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Cebrián E, Roncero E, Delgado J, Núñez F, Rodríguez M. Deciphering Staphylococcus xylosus and Staphylococcus equorum mode of action against Penicillium nordicum in a dry-cured ham model system. Int J Food Microbiol 2023; 405:110342. [PMID: 37523903 DOI: 10.1016/j.ijfoodmicro.2023.110342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 06/09/2023] [Accepted: 07/25/2023] [Indexed: 08/02/2023]
Abstract
Penicillium nordicum is one of the major producers of ochratoxin A (OTA) in dry-cured ham. Staphylococcus xylosus Sx8 and Staphylococcus equorum Se31 have been previously proposed as biocontrol agents (BCAs) to prevent the OTA contamination, although their antifungal mode of action has not been established yet. Thus, the aim of this work was to elucidate their mode of action against P. nordicum in a dry-cured ham model system. For this, the effect of live cells, dead cells, and cell-free broth; the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays, antifungal effect of volatile compounds, OTA detoxification, and effect on fungal proteome were determined. No fungal growth was observed after 14 days of co-culture with live cells of each staphylococcus at 15 or 20 °C. However, such inhibition was not observed with either dead cells or extracellular extracts. The number of carbon sources utilised by P. nordicum was higher than those used by both cocci at 20 °C, whilst the opposite occurred at 15 °C. According to NOI, nutritional dominance depends on temperature, at 20 °C P. nordicum dominated the niche, but at 15 °C the mould is dominated by the BCAs. The volatile pattern generated by each coccus did not show antifungal effect, and both staphylococci failed to degrade or adsorb OTA. However, in the interaction assay, S. xylosus and S. equorum were able to decrease the fungal growth and its OTA production. In addition, proteomic analyses showed changes in the abundance of proteins related to the cell wall integrity (CWI), carbohydrate metabolism and the biosynthesis of secondary metabolites such as OTA. In conclusion, overall, the antagonistic effects of the two studied cocci against P. nordicum are greater at 15 °C than at 20 °C, being linked to competition for space and nutrients, triggering alterations in CWI pathway, OTA biosynthesis, and carbohydrate metabolism.
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Affiliation(s)
- Eva Cebrián
- Higiene y Seguridad Alimentaria, Instituto de Investigación de Carne y Productos Cárnicos (IProCar), Facultad de Veterinaria, Universidad de Extremadura, Avda. de las Ciencias s/n, 10003 Cáceres, Spain
| | - Elia Roncero
- Higiene y Seguridad Alimentaria, Instituto de Investigación de Carne y Productos Cárnicos (IProCar), Facultad de Veterinaria, Universidad de Extremadura, Avda. de las Ciencias s/n, 10003 Cáceres, Spain
| | - Josué Delgado
- Higiene y Seguridad Alimentaria, Instituto de Investigación de Carne y Productos Cárnicos (IProCar), Facultad de Veterinaria, Universidad de Extremadura, Avda. de las Ciencias s/n, 10003 Cáceres, Spain.
| | - Félix Núñez
- Higiene y Seguridad Alimentaria, Instituto de Investigación de Carne y Productos Cárnicos (IProCar), Facultad de Veterinaria, Universidad de Extremadura, Avda. de las Ciencias s/n, 10003 Cáceres, Spain
| | - Mar Rodríguez
- Higiene y Seguridad Alimentaria, Instituto de Investigación de Carne y Productos Cárnicos (IProCar), Facultad de Veterinaria, Universidad de Extremadura, Avda. de las Ciencias s/n, 10003 Cáceres, Spain
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Yang P, Xiao W, Lu S, Jiang S, Jiang S, Chen J, Wu W, Zheng Z, Jiang S. Characterization of a Trametes versicolor aflatoxin B1-degrading enzyme (TV-AFB1D) and its application in the AFB1 degradation of contaminated rice in situ. Front Microbiol 2022; 13:960882. [PMID: 36187979 PMCID: PMC9515612 DOI: 10.3389/fmicb.2022.960882] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 08/24/2022] [Indexed: 11/13/2022] Open
Abstract
