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Toxins Nov 2020Carbon is one of the most important nutrients for the development and secondary metabolism in fungi. CreA is the major transcriptional factor mediating carbon catabolite...
Carbon is one of the most important nutrients for the development and secondary metabolism in fungi. CreA is the major transcriptional factor mediating carbon catabolite repression, which is employed in the utilization of carbon sources. contaminates various food and feed containing different carbon sources by producing ochratoxin A (OTA). However, little is known about the function of in regulating the morphology and OTA production of . To give an insight into the mechanism of the carbon sources regulating development of and OTA production, we have identified in . The homologous recombination strategy was used to generate the deletion mutant (Δ). We have investigated the morphology and OTA production of the wild type (WT) and Δ of with media containing different carbon sources (glucose, fructose, maltose, D-xylose, D-mannose, acetate, D-galactose, D-mannitol and lactose). Δ showed a significant growth and conidiation defect on all media as compared with WT. Glucose and maltose were the most inducing media for OTA production by , followed by sucrose and the nutrient-rich Yeast Extract Sucrose (YES) and Potato Dextrose Agar (PDA). The deletion of led to a drastic reduction of OTA production on all kinds of media except PDA, which was supported by the expression profile of OTA biosynthetic genes. Furthermore, infection studies of Δ on oats and pears showed the involvement of in the pathogenicity of . Thus, these results suggest that regulates morphological development and OTA biosynthesis in response to carbon sources in .
Topics: Aspergillus ochraceus; Catabolite Repression; Fungal Proteins; Gene Expression Regulation, Fungal; Mutation; Ochratoxins; Phylogeny; Repressor Proteins
PubMed: 33152993
DOI: 10.3390/toxins12110697 -
Asian Pacific Journal of Tropical... Oct 2011To isolate and characterize the bioactive secondary metabolites from Aspergillus ochraceus (A. ochraceus) MP2 fungi.
OBJECTIVE
To isolate and characterize the bioactive secondary metabolites from Aspergillus ochraceus (A. ochraceus) MP2 fungi.
METHODS
The anti bacterial activity of marine sponge derived fungi A. ochraceus MP2 was thoroughly investigated against antagonistic human pathogens. The optimum inhibitory concentration of the fungi in the elite solvent was also determined. The promising extracts that showed good antimicrobial activity were subjected to further analytical separation to get individual distinct metabolites and the eluants were further identified by GC MS instrumental analysis. The molecular characterization of the elite fungal strains were done by isolating their genomic DNA and amplify the internal transcribed spacer (ITS) region of 5.8s rRNA using specific ITS primer. The novelty of the strain was proved by homology search tools and elite sequences was submitted to GENBANK.
RESULTS
Three bioactive compounds were characterized to reveal their identity, chemical formula and structure. The first elutant was identified asα- Campholene aldehyde with chemical formula C10 H16 O and molecular weight 152 Da. The second elutant was identified as Lucenin-2 and chemical formula C27 H30 O16 and molecular weight 610 Da. The third elutant was identified as 6-Ethyloct- 3-yl- 2- ethylhexyl ester with Chemical formula C26 H42 O4 with molecular weight 418 Da.
CONCLUSIONS
The isolated compounds showed significant antimicrobial activity against potential human pathogens. Microbial secondary metabolites represent a large source of compounds endowed with ingenious structures and potent biological activities.
Topics: Animals; Anti-Bacterial Agents; Aspergillus ochraceus; Bacteria; Microbial Sensitivity Tests; Porifera
PubMed: 23569796
DOI: 10.1016/S2221-1691(11)60083-X -
Frontiers in Microbiology 2019is reported to be the major contributor of ochratoxin A (OTA), classified as one of the possible human carcinogen (group 2B) by the International Agency for Research on...
is reported to be the major contributor of ochratoxin A (OTA), classified as one of the possible human carcinogen (group 2B) by the International Agency for Research on Cancer. The heterotrimeric velvet complex proteins, LaeA/VeA/VelB, have been most studied in fungi to clarify the relation between light-dependent morphology and secondary metabolism. To explore possible genetic targets to control OTA contamination, we have identified laeA, veA, and velB in . The loss of , , and yielded mutants with differences in vegetative growth and conidial production. Especially, ΔlaeA almost lost the ability to generate conidiaphore under dark condition. The deletion of , , and drastically reduced the production of OTA. The wild-type produced about 1 and 7 μg/cm OTA under light and dark conditions on media, whereas the three gene deletion mutants produced less than 20 ng/cm OTA, which was correlated with a down regulation of OTA biosynthetic genes. Pathogenicity studies of ΔlaeA, ΔveA, and ΔvelB showed their reduction in disease severity in pears. Furthermore, 66.1% of the backbone genes in secondary metabolite gene cluster were significantly regulated, among which 81.6% were downregulated. Taking together, these results revealed that velvet complex proteins played crucial roles in asexual development, secondary metabolism, and fungal virulence in .
