluster of OTA biosynthetic genes and the region was compared to those previously reported in A. steynii and A. westerdijkiae. The results obtained reveal that the genomes of some species in this section, including A. affinis, A. cretensis, A. elegans, A. muricatus, A. pulvericola, A. roseoglobulosus, and A. subramanianii, contain a potentially functional OTA biosynthetic cluster. Therefore, they might be able to synthesize the toxin. On the contrary, A. melleus, A. ochraceus, A. ostianus, A. persii, A. sclerotiorum, A. sesamicola, and A. westlandensis contain a truncated version of the cluster that lacks many of the genes involved in OTA biosynthesis, which might be related to their inability to produce OTA. The gain/loss pattern is different in all species, which suggests that the genetic evolution of this region might be due to independent events.

Ochratoxin A (OTA) is one of the most important mycotoxins due to its toxic properties and worldwide distribution which is produced by several Aspergillus and Penicillium species. The knowledge of OTA biosynthetic genes and understanding of the mechanisms involved in their regulation are essential. In this work, we obtained a clear picture of biosynthetic genes organization in the main OTA-producing Aspergillus and Penicillium species (A. steynii, A. westerdijkiae, A. niger, A. carbonarius and P. nordicum) using complete genome sequences obtained in this work or previously available on databases. The results revealed a region containing five ORFs which predicted five proteins: halogenase, bZIP transcription factor, cytochrome P450 monooxygenase, non-ribosomal peptide synthetase and polyketide synthase in all the five species. Genetic synteny was conserved in both Penicillium and Aspergillus species although genomic location seemed to be different since the clusters presented different flanking regions (except for A. steynii and A. westerdijkiae); these observations support the hypothesis of the orthology of this genomic region and that it might have been acquired by horizontal transfer. New real-time RT-PCR assays for quantification of the expression of these OTA biosynthetic genes were developed. In all species, the five genes were consistently expressed in OTA-producing strains in permissive conditions. These protocols might favour futures studies on the regulation of biosynthetic genes in order to develop new efficient control methods to avoid OTA entering the food chain.

Mycotoxin contamination is one of the main problems affecting corn production, due to its significant risk to human and animal health. The Fusarium and Aspergillus species are the main producers of mycotoxins in maize, infecting both pre-harvest and during storage. In this work, we evaluated the presence of mycotoxins and their producing species along maize production cycles in three different stages (anthesis, harvest, and storage) during three consecutive seasons (2016&ndash, 2018). Fungal occurrences were studied using species-specific PCR protocols, whereas mycotoxin levels were determined by LC-MS/MS. Fumonisin-producing Fusarium species (F. verticillioides and F. proliferatum), as well as the aflatoxin producer Aspergillus flavus, were the most predominant species at all stages, although, during some seasons, the presence of F. graminearum and A. niger aggregate species were also identified. Contrastingly, fumonisins were the only mycotoxins detected and levels were always under legal regulations. The results presented here demonstrate that even when fungal contamination occurs at the early stages of the maize production cycle, the application of good agricultural and storage practices might be crucial to ensure mycotoxin-free grains.

The Aspergillus niger aggregate contains 15 morphologically indistinguishable species which presence is related to ochratoxin A (OTA) and fumonisin B2 (FB2) contamination of foodstuffs. The taxonomy of this group was recently reevaluated and there is a need of new studies regarding the risk that these species might pose to food security. 258 isolates of A. niger aggregate obtained from a variety of products from Spain were classified by molecular methods being A. tubingensis the most frequently occurring (67.5%) followed by A. welwitschiae (19.4%) and A. niger (11.7%). Their potential ability to produce mycotoxins was evaluated by PCR protocols which allow a rapid detection of OTA and FB2 biosynthetic genes in their genomes. OTA production is not widespread in A. niger aggregate since only 17% of A. niger and 6% of A. welwitschiae isolates presented the complete biosynthetic cluster whereas the lack of the cluster was confirmed in all A. tubingensis isolates. On the other hand, A. niger and A. welwitschiae seem to be important FB2 producers with 97% and 29% of the isolates, respectively, presenting the complete cluster. The genes involved in OTA and FB2 were overexpressed in producing isolates and their expression was related to mycotoxin synthesis.