Aflatoxin B1 (AFB1) contaminates rice during harvest or storage and causes a considerable risk to human and animal health. In this study, Trametes versicolor AFB1-degrading enzyme (TV-AFB1D) gene recombinantly expressed in engineered E. coli BL21 (DE3) and Saccharomyces cerevisiae. The TV-AFB1D enzymatic characteristics and AFB1 degradation efficiency in contaminated rice were investigated. Results showed that the size of recombinant TV-AFB1D expressing in E. coli BL21 (DE3) and S. cerevisiae was appropriately 77 KDa. The kinetic equation of TV-AFB1D was y = 0.01671x + 1.80756 (R 2 = 0.994, Km = 9.24 mM, and Vmax = 553.23 mM/min). The Kcat and Kcat/Km values of TV-AFB1D were 0.07392 (s-1) and 8 M-1 s-1, respectively. The AFB1 concentration of contaminated rice decreased from 100 μg/ml to 32.6 μg/ml after treatment at 32°C for 5 h under the catabolism of TV-AFB1D. S. cerevisiae engineered strains carrying aldehyde oxidase 1 (AOX1) and Cauliflower mosaic virus 35 S (CaMV 35 S) promoters caused the residual AFB1 contents, respectively, decreased to 3.4 and 2.9 μg/g from the initial AFB1 content of 7.4 μg/g after 24 h of fermentation using AFB1-contaminated rice as substrate. The AFB1 degradation rates of S. cerevisiae engineered strains carrying AOX1 and CaMV promoters were 54 and 61%, respectively. Engineered S. cerevisiae strains integrated with TV-AFB1D expression cassettes were developed to simultaneously degrade AFB1 and produce ethanol using AFB1-contaminated rice as substrate. Thus, TV-AFB1D has significant application potential in the AFB1 decomposition from contaminated agricultural products.
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Affiliation(s)
- Peizhou Yang
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
| | - Wei Xiao
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
| | - Shuhua Lu
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
| | - Shuying Jiang
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
| | - Suwei Jiang
- Department of Biological, Food and Environment Engineering, Hefei University, Hefei, China
| | - Jianchao Chen
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
| | - Wenjing Wu
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
| | - Zhi Zheng
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
| | - Shaotong Jiang
- College of Food and Biological Engineering, Anhui Key Laboratory of Intensive Processing of Agriculture Products, Hefei University of Technology, Hefei, China
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Natarajan S, Balachandar D, Senthil N, Paranidharan V. Interaction of water activity and temperature on growth, gene expression, and aflatoxin B 1 production in Aspergillus flavus on Indian senna (Cassia angustifolia Vahl.). Int J Food Microbiol 2022; 361:109457. [PMID: 34742145 DOI: 10.1016/j.ijfoodmicro.2021.109457] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 10/09/2021] [Accepted: 10/22/2021] [Indexed: 11/19/2022]
Abstract
Senna (Cassia angustifolia Vahl.) is a medicinal crop with laxative properties, and it has significant demand in the global pharmaceutical market. Senna pods are highly susceptible to aflatoxin contamination, and the successful export of pods is hindered due to the regulatory limits of importing countries. The senna pod water activity (aw) from harvest to storage is the key factor determining AFB1 accumulation. The temperature conditions from field to warehouse also interact with pod aw, which influences fungal growth and AFB1 production. The determination of an ideal combination of aw and temperature led to the assessment of the critical control point for AFB1 synthesis in senna. Hence, this study aimed to evaluate the influence of aw (0.99, 0.96, 0.93, 0.90, and 0.87 aw) and temperature (20, 28, and 37 °C) on fungal growth, gene expression (aflR and aflS), and AFB1 production by A. flavus in senna agar medium. The fungus showed the longest lag time (7.7 days) at 20 °C with 0.87 aw. We observed that 0.96 aw (P < 0.01) was optimum for the diametric growth rate at 28 and 37 °C. However, the peak expression of regulatory genes (aflR and aflS) and the maximum AFB1 production were observed only at 28 °C (0.96 aw). The highest growth rate occurred at 37 °C, which did not favor the expression of genes and AFB1 production. However, at 28 °C, it positively correlated with gene expression and AFB1 production. The suppressed expression of regulatory genes and a trace amount of aflatoxin B1 were found at 20 °C with all the tested aw. In our experiments, the low aw (0.87 and 0.90 aw) suppressed the fungal growth, gene expression, and AFB1 production of A. flavus at all of the tested temperatures (20, 28, and 37 °C). The rapid drying of senna pods with a low water activity (≤0.87 aw) and storage at low temperature (20 °C) are ideal conditions to avoid AFB1 and ensure the quality of produce for export.