PubMed: 31849898
DOI: 10.3389/fmicb.2019.02759 -
Journal of Food Protection Jun 2001Ochratoxin A (OA) is receiving attention worldwide because of the hazard it poses to human and animal health. OA contamination of commodities, such as cereals or pork... (Review)
Review
Ochratoxin A (OA) is receiving attention worldwide because of the hazard it poses to human and animal health. OA contamination of commodities, such as cereals or pork and poultry meat, is well recognized. Nevertheless, there is an increasing number of articles reporting OA contamination in other food commodities, such as coffee, beer, wine, grape juice, and milk, in the last few years. This continuous and increasing exposure to OA that humans experience is reflected in the high incidence of OA in both human blood and milk in several countries. OA was believed to be produced only by Aspergillus ochraceus and closely related species of section Circumdati and by Penicillium verrucosum; however, in the genus Aspergillus, the production of OA has been recently reported by species outside the section Circumdati. Thus, it has been clearly established as a metabolite of different species of the section Nigri, such as Aspergillus niger and Aspergillus carbonarius. OA production ability by Aspergillus spp. is more widespread than previously thought; therefore, there is the possibility that unexpected species can be new sources of this mycotoxin in their natural substrates.
Topics: Animals; Aspergillus; Beer; Beverages; Carcinogens; Coffee; Food Contamination; Food Microbiology; Milk; Ochratoxins; Wine
PubMed: 11403149
DOI: 10.4315/0362-028x-64.6.903 -
Environmental Microbiology Jun 2019To date, no demonstration of a direct correlation between the presence of mycoviruses and the quantitative or qualitative modulation of mycotoxins has been shown. In our...
To date, no demonstration of a direct correlation between the presence of mycoviruses and the quantitative or qualitative modulation of mycotoxins has been shown. In our study, we transfected a virus-free ochratoxin A (OTA)-producing isolate of Aspergillus ochraceus with purified mycoviruses from a different A. ochraceus isolate and from Penicillium aurantiogriseum. Among the mycoviruses tested, only Aspergillus ochraceus virus (AoV), a partitivirus widespread in A. ochraceus, caused a specific interaction that led to an overproduction of OTA, which is regulated by the European Commission and is the second most important contaminant of food and feed commodities. Gene expression analysis failed to reveal a specific viral upregulation of the mRNA of genes considered to play a role in the OTA biosynthetic pathway. Furthermore, AoOTApks1, a polyketide synthase gene considered essential for OTA production, is surprisingly absent in the genome of our OTA-producing isolate. The possible biological and evolutionary implications of the mycoviral regulation of mycotoxin production are discussed.
Topics: Aspergillus ochraceus; Biosynthetic Pathways; Fungal Proteins; Fungal Viruses; Ochratoxins; Penicillium; Polyketide Synthases
PubMed: 30289193
DOI: 10.1111/1462-2920.14436 -
Occurrence of fungi and mycotoxins in herbal medicines and rapid detection of toxin-producing fungi.Environmental Pollution (Barking, Essex... Sep 2023Contamination from external hazardous materials may greatly influence the safety and efficacy of herbal medicines. This paper aimed to evaluate the levels of...