Aspergillus steynii is probably the most relevant species of section Circumdati producing ochratoxin A (OTA). This mycotoxin contaminates a wide number of commodities and it is highly toxic for humans and animals. Little is known on the biosynthetic genes and their regulation in Aspergillus species. In this work, we identified and analysed three contiguous genes in A. steynii using 5'-RACE and genome walking approaches which predicted a cytochrome P450 monooxygenase (p450ste), a non-ribosomal peptide synthetase (nrpsste) and a polyketide synthase (pksste). These three genes were contiguous within a 20742 bp long genomic DNA fragment. Their corresponding cDNA were sequenced and their expression was analysed in three A. steynii strains using real time RT-PCR specific assays in permissive conditions in in vitro cultures. OTA was also analysed in these cultures. Comparative analyses of predicted genomic, cDNA and amino acid sequences were performed with sequences of similar gene functions. All the results obtained in these analyses were consistent and point out the involvement of these three genes in OTA biosynthesis by A. steynii and showed a co-ordinated expression pattern. This is the first time that a clustered organization OTA biosynthetic genes has been reported in Aspergillus genus. The results also suggested that this situation might be common in Aspergillus OTA-producing species and distinct to the one described for Penicillium species.

The determination of aflatoxin production ability and differentiation of aflatoxigenic strains can be assessed by monitoring the expression of one or several key genes using reverse transcription polymerase chain reaction (RT-PCR). We herein describe the methods for RNA induction, extraction, and quality determination, and the RT-PCR conditions used to evaluate the ability of a given Aspergillus strain to produce aflatoxins. info:eu-repo/semantics/publishedVersion

Contamination of barley by moulds and mycotoxins results in quality and nutritional losses and represents a significant hazard to the food chain. The presence of aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2) and ochratoxin A (OTA) in stored barley in Spain has been studied. Species-specific PCR assays were used for detection of Aspergillus flavus, A. parasiticus, A. ochraceus, A. steynii, A. westerdijkiae, A. carbonarius and A. niger aggregate in mycotoxin-positive barley samples at different incubation times (0, 1 and 2 days). Classical enumeration techniques (CFU/g) in different culture media for evaluation of Aspergillus in sections Flavi, Circumdati and Nigri were also used. One hundred and five barley kernel samples were collected in Spanish grain stores from 2008 to 2010, and analyzed using a previously optimized method involving accelerated solvent extraction, cleanup by immunoaffinity column, liquid chromatographic separation, post-column derivatization with iodine and fluorescence detection. Twenty-nine samples were contaminated with at least one of the studied mycotoxins. AFB1, AFB2, AFG1, AFG2, and OTA were detected in 12.4%, 2.9%, 4.8%, 2.9%, and 20% of the samples, respectively. Aflatoxins and OTA co-occurred in 4.8% of the samples. Maximum mycotoxin levels (ng/g) were 0.61 (AFB1), 0.06 (AFB2), 0.26 (AFG1), 0.05 (AFG2), and 2.0 (OTA). The results of PCR assays indicated the presence of all the studied species, except A. westerdijkiae. The PCR assays showed high levels of natural contamination of barley with the studied species of Aspergillus which do not correspond to the expected number of CFU/g in the cultures. These results suggest that a high number of non-viable spores or hyphae may exist in the samples. This is the first study carried out on the levels of aflatoxins and OTA in barley grain in Spain. Likewise, this is the first report on the presence of aflatoxigenic and ochratoxigenic Aspergillus spp. in barley grain naturally contaminated with those mycotoxins using a species-specific PCR approach.

The objective of this study was to gain information about the toxigenic Aspergillus species present in a wide survey of retail samples of paprika and chilli collected in Spain. Detection of these mycotoxigenic species was performed with an optimized protocol for paprika and chilli which includes a set of species-specific PCR assays. Occurrence of toxigenic Aspergillus species was higher in paprika than in chilli samples (83.9% and 64.5%, respectively). Paprika showed also the highest percentage of co-occurrence of two or more different species (43.6%) in comparison with chilli (35.5%). The most common aspergilli were Aspergillus niger aggregate (67.7%), followed by Aspergillus flavus (49.5%). Aspergillus carbonarius, Aspergillus parasiticus and Aspergillus steynii were detected at lower frequency (1.1%). The high co-occurrence of Aspergillus species able to produce ochratoxin A and aflatoxins, particularly in paprika, suggested the need of a more efficient control during processing and storage to reduce fungal contamination, and additional legislation to consider the simultaneous presence of both toxins in these matrices.

