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Hu K, Guo K, Wang X, Wang S, Li J, Li Q, Zhao N, Liu A, He L, Hu X, Yang Y, Zou L, Chen S, Liu S. Occurrence of ochratoxin A in Sichuan bacon from different geographical regions and characterization and biocontrol of ochratoxigenic Aspergillus westerdijkiae strain 21G2-1A. Food Res Int 2024; 184:114272. [PMID: 38609249 DOI: 10.1016/j.foodres.2024.114272] [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: 10/28/2023] [Revised: 03/20/2024] [Accepted: 03/22/2024] [Indexed: 04/14/2024]
Abstract
Sichuan bacon represents the most prevalent dry-cured meat product across Southwest China, but it is vulnerable to fungal spoilage. In the present study, a total of 47 Sichuan bacons were obtained from different regions of the Sichuan Province and analyzed for the presence of ochratoxin A (OTA), yielding a positive rate of 23.4 % (11/47). All the observed OTA concentrations exceeded the maximum admissible dose in meat products (1 μg/kg) established by some EU countries, with the highest OTA concentration being 250.75 μg/kg, which raises a food safety concern and reveals the need for a standardized scientific processing protocol. Then, an OTA-producing fungus named 21G2-1A was isolated from positive samples and found to be Aspergillus westerdijkiae. Further characterization suggested a positive correlation between fungal growth and OTA production. The optimal temperature for the former was 25 °C, while it was 20 °C for the latter. Although the A. westerdijkiae strain 21G2-1A demonstrated greater mycelium growth in the presence of NaCl, OTA production was significantly dismissed when the salinity was greater than 5 %. Four lactic acid bacteria (LAB) were screened out as antagonists against the ochratoxigenic fungus. In vitro evaluation of the antagonists revealed that live cells inhibited fungal growth, and adsorption also contributed to OTA removal at different levels. This study sheds some light on OTA control in Sichuan bacon through a biological approach.
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Affiliation(s)
- Kaidi Hu
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Keyu Guo
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Xingjie Wang
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Song Wang
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Jianlong Li
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Qin Li
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Ning Zhao
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Aiping Liu
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Li He
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Xinjie Hu
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Yong Yang
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China
| | - Likou Zou
- College of Resources, Sichuan Agricultural University, Chengdu, Sichuan 611130, People's Republic of China
| | - Shujuan Chen
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
| | - Shuliang Liu
- College of Food Science, Sichuan Agricultural University, Ya'an, Sichuan 625014, People's Republic of China.
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Tryfinopoulou P, Skarlatos L, Kaplani P, Panagou EZ. Antifungal activity of Saccharomyces cerevisiae and assessment of ochratoxigenic load on currants by means of Real Time PCR. Int J Food Microbiol 2021; 344:109111. [PMID: 33676331 DOI: 10.1016/j.ijfoodmicro.2021.109111] [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: 09/10/2020] [Revised: 02/02/2021] [Accepted: 02/15/2021] [Indexed: 10/22/2022]
Abstract
Currants are prone to contamination by ochratoxin during cultivation, processing and storage conditions. Saccharomyces cerevisiae is considered to be among the main species of grape yeast flora able to control antagonistic fungi. In this study, the potential of S. cerevisiae Y33 was investigated to inhibit the growth of several fungal species indigenous to the microbiota of grapes. Moreover, the efficacy of this yeast species was investigated to inhibit OTA by toxin producing fungi both in vitro and in situ. For this purpose thirty-five different fungal species, belonging to the genera Aspergillus, Penicillium, Cladosporium, Fusarium and Alternaria interacted in vitro with S. cerevisiae on Malt Extract agar plates, stored at 25 °C for 14 days. Results showed that the highest OTA producer A. carbonarius F71 was inhibited more than 99% from day 7, in contrast to A. niger strains that presented enhanced OTA production at day 14 due to interaction with S. cerevisiae Y33. Additionally, the antifungal potential of the selected yeast was also studied in situ on currants subjected to different treatments and stored at 25 °C for 28 days. Microbiological analysis was undertaken for the enumeration of the bacterial and fungal flora, together with OTA determination at 7 and 21 days. To quantify A. carbonarius on all treated currant samples, molecular analysis with Real Time PCR was employed. A standard curve was prepared with A. carbonarius DNA. The efficiency of the curve was estimated to 10.416, the slope to -3.312 and the range of haploid genome that could be estimated was from 1.05 to 105∙105. The amount of A. carbonarius DNA in all treated currants samples, where the fungus was positively detected, ranged from as low as 0.08 to 562 ng DNA/g currants. The antifungal activity of S. cerevisiae Y33 was observed in all studied cases, causing inhibition of fungal growth and OTA production.