Contamination from external hazardous materials may greatly influence the safety and efficacy of herbal medicines. This paper aimed to evaluate the levels of contamination by mycotoxins and toxigenic fungi in herbal medicines and establish a rapid method for detecting toxin-producing fungi. Herein, 62.92%, 36.25%, and 64.17% of herbal medicines were contaminated by aflatoxins (AFs), ochratoxins, and fumonisins, respectively. Aspergillus (43.77%), Fusarium (5.17%), and Cladosporium (4.46%) were the three predominant genera. Spearman's correlation results showed that Aspergillus and Fusarium were significantly and positively correlated with mycotoxin content (R > 0.5, P < 0.05). In addition, 323 fungal strains were isolated from herbal medicines, and 20 species were identified, mainly belonging to Aspergillus and Penicillium. Analysis of potential mycotoxin-producing fungi showed that Aspergillus flavus can produce AFs, and Aspergillus ochraceus and Aspergillus niger can produce ochratoxin A (OTA). Multiplex real-time polymerase chain reaction showed that A. flavus harbored AF synthesis genes (aflR), and A. ochraceus and A. niger harbored OTA synthesis genes (aoksl). With these synthesis genes, 67.07% and 37.20% of 164 herbal medicines were positive for toxigenic genes. Furthermore, an excellent correlation was found between the above gene copies and mycotoxin content (R = 0.99). Our results confirmed the high detection rate of mycotoxins in herbal medicines and identified pivotal AF- and OTA-producing fungi. In conclusion, this paper provided the contamination status of fungi and mycotoxins in herbal medicines and established a rapid method for detecting toxigenic fungi.
Topics: Mycotoxins; Fungi; Aflatoxins; Fumonisins; Plant Extracts; Food Contamination
PubMed: 37343918
DOI: 10.1016/j.envpol.2023.122082 -
Applied and Environmental Microbiology Oct 2018Ochratoxin A (OTA) is a toxic secondary metabolite produced by and species that widely contaminates food and feed. We sequenced and assembled the complete ∼37-Mb...
Ochratoxin A (OTA) is a toxic secondary metabolite produced by and species that widely contaminates food and feed. We sequenced and assembled the complete ∼37-Mb genome of fc-1, a well-known producer of OTA. Key genes of the OTA biosynthetic pathway were identified by comparative genomic analyses with five other sequenced OTA-producing fungi: , , , , and OTA production was completely inhibited in the deletion mutants (Δ, Δ, Δ, Δ, and Δ), and OTA biosynthesis was restored by feeding a postblock substrate to the corresponding mutant. The OTA biosynthetic pathway was unblocked in the Δ mutant by the addition of heterologously expressed halogenase. OTA biosynthesis begins with a polyketide synthase (PKS), OtaA, utilizing acetyl coenzyme A (acetyl-CoA) and malonyl-CoA to synthesize 7-methylmellein, which is oxidized to OTβ by cytochrome P450 monooxygenase (OtaC). OTβ and l-β-phenylalanine are combined by a nonribosomal peptide synthetase (NRPS), OtaB, to form an amide bond to synthesize OTB. Finally, OTB is chlorinated by a halogenase (OtaD) to OTA. The genes were expressed at low levels in the Δ mutant. A second regulator, , which is adjacent to the biosynthetic gene, could modulate only the expression of , , and Thus, we have identified a consensus OTA biosynthetic pathway that can be used to prevent and control OTA synthesis and will help us understand the variation and production of the intermediate components in the biosynthetic pathway. Ochratoxin A (OTA) is a significant mycotoxin that contaminates cereal products, coffee, grapes, wine, cheese, and meat. OTA is nephrotoxic, carcinogenic, teratogenic, and immunotoxic. OTA contamination is a serious threat to food safety, endangers human health, and can cause huge economic losses. At present, >20 species of the genera and are known to produce OTA. Here we demonstrate that a consensus OTA biosynthetic pathway exists in all OTA-producing fungi and is encoded by a gene cluster containing four highly conserved biosynthetic genes and a bZIP transcription factor.