Aflatoxins are important mycotoxins that represent a serious risk for human and animal health. These mycotoxins are mainly produced by Aspergillus flavus and Aspergillus parasiticus, two closely related species with different array of aflatoxins. In this work, two specific quantitative PCR (qPCR) assays were developed to detect and quantify both species in wheat flour using primers based on the multicopy ITS2 rDNA target sequence. The species specificity of the assays was tested in a wide range of strains of these species and others colonizing the same commodities. The sensitivity of the assay was estimated in 2.5 pg/reaction in both species. Discrimination capacity for detection and relative quantification of A. flavus and A. parasiticus DNA were analyzed using samples with DNA mixtures containing also other fungal species at different ratios. Both qPCR assays could detect spore concentrations equal or higher than 10(6)spores/g in flour samples without prior incubation. These assays are valuable tools to improve diagnosis at an early stage and in all critical control points of food chain integrated in HACCP strategies.

International audience; Aspergillus parasiticus is considered one of the most important aflatoxin producing species which contaminates foodstuffs and beverages for human consumption. In this work, a specific and highly sensitive PCR protocol was developed to detect A. parasiticus using primers designed on the multicopy internal transcribed region of the rDNA unit (ITS1-5.8S-ITS2 rDNA). The assay proved to be highly specific to A. parasiticus when it was tested in a wide sample of related species and other fungal species commonly found in commodities, and it allowed discrimination from the closely related A. flavus. Accuracy of detection and quantification by conventional PCR were tested with genomic DNA obtained from wheat flour artificially contaminated with spore suspensions of known concentrations. Spore concentrations equal or higher than 106 spore/g could be detected by the assay directly without prior incubation of the samples. The assay described might be incorporated in routine analyses at critical points of the food chain within HAAPC strategies.

Agroproducts contaminated by ochratoxin A (OTA) represent a risk for human and animal health and, therefore, maximum limits have been established by Food Safety Authorities. Reduction of OTA contamination may be accomplished by early detection of OTA-producing fungal species using rapid, specific and sensitive detection and quantification by PCR-based methods. Aspergillus carbonarius is one of the most important OTA-producing species, in particular in grapes and derivatives from Mediterranean regions. In this work, highly efficient quantitative PCR assays using SYBR Green I and TaqMan methods were developed for specific detection of A. carbonarius to be used in grapes. The primers and the TaqMan probe were based on the internal transcribed region 2 multicopy region (internal 2 sequence of the rRNA gene). The specificity and sensitivity of both assays were tested on genomic DNA mixtures of several A. carbonarius strains and other fungal species frequently present in grapes. Both methods were also compared using grapes inoculated with different spore concentrations of A. carbonarius, detecting up to 0.4 pg DNA g(-1) grape berries. The efficiency and sensitivity of both methods were comparable and only the lower cost of SYBR Green might favour its use in routine screenings.

Aspergillus ochraceus and A. westerdijkiae are considered the most important Ochratoxin A (OTA) producing species included in Aspergillus section Circumdati which contaminate foodstuffs and beverages for human consumption. In this work a real-time quantitative PCR protocol was developed to detect both species using SYBR Green and primers designed on the basis of the multicopy ITS1 region of the rDNA. The assay had high efficiency (94%) and showed no inhibition by host or fungal DNA other than the target species. The lower detection limit of the target DNA was 2.5 pg/reaction. Accuracy of detection and quantification by qPCR were tested with genomic DNA obtained from green coffee beans and grapes artificially contaminated with spore suspensions of known concentrations. Spore concentrations equal or higher than 10(6) spore/ml could be detected by the assay directly without prior incubation of the samples and a positive relationship was observed between incubation time and qPCR values. The assay developed would allow rapid, specific, accurate and sensitive detection and quantification of A. ochraceus and A. westerdijkiae to be directly used in a critical point of the food chain, before harvesting green coffee and grape berries, to predict and control fungal growth and OTA production.

Ochratoxin A (OTA) is a highly toxigenic mycotoxin commonly present in a number of diverse agroproducts. Aspergillus Section Circumdati includes some of the most important OTA-producing species: Aspergillus ochraceus, Aspergillus elegans and the recently described Aspergillus steynii and Aspergillus westerdijkiae. In this work, OTA production by several strains of these four species from diverse origins and food matrices was examined. Identification of all the strains was carried out by specific PCR assays. The strains were cultivated in CYA solid medium and OTA was measured by HLPC. This study demonstrated for the first time the high capacity of A. steynii strains to produce OTA at higher levels than A. westerdijkiae,A. ochraceus and A. elegans strains showed low levels or no production at all. In conclusion, the results of this study suggest that the occurrence of A. steynii and A. westerdijkiae might represent the major potential risk for OTA contamination due to their high production and the diversity of commodities that these species may contaminate.