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Affiliation(s)
- Subramani Natarajan
- Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641 003, India
| | - Dananjeyan Balachandar
- Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641 003, India
| | - Natesan Senthil
- Department of Plant Molecular Biology and Bioinformatics, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641 003, India
| | - Vaikuntavasan Paranidharan
- Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641 003, India.
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Gasperini AM, Medina A, Magan N. Comparison of growth and aflatoxin B 1 production profiles of Aspergillus flavus strains on conventional and isogenic GM-maize-based nutritional matrices. Fungal Biol 2021; 126:82-90. [PMID: 34930561 DOI: 10.1016/j.funbio.2021.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 11/04/2022]
Abstract
Maize grown in both North and South America are now predominantly genetically modified (GM) cultivars with some resistance to herbicide, pesticide, or both. There is little information on the relative colonisation and aflatoxin B1 (AFB1) production with maize meal-based nutritional matrices based on kernels of non-GM maize and isogenic GM-ones by strains of Aspergillus flavus. The objectives were to examine the effect of interacting conditions of temperature (25-35 °C) and water availability (0.99-0.90 water activity, aw) on (a) mycelial growth, (b) AFB1 production and (c) develop contour maps of optimum and marginal conditions of these parameters for four strains of A. flavus on three different non-GM and isogenic GM-maize based nutritional media. The growth of the four strains of A. flavus (three aflatoxigenic; one non-aflatoxigenic) was relatively similar in relation to the temperature × aw conditions examined on both non-GM and GM-based matrices. Optimum growth overall was at 30-35 °C and 0.99 aw for all four strains. Under water stress (0.90 aw) growth was optimum at 35 °C. Statistically: non-GM, GM cultivars, temperature and aw all significantly affected growth rates. For AFB1 production, all single and interacting factors were statistically significant except for non-GM × GM cultivar. In conclusion, colonisation of GM- and non-GM nutritional sources was similar for the different A. flavus strains examined. The contour maps will be very useful for understanding the ecological niches for both toxigenic and non-toxigenic strains in the context of the competitive exclusion of those producing aflatoxins.
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Affiliation(s)
- Alessandra M Gasperini
- Applied Mycology Group, Environment and AgriFood Theme, Cranfield University, Cranfield, Beds, MK43 AL5, UK
| | - Angel Medina
- Applied Mycology Group, Environment and AgriFood Theme, Cranfield University, Cranfield, Beds, MK43 AL5, UK
| | - Naresh Magan
- Applied Mycology Group, Environment and AgriFood Theme, Cranfield University, Cranfield, Beds, MK43 AL5, UK.
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Galván AI, Rodríguez A, Martín A, Serradilla MJ, Martínez-Dorado A, Córdoba MDG. Effect of Temperature during Drying and Storage of Dried Figs on Growth, Gene Expression and Aflatoxin Production. Toxins (Basel) 2021; 13:toxins13020134. [PMID: 33670398 PMCID: PMC7918548 DOI: 10.3390/toxins13020134] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 01/29/2021] [Accepted: 02/02/2021] [Indexed: 11/28/2022] Open
Abstract
Dried fig is susceptible to infection by Aspergillus flavus, the major producer of the carcinogenic mycotoxins. This fruit may be contaminated by the fungus throughout the entire chain production, especially during natural sun-drying, post-harvest, industrial processing, storage, and fruit retailing. Correct management of such critical stages is necessary to prevent mould growth and mycotoxin accumulation, with temperature being one of the main factors associated with these problems. The effect of different temperatures (5, 16, 25, 30, and 37 °C) related to dried-fig processing on growth, one of the regulatory genes of aflatoxin pathway (aflR) and mycotoxin production by A. flavus, was assessed. Firstly, growth and aflatoxin production of 11 A. flavus strains were checked before selecting two strains (M30 and M144) for in-depth studies. Findings showed that there were enormous differences in aflatoxin amounts and related-gene expression between the two selected strains. Based on the results, mild temperatures, and changes in temperature during drying and storage of dried figs should be avoided. Drying should be conducted at temperatures >30 °C and close to 37 °C, while industry processing, storage, and retailing of dried figs are advisable to perform at refrigeration temperatures (<10 °C) to avoid mycotoxin production.