Topics: Aspergillus ochraceus; Biosynthetic Pathways; Comparative Genomic Hybridization; Cytochrome P-450 Enzyme System; Fungal Proteins; Genome, Fungal; Genomics; Multigene Family; Ochratoxins; Penicillium; Peptide Synthases; Polyketide Synthases
PubMed: 30054361
DOI: 10.1128/AEM.01009-18 -
Critical Reviews in Food Science and... 2015Ochratoxin A (OTA) is a mycotoxin produced by several fungal species including Aspergillus ochraceus, A. carbonarius, A. niger, and Penicillium verrucosum. OTA causes... (Review)
Review
Ochratoxin A (OTA) is a mycotoxin produced by several fungal species including Aspergillus ochraceus, A. carbonarius, A. niger, and Penicillium verrucosum. OTA causes nephrotoxicity and renal tumors in a variety of animal species; however, human health effects are less well-characterized. Various studies have linked OTA exposure with the human diseases Balkan endemic nephropathy (BEN) and chronic interstitial nephropathy (CIN), as well as other renal diseases. This study reviews the epidemiological literature on OTA exposure and adverse health effects in different populations worldwide, and assesses the potential human health risks of OTA exposure. Epidemiological studies identified in a systematic review were used to calculate unadjusted odds ratios for OTA associated with various health endpoints. With one exception, there appears to be no statistically significant evidence for human health risks associated with OTA exposure. One Egyptian study showed a significantly higher risk of nephritic syndrome in those with very high urinary OTA levels compared with relatively unexposed individuals; however, other potential risk factors were not controlled for in the study. Larger cohort or case-control studies are needed in the future to better establish potential OTA-related human health effects, and further duplicate-diet studies are needed to validate biomarkers of OTA exposure in humans.
Topics: Balkan Nephropathy; Evidence-Based Medicine; Food Contamination; Food Microbiology; Humans; Nephrotic Syndrome; Ochratoxins; Risk Assessment
PubMed: 24874522
DOI: 10.1080/10408398.2012.724480 -
Molecules (Basel, Switzerland) Aug 2018The grain contamination by spp. has been a serious issue. This study exhibited the excellent antifungal effects of the essential oil compounds (EOCs) geraniol and...
The grain contamination by spp. has been a serious issue. This study exhibited the excellent antifungal effects of the essential oil compounds (EOCs) geraniol and citral against common grain pathogens ( and ) in vitro and in situ. The inhibitory mechanisms were also evaluated from the perspective of cell membrane permeability, reactive oxygen species (ROS) generation, and spp. growth-related gene expression. Meanwhile, the combined effects of EOCs in the vapor phase and modified atmosphere packaging (MAP) were examined to find an alternative preservation method for controlling spp. The results indicated that citral exhibited the antifungal activity mainly by downregulating the sporulation- and growth-related genes for both pathogens. Geraniol displayed inhibitory effectiveness against predominantly by inducing the intracellular ROS accumulation and showed toxicity against principally by changing cell membrane permeability. Furthermore, the synthetic effects of EOCs and MAP (75% CO₂ and 25% N₂) induced better grain quality than the current commercial fumigant AlP. These findings reveal that EOCs have potential to be a novel grain preservative for further application.
Topics: Acyclic Monoterpenes; Antifungal Agents; Aspergillus flavus; Aspergillus ochraceus; Cell Membrane Permeability; Edible Grain; Gene Expression Profiling; Microbial Sensitivity Tests; Monoterpenes; Oils, Volatile; Reactive Oxygen Species; Terpenes
PubMed: 30131466
DOI: 10.3390/molecules23092108 -
Frontiers in Fungal Biology 2022fungi produce mycotoxins that are detrimental to human and animal health. Two sections of aspergilli are of particular importance to cereal food crops such as corn and...
fungi produce mycotoxins that are detrimental to human and animal health. Two sections of aspergilli are of particular importance to cereal food crops such as corn and barley. section species like and produce aflatoxins, while section species like and produce ochratoxin A. Mitigating these toxins in food and feed is a critical and ongoing worldwide effort. We have previously investigated biosynthetic gene clusters in that are linked to fungal virulence in corn. We found that one such cluster, , is responsible for the production of aspergillic acid, an iron-binding, hydroxamic acid-containing pyrazinone metabolite. Furthermore, we found that the gene cluster is present in many other aflatoxin- and ochratoxin-producing aspergilli. The core gene in the cluster encodes the small nonribosomal peptide synthetase-like (NRPS-like) protein AsaC. We have swapped the ortholog from into , replacing its native copy, and have also cloned both orthologs into . We show that AsaC orthologs in section and section , while only containing adenylation-thiolation-reductase (ATR) domains, can selectively biosynthesize distinct pyrazinone natural products: deoxyaspergillic acid and flavacol, respectively. Because pyrazinone natural products and the gene clusters responsible for their production are implicated in a variety of important microbe-host interactions, uncovering the function and selectivity of the enzymes involved could lead to strategies that ultimately benefit human health.
PubMed: 37746228
DOI: 10.3389/ffunb.2022.1029195