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Affiliation(s)
- Paschalitsa Tryfinopoulou
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, School of Food and Nutritional Sciences, Agricultural University of Athens, Iera Odos 75, 11855, Greece
| | - Leonidas Skarlatos
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, School of Food and Nutritional Sciences, Agricultural University of Athens, Iera Odos 75, 11855, Greece
| | - Paraskevi Kaplani
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, School of Food and Nutritional Sciences, Agricultural University of Athens, Iera Odos 75, 11855, Greece
| | - Efstathios Z Panagou
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, School of Food and Nutritional Sciences, Agricultural University of Athens, Iera Odos 75, 11855, Greece.
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Abdo H, Catacchio CR, Ventura M, D'Addabbo P, Alexandre H, Guilloux-Bénatier M, Rousseaux S. The establishment of a fungal consortium in a new winery. Sci Rep 2020; 10:7962. [PMID: 32409784 PMCID: PMC7224177 DOI: 10.1038/s41598-020-64819-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 04/15/2020] [Indexed: 01/03/2023] Open
Abstract
The biodiversity and evolution of fungal communities were monitored over a period of 3 vintages in a new winery. Samples were collected before grape receipt and 3 months after fermentation from 3 different wine related environments (WRE): floor, walls and equipment and analyzed using Illumina Mi-Seq. Genera of mold and filamentous fungi (294), non-enological (10) and wine-associated yeasts (25) were detected on all WREs before the arrival of the first harvest. Among them, genera like Alternaria and Aureobasidium persisted during two vintages. Therefore, these genera are not specific to winery environment and appear to be adapted to natural or anthropic environments due to their ubiquitous character. Some genera like Candida were also detected before the first harvest but only on one WREs, whereas, on the other WREs they were found after the harvest. The ubiquitous character and phenotypic traits of these fungal genera can explain their dynamics. After the first harvest and during 3 vintages the initial consortium was enriched by oenological genera like Starmerella introduced either by harvest or by potential transfers between the different WREs. However, these establishing genera, including Saccharomyces, do not appear to persist due to their low adaptation to the stressful conditions of winery environment.
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Affiliation(s)
- Hany Abdo
- Université Bourgogne Franche-Comté, AgroSup Dijon, PAM UMR A 02.102, F-21000 Dijon, France- IUVV Equipe VAlMiS, rue Claude Ladrey, BP 27877, 21078, Dijon, Cedex, France
| | | | - Mario Ventura
- Department of Biology, University of Bari, Bari, 70125, Italy
| | | | - Hervé Alexandre
- Université Bourgogne Franche-Comté, AgroSup Dijon, PAM UMR A 02.102, F-21000 Dijon, France- IUVV Equipe VAlMiS, rue Claude Ladrey, BP 27877, 21078, Dijon, Cedex, France
| | - Michèle Guilloux-Bénatier
- Université Bourgogne Franche-Comté, AgroSup Dijon, PAM UMR A 02.102, F-21000 Dijon, France- IUVV Equipe VAlMiS, rue Claude Ladrey, BP 27877, 21078, Dijon, Cedex, France
| | - Sandrine Rousseaux
- Université Bourgogne Franche-Comté, AgroSup Dijon, PAM UMR A 02.102, F-21000 Dijon, France- IUVV Equipe VAlMiS, rue Claude Ladrey, BP 27877, 21078, Dijon, Cedex, France.