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Affiliation(s)
- Ana Isabel Galván
- Junta de Extremadura, Finca La Orden-Valdesequera Research Centre (CICYTEX), Horticulture, 06187 Guadajira, Spain;
| | - Alicia Rodríguez
- Food Quality and Microbiology, School of Agricultural Engineering, University of Extremadura, Avda. de Adolfo Suárez, s/n, 06007 Badajoz, Spain; (A.M.); (A.M.-D.); (M.d.G.C.)
- University Institute for the Research in Agrifood Resources (INURA), University of Extremadura, Avda. de la Investigación s/n, 06006 Badajoz, Spain
- Correspondence: ; Tel.: +34-924-289-300 (ext. 86283)
| | - Alberto Martín
- Food Quality and Microbiology, School of Agricultural Engineering, University of Extremadura, Avda. de Adolfo Suárez, s/n, 06007 Badajoz, Spain; (A.M.); (A.M.-D.); (M.d.G.C.)
- University Institute for the Research in Agrifood Resources (INURA), University of Extremadura, Avda. de la Investigación s/n, 06006 Badajoz, Spain
| | - Manuel Joaquín Serradilla
- Junta de Extremadura, Agri-Food Technological Institute of Extremadura (INTAEX-CICYTEX), Department of Postharvest Science Avda, 06007 Badajoz, Spain;
| | - Ana Martínez-Dorado
- Food Quality and Microbiology, School of Agricultural Engineering, University of Extremadura, Avda. de Adolfo Suárez, s/n, 06007 Badajoz, Spain; (A.M.); (A.M.-D.); (M.d.G.C.)
- University Institute for the Research in Agrifood Resources (INURA), University of Extremadura, Avda. de la Investigación s/n, 06006 Badajoz, Spain
| | - María de Guía Córdoba
- Food Quality and Microbiology, School of Agricultural Engineering, University of Extremadura, Avda. de Adolfo Suárez, s/n, 06007 Badajoz, Spain; (A.M.); (A.M.-D.); (M.d.G.C.)
- University Institute for the Research in Agrifood Resources (INURA), University of Extremadura, Avda. de la Investigación s/n, 06006 Badajoz, Spain
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Li J, Zhi QQ, Zhang J, Yuan XY, Jia LH, Wan YL, Liu QY, Shi JR, He ZM. Synthetic antimicrobial agents inhibit aflatoxin production. Braz J Microbiol 2021; 52:821-835. [PMID: 33447936 DOI: 10.1007/s42770-021-00423-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 01/05/2021] [Indexed: 11/25/2022] Open
Abstract
Antimicrobial peptides (AMPs) are biologically active molecules that can eradicate bacteria by destroying the bacterial membrane structure, causing the bacteria to rupture. However, little is known about the extent and effect of AMPs on filamentous fungi. In this study, we synthesized small molecular polypeptides by an inexpensive heat conjugation approach and examined their effects on the growth of Aspergillus flavus and its secondary metabolism. The antimicrobial agents significantly inhibited aflatoxin production, conidiation, and sclerotia formation in A. flavus. Furthermore, we found that the expression of aflatoxin structural genes was significantly inhibited, and the intracellular reactive oxygen species (ROS) level was reduced. Additionally, the antimicrobial agents can change membrane permeability. Overall, our results demonstrated that antimicrobial agents, safe to mammalian cells, have an obvious impact on aflatoxin production, which indicated that antimicrobial agents may be adopted as a new generation of potential agents for controlling aflatoxin contamination.
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Affiliation(s)
- Jing Li
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Qing-Qing Zhi
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Jie Zhang
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Xiao-Yu Yuan
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Li-Hong Jia
- The Guangdong Provincial Key Laboratory for Biotechnology Drug Candidates, School of Bioscience and Biopharmaceutics, Guangdong Pharmaceutical University, Guangzhou, 510006, China
| | - Yu-Lin Wan
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Qiu-Yun Liu
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China.
| | - Jian-Rong Shi
- Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology, Nanjing, 210000, China.
| | - Zhu-Mei He
- The Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China.