BACKGROUND Fourteen vineyards from two different agro-climatic regions in Spain were sampled in two consecutive years in order to determinate the grape mycobiota and diversity indexes with the final aim to define the potential mycotoxigenic species from both regions and their relationship. RESULTS The most common fungal genera encountered were Aspergillus (30.0%), Alternaria (53.2%), Cladosporium (11.9%) and Penicillium (2.9%). Black aspergilli presence in the hotter region (south) was significantly higher (P < 0.05) than in the northeast in both years. Among black aspergilli, A. tubingensis seemed to be the better adapted species to environmental conditions, while A. carbonarius was the main potentially ochratoxigenic species in both regions and years, owing to the most relevant percentage of ochratoxigenic isolates. Ochratoxin A (OTA)-positive musts were only detected from southern vineyards, although contamination was always lower than 0.1 µg L−1. Finally, none of black aspergilli tested produced fumonisins (FBs) on Czapek yeast extract agar (CYA), while 63% of A. niger tested produced FB2 when inoculated on CYA20S, reaching 100% of isolates from the south. CONCLUSION Climate change scenarios in southern Europe point to an increase in temperature and drought. This could promote particularly adapted species such as A. niger, decreasing OTA risk, but this could lead to an increase in FB2 presence. © 2014 Society of Chemical Industry

Aspergillus steynii and Aspergillus westerdijkiae are the main ochratoxin A (OTA) producing species of Aspergillus section Circumdati. Due to its recent description, few data are available about the influence of cophysiological factors on their growth and OTA production profiles. In this work, the effect of temperature (20, 24 and 28ºC) and water activity (aw) (0.928, 0.964 and 0.995) on rowth, sporulation and OTA production by these fungi was examined in CYA and media prepared from paprika, green coffee, anise, grapes, maize and barley. Growth was positively affected by the highest temperature and aw values indicating that both species might be expected in warm climates or storage conditions. However, optimal growth conditions showed differences depending on the medium. OTA production was markedly affected by substrate and showed qualitative and quantitative differences. Both species, especially A. steynii, represent a great potential risk of OTA contamination due to their high production in a variety of conditions and substrates, in particular in barley and paprika-based media. Additionally, neither growth nor sporulation did result good indicators of OTA production by A. steynii or A. westerdijkiae;therefore, specific and highly-sensitive detection methods become essential tools for control strategies to reduce OTA risk by these species.

Aspergillus westerdijkiae is one of the most relevant ochratoxin A (OTA) producing species within the Section Circumdati contaminating a number of agroproducts. The yeast Debaryomyces hansenii CYC 1244 was previously reported to be able to reduce growth and extracellular OTA produced by A. westerdijkiae. In this work, we examined several mechanisms possibly involved in this OTA reduction in in vitro experiments. OTA biosynthesis was evaluated by quantitation of expression levels of pks (polyketide synthase) and p450-B03 (cytochrome p450 monooxygenase) genes using newly developed and specific real time RT-PCR protocols. Both genes showed significant lower levels in presence of D. hansenii CYC 1244 suggesting an effect on regulation of OTA biosynthesis at transcriptional level. High levels of removal of extracellular OTA were observed by adsorption to yeast cell walls, particularly at low pH (98% at pH 3). On the contrary, no evidences were obtained of absorption of OTA into yeast cells or the production of constitutively expressed enzymes that degrade OTA by D. hansenii CYC 1244. These results described the potential of this yeast strain as a safe and efficient biocontrol agent to decrease OTA in A. westerdijkiae and two important mechanisms involved which may permit its application at different points of the food chain.

Ochratoxin A (OTA) is one of the most important mycotoxins because of its high toxicity to both humans and animals and its occurrence in a number of basic foods and agro-products. Some of the main OTA-producing species belong to Aspergillus section Circumdati, whose taxonomy has been lately revised with the description of new species. The high morphological similarity of these species (Aspergillus ochraceus, Aspergillus steynii and Aspergillus westerdijkiae) makes difficult discrimination among them and with respect to the other species included in the same section unable to produce OTA. In this work, PCR assays specific for the OTA-producing species, A. ochraceus, A. steynii and A. westerdijkiae, were developed on the basis of the multicopy ITS regions of the rDNA. The assays were tested in a wide sample of isolates from diverse origins and culture collections, confirming their specificity, and revealing that the current identification of strains from section Circumdati might need a revision.