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Competitiveness of three biocontrol candidates against ochratoxigenic Penicillium nordicum under dry-cured meat environmental and nutritional conditions. Fungal Biol 2020; 125:134-142. [PMID: 33518203 DOI: 10.1016/j.funbio.2020.03.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 03/05/2020] [Accepted: 03/12/2020] [Indexed: 12/27/2022]
Abstract
The environmental conditions during the ripening of dry-cured meats and their nutritional composition promote the colonisation of their surface by Penicillium spp., including P. nordicum producer of ochratoxin A (OTA). The objective of this work was to study the competitiveness of three potential biocontrol candidates (Debaryomyces hansenii FHSCC 253H, Enterococcus faecium SE920 and Penicillium chrysogenum CECT, 20922) against the ochratoxigenic P. nordicum FHSCC4 under environmental and nutritional conditions simulating the ripening of dry-cured meat products. For this, the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays and OTA production were determined. The number of carbon sources (CSs) metabolised depended on the microorganism and the interacting water activity (aw) x temperature conditions. The number of CSs utilised by both filamentous fungi was quite similar and higher than those utilised by D. hansenii and E. faecium. The yeast isolate metabolised a number of CSs much larger than the bacterium. The NOI values showed that, in general, P. nordicum nutritionally dominated E. faecium and D. hansenii regardless of the environmental conditions evaluated. The relationship between the toxigenic and non-toxigenic fungal isolates depended on the aw x temperature combinations, although in none of the conditions a dominance of P. nordicum was observed. According to the interaction assays, both D. hansenii and P. chrysogenum decreased the growth of P. nordicum. The effect of D. hansenii could be attributed to the production of some extra-cellular compounds, while the action of P. chrysogenum is likely related to nutritional competition. In addition, both P. chrysogenum and D. hansenii reduced the OTA levels produced by P. nordicum. The effect of the yeast was more pronounced decreasing the concentration of OTA at quantities lower than the limit established by the Italian legislation. Therefore, P. chrysogenum and D. hansenii can be suggested as biocontrol candidates in the manufacture of dry-cured meat products.
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García-Díaz M, Gil-Serna J, Patiño B, García-Cela E, Magan N, Medina Á. Assessment of the Effect of Satureja montana and Origanum virens Essential Oils on Aspergillus flavus Growth and Aflatoxin Production at Different Water Activities. Toxins (Basel) 2020; 12:toxins12030142. [PMID: 32106532 PMCID: PMC7150974 DOI: 10.3390/toxins12030142] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 02/19/2020] [Accepted: 02/22/2020] [Indexed: 02/08/2023] Open
Abstract
Aflatoxin contamination of foodstuffs poses a serious risk to food security, and it is essential to search for new control methods to prevent these toxins entering the food chain. Several essential oils are able to reduce the growth and mycotoxin biosynthesis of toxigenic species, although their efficiency is strongly influenced by the environmental conditions. In this work, the effectiveness of Satureja montana and Origanum virens essential oils to control Aspergillus flavus growth was evaluated under three water activity levels (0.94, 0.96 and 0.98 aw) using a Bioscreen C, a rapid in vitro spectrophotometric technique. The aflatoxin concentrations at all conditions tested were determined by HPLC-FLD. Aspergillus flavus growth was delayed by both essential oil treatments. However, only S. montana essential oil was able to significantly affect aflatoxin production, although the inhibition percentages widely differed among water activities. The most significant reduction was observed at 0.96 aw, which is coincident with the conditions in which A. flavus reached the highest levels of aflatoxin production. On the contrary, the treatment with S. montana essential oil was not effective in significantly reducing aflatoxin production at 0.94 aw. Therefore, it is important to study the interaction of the new control compounds with environmental factors before their application in food matrices, and in vitro ecophysiological studies are a good option since they provide accurate and rapid results.
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Affiliation(s)
- Marta García-Díaz
- Department of Genetics, Physiology, and Microbiology, Faculty of Biology, University Complutense of Madrid, Jose Antonio Novais 12, 28040 Madrid, Spain; (M.G.-D.); (B.P.)
| | - Jessica Gil-Serna
- Department of Genetics, Physiology, and Microbiology, Faculty of Biology, University Complutense of Madrid, Jose Antonio Novais 12, 28040 Madrid, Spain; (M.G.-D.); (B.P.)
- Correspondence: (J.G.-S.); (Á.M.)
| | - Belén Patiño
- Department of Genetics, Physiology, and Microbiology, Faculty of Biology, University Complutense of Madrid, Jose Antonio Novais 12, 28040 Madrid, Spain; (M.G.-D.); (B.P.)
| | - Esther García-Cela
- Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK; (E.G.-C.); (N.M.)
- Biological and Environmental Sciences, School of Life and Medical Sciences, University of Hertfordshire, Hatfield AL109AB, UK
| | - Naresh Magan
- Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK; (E.G.-C.); (N.M.)
| | - Ángel Medina
- Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK; (E.G.-C.); (N.M.)
- Correspondence: (J.G.-S.); (Á.M.)
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Drott MT, Debenport T, Higgins SA, Buckley DH, Milgroom MG. Fitness Cost of Aflatoxin Production in Aspergillus flavus When Competing with Soil Microbes Could Maintain Balancing Selection. mBio 2019; 10:e02782-18. [PMID: 30782658 PMCID: PMC6381279 DOI: 10.1128/mbio.02782-18] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 01/08/2019] [Indexed: 02/08/2023] Open
Abstract
Selective forces that maintain the polymorphism for aflatoxigenic and nonaflatoxigenic individuals of Aspergillus flavus are largely unknown. As soils are widely considered the natural habitat of A. flavus, we hypothesized that aflatoxin production would confer a fitness advantage in the soil environment. To test this hypothesis, we used A. flavus DNA quantified by quantitative PCR (qPCR) as a proxy for fitness of aflatoxigenic and nonaflatoxigenic field isolates grown in soil microcosms. Contrary to predictions, aflatoxigenic isolates had significantly lower fitness than did nonaflatoxigenic isolates in natural soils across three temperatures (25, 37, and 42°C). The addition of aflatoxin to soils (500 ng/g) had no effect on the growth of A. flavus Amplicon sequencing showed that neither the aflatoxin-producing ability of the fungus nor the addition of aflatoxin had a significant effect on the composition of fungal or bacterial communities in soil. We argue that the fitness disadvantage of aflatoxigenic isolates is most likely explained by the metabolic cost of producing aflatoxin. Coupled with a previous report of a selective advantage of aflatoxin production in the presence of some insects, our findings give an ecological explanation for balancing selection resulting in persistent polymorphisms in aflatoxin production.IMPORTANCE Aflatoxin, produced by the fungus Aspergillus flavus, is an extremely potent hepatotoxin that causes acute toxicosis and cancer, and it incurs hundreds of millions of dollars annually in agricultural losses. Despite the importance of this toxin to humans, it has remained unclear what the fungus gains by producing aflatoxin. In fact, not all strains of A. flavus produce aflatoxin. Previous work has shown an advantage to producing aflatoxin in the presence of some insects. Our current work demonstrates the first evidence of a disadvantage to A. flavus in producing aflatoxin when competing with soil microbes. Together, these opposing evolutionary forces could explain the persistence of both aflatoxigenic and nonaflatoxigenic strains through evolutionary time.
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Affiliation(s)
- Milton T Drott
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, USA
| | - Tracy Debenport
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, USA
| | - Steven A Higgins
- School of Integrative Plant Science, Soil and Crop Sciences Section, Cornell University, Ithaca, New York, USA
| | - Daniel H Buckley
- School of Integrative Plant Science, Soil and Crop Sciences Section, Cornell University, Ithaca, New York, USA
| | - Michael G Milgroom
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, USA
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Yazid SNE, Thanggavelu H, Mahror N, Selamat J, Samsudin NIP. Formulation of maize- and peanut-based semi-synthetic growth media for the ecophysiological studies of aflatoxigenic Aspergillus flavus in maize and peanut agro-ecosystems. Int J Food Microbiol 2018; 282:57-65. [PMID: 29913332 DOI: 10.1016/j.ijfoodmicro.2018.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 06/01/2018] [Accepted: 06/08/2018] [Indexed: 10/14/2022]
Abstract
In studying the ecophysiology of fungal phytopathogens, several stages are involved (in vitro, greenhouse, in planta). Most in vitro studies extensively utilise the general growth media such as Potato Dextrose Agar and Malt Extract Agar. Although the crop components in these media serve as excellent carbon sources and yield luxuriant growth, they are not naturally contaminated with Aspergillus flavus and thus might result in under- or overestimation of its actual toxigenic potentials. Empirical data on the formulation of semi-synthetic growth medium mimicking the natural crop commonly contaminated by A. flavus for the ecophysiological studies in vitro are scarce. The present work was aimed at investigating the ecophysiology of A. flavus on commercial growth media (PDA, MEA); formulating maize- and peanut-based semi-synthetic growth media using two methods of raw material preparation (milling, hot water extraction) at different concentrations (1, 3, 5, 7, 9% w/v), and comparing the ecophysiological parameters between commercial and formulated growth media. Growth rates were obtained by computing the hyphal expansion data into y = mx + c equation. AFB1 was quantified using high performance liquid chromatography with fluorescence detector. Formulated media were found to yield significantly higher growth rates when compared to commercial media. However, commercial media yielded significantly higher AFB1 when compared to all formulated media. Between the two formulations, milling yielded significantly higher growth rates and AFB1 when compared to hot water extraction. Although in vitro data cannot directly extrapolate in planta performance, results obtained in the present work can be used to gauge the actual toxigenic potential of A. flavus in maize and peanut agro-ecosystems.
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Affiliation(s)
- Siti Nur Ezzati Yazid
- Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - Hemashangari Thanggavelu
- Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - Norlia Mahror
- Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - Jinap Selamat
- Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; Laboratory of Food Safety and Food Integrity, Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
| | - Nik Iskandar Putra Samsudin
- Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; Laboratory of Food Safety and Food Integrity, Institute of Tropical Agriculture and Food Security, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
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11
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Aldars-García L, Marín S, Sanchis V, Magan N, Medina A. Assessment of intraspecies variability in fungal growth initiation of Aspergillus flavus and aflatoxin B 1 production under static and changing temperature levels using different initial conidial inoculum levels. Int J Food Microbiol 2018; 272:1-11. [PMID: 29482078 DOI: 10.1016/j.ijfoodmicro.2018.02.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 01/06/2018] [Accepted: 02/11/2018] [Indexed: 11/24/2022]
Abstract
Intraspecies variability in fungal growth and mycotoxin production has important implications for food safety. Using the Bioscreen C we have examined spectrophotometrically intraspecies variability of A. flavus using 10 isolates under different environments, including temperature shifts, in terms of growth and aflatoxin B1 (AFB1) production. Five high and five low AFB1 producers were examined. The study was conducted at 5 isothermal conditions (from 15 to 37 °C) and 4 dynamic scenarios (between 15 and 30 °C). The experiments were carried out in a semisolid YES medium at 0.92 aw and two inoculum levels, 102 and 103 spores/mL. The Time to Detection (TTD) of growth initiation was determined and modelled as a function of temperature through a polynomial equation and the model was used to predict TTD under temperature upshifts conditions using a novel approach. The results obtained in this study have shown that a model can be developed to describe the effect of temperature upshifts on the TTD for all the studied isolates and inoculum levels. Isolate variability increased as the growth conditions became more stressful and with a lower inoculum level. Inoculum level affected the intraspecies variability but not the repeatability of the experiments. In dynamic conditions, isolate responses depended both on the temperature shift and, predominantly, the final temperature level. AFB1 production was highly variable among the isolates and greatly depended on temperature (optimum temperature at 30-35 °C) and inoculum levels, with often higher production with lower inoculum. This suggests that, from an ecological point of view, the potential isolate variability and interaction with dynamic conditions should be taken into account in developing strategies to control growth and predicting mycotoxin risks by mycotoxigenic fungi.
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Affiliation(s)
- Laila Aldars-García
- Food Technology Dept, XaRTA-UTPV, Agrotecnio Center, University of Lleida, Spain.
| | - Sonia Marín
- Food Technology Dept, XaRTA-UTPV, Agrotecnio Center, University of Lleida, Spain.
| | - Vicente Sanchis
- Food Technology Dept, XaRTA-UTPV, Agrotecnio Center, University of Lleida, Spain.
| | - Naresh Magan
- Applied Mycology Group, Environment and AgriFood Theme, Cranfield University, Cranfield, Bedford MK43 0AL, UK.
| | - Angel Medina
- Applied Mycology Group, Environment and AgriFood Theme, Cranfield University, Cranfield, Bedford MK43 0AL, UK.
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Medina A, Mohale S, Samsudin NIP, Rodriguez-Sixtos A, Rodriguez A, Magan N. Biocontrol of mycotoxins: dynamics and mechanisms of action. Curr Opin Food Sci 2017. [DOI: 10.1016/j.cofs.2017.09.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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13
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Bernáldez V, Córdoba JJ, Magan N, Peromingo B, Rodríguez A. The influence of ecophysiological factors on growth, aflR gene expression and aflatoxin B 1 production by a type strain of Aspergillus flavus. Lebensm Wiss Technol 2017. [DOI: 10.1016/j.lwt.2017.05.030] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Zhi QQ, Li JY, Liu QY, He ZM. A cytosine methyltransferase ortholog dmtA is involved in the sensitivity of Aspergillus flavus to environmental stresses. Fungal Biol 2017; 121:501-514. [DOI: 10.1016/j.funbio.2017.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 01/21/2017] [Accepted: 02/01/2017] [Indexed: 01/05/2023]
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15
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Samsudin NIP, Medina A, Magan N. Relationship between environmental conditions, carbon utilisation patterns and Niche Overlap Indices of the mycotoxigenic species Fusarium verticillioides and the biocontrol agent Clonostachys rosea. FUNGAL ECOL 2016. [DOI: 10.1016/j.funeco.2016.05.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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16
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Effects of temperature, water activity and incubation time on fungal growth and aflatoxin B1 production by toxinogenic Aspergillus flavus isolates on sorghum seeds. Rev Argent Microbiol 2016; 48:78-85. [PMID: 26920121 DOI: 10.1016/j.ram.2015.10.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2015] [Revised: 10/22/2015] [Accepted: 10/23/2015] [Indexed: 11/22/2022] Open
Abstract
Sorghum, which is consumed in Tunisia as human food, suffers from severe colonization by several toxigenic fungi and contamination by mycotoxins. The Tunisian climate is characterized by high temperature and humidity that stimulates mold proliferation and mycotoxin accumulation in foodstuffs. This study investigated the effects of temperature (15, 25 and 37°C), water activity (aw, between 0.85 and 0.99) and incubation time (7, 14, 21 and 28 d) on fungal growth and aflatoxin B1 (AFB1) production by three Aspergillus flavus isolates (8, 10 and 14) inoculated on sorghum grains. The Baranyi model was applied to identify the limits of growth and mycotoxin production. Maximum diameter growth rates were observed at 0.99 a(w) at 37°C for two of the isolates. The minimum aw needed for mycelial growth was 0.91 at 25 and 37°C. At 15°C, only isolate 8 grew at 0.99 a(w). Aflatoxin B1 accumulation could be avoided by storing sorghum at low water activity levels (≤0.91 a(w)). Aflatoxin production was not observed at 15°C. This is the first work on the effects of water activity and temperature on A. flavus growth and AFB1 production by A. flavus isolates on sorghum grains.
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Al-Saad LA, Al-Badran AI, Al-Jumayli SA, Magan N, Rodríguez A. Impact of bacterial biocontrol agents on aflatoxin biosynthetic genes, aflD and aflR expression, and phenotypic aflatoxin B₁ production by Aspergillus flavus under different environmental and nutritional regimes. Int J Food Microbiol 2015; 217:123-9. [PMID: 26513252 DOI: 10.1016/j.ijfoodmicro.2015.10.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 09/20/2015] [Accepted: 10/15/2015] [Indexed: 11/24/2022]
Abstract
The objectives of this study were to examine the efficacy of four bacterial antagonists against Aspergillus flavus using 50:50 ratio of bacterial cells/conidia for the control of aflatoxin B1 (AFB1) production on two different nutritional matrices, nutrient and maize-based media at different water availabilities (0.98, 0.94 water activity (aw) on nutrient medium; 0.995, 0.98 aw on maize meal agar medium) at 35°C. The indicators of efficacy used were the relative expression of one structural and regulatory gene in the biosynthetic pathway (aflD and aflR respectively) and the production of AFB1. These studies showed that some of the bacterial species could significantly inhibit the relative expression of the aflD and aflR genes at both 0.98 and 0.94 aw on nutrient agar. On maize-based media some of the bacterial antagonists reduced the activity of both genes at 0.94 aw and some at 0.995 aw. However, the results for AFB1 production were not consistent with the effects on gene expression. Some bacterial species stimulated AFB1 production on both nutrient and maize-based media regardless of aw. However, some bacterial treatments did inhibit AFB1 production significantly when compared to the control. Overall, this study suggests that temporal studies are required on the biosynthetic genes under different environmental and nutritional conditions to evaluate the potential of antagonists to control AFB1.
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Affiliation(s)
- Labeed A Al-Saad
- University of Basrah, College of sciences, Dept. of Biology, Iraq
| | | | | | - Naresh Magan
- Cranfield University, AgriFood Department, Applied Mycology Group, UK
| | - Alicia Rodríguez
- Cranfield University, AgriFood Department, Applied Mycology Group, UK.
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