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Gerin D, González-Candelas L, Ballester AR, Pollastro S, De Miccolis Angelini RM, Faretra F. Functional Characterization of the alb1 Orthologue Gene in the Ochratoxigenic Fungus Aspergillus carbonarius (AC49 strain). Toxins (Basel) 2018. [PMID: 29534508 PMCID: PMC5869408 DOI: 10.3390/toxins10030120] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Aspergillus carbonarius, belonging to the group Nigri, is the main species responsible for contamination by ochratoxin A (OTA) in grapes and derivative products. OTA can accumulate in the mycelium and in black conidia of the fungus and released into the matrix. Here, we have deleted in A. carbonarius the alb1 orthologue gene of A. fumigatus, involved in melanin biosynthesis. Three A. carbonarius Δalb1 mutants were characterized for morphologic traits and OTA production on different media and temperatures. Δalb1 mutants showed a fawn color of conidia associated with a significant reduction of the conidiogenesis and a statistically significant increase (p ≤ 0.01) of total OTA production as compared to the wild type (WT) strain. The alb1 gene somehow affected OTA partitioning since in Δalb1 mutants OTA amount was lower in conidia and was more abundantly secreted into the medium as compared to the WT. On grape berries the Δalb1 mutants and the WT caused lesions with similar sizes but OTA amount in berry tissues was higher for the mutants. These results demonstrate that A. carbonarius conidia pigmentation is largely dependent on polyketide biosynthesis. The gene is not directly involved in virulence and its deletion affects morphological features and OTA production in the fungus.
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Affiliation(s)
- Donato Gerin
- Department of Soil, Plant and Food Sciences, University of Bari Aldo Moro, via Amendola 165/A, 70126 Bari, Italy.
| | - Luis González-Candelas
- Instituto de Agroquímica y Tecnología de Alimentos, IATA-CSIC, Calle Agustín Escardino 7, Paterna, 46980 Valencia, Spain.
| | - Ana-Rosa Ballester
- Instituto de Agroquímica y Tecnología de Alimentos, IATA-CSIC, Calle Agustín Escardino 7, Paterna, 46980 Valencia, Spain.
| | - Stefania Pollastro
- Department of Soil, Plant and Food Sciences, University of Bari Aldo Moro, via Amendola 165/A, 70126 Bari, Italy.
- SELGE Network of Public Research Laboratories, via Amendola 165/A, 70126 Bari, Italy.
| | - Rita Milvia De Miccolis Angelini
- Department of Soil, Plant and Food Sciences, University of Bari Aldo Moro, via Amendola 165/A, 70126 Bari, Italy.
- SELGE Network of Public Research Laboratories, via Amendola 165/A, 70126 Bari, Italy.
| | - Francesco Faretra
- Department of Soil, Plant and Food Sciences, University of Bari Aldo Moro, via Amendola 165/A, 70126 Bari, Italy.
- SELGE Network of Public Research Laboratories, via Amendola 165/A, 70126 Bari, Italy.
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Hashem A, Fathi Abd-Allah E, Sultan Al-Obeed R, Abdullah Alqarawi A, Alwathnani HA. Effect of Carbon, Nitrogen Sources and Water Activity on Growth and Ochratoxin Production of Aspergillus carbonarius (Bainier) Thom. Jundishapur J Microbiol 2015; 8:e17569. [PMID: 25825649 PMCID: PMC4362018 DOI: 10.5812/jjm.17569] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 05/13/2014] [Accepted: 05/22/2014] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Ochratoxin A (OTA) is a toxic secondary metabolite produced by fungi belonging to Aspergillus and Penicillium genera. The production of OTA is influenced by environmental conditions and nutritional requirements. The postharvest application of bunches of table grape fruit (TGF), with water activity of 0.8 aw, was highly effective for controlling OTA contamination in vitro and in vivo (table grape). OBJECTIVES The aim of this study was to determine the influence of environmental conditions and nutritional requirements on growth and OTA production by Aspergillus carbonarius, as well as, the impact of water activity on OTA production and growth characters of A. carbonarius. Furthermore, we also examined the influence of the application of different levels of water activity (aw 0.8) on the preservation of the general appearance of TGF and control of their contamination with OTA. MATERIALS AND METHODS The growth and OTA production by A. carbonarius were studied using glucose-ammonium nitrate salt broth medium. Effect of water activity was studied using glycerol (0.80, 0.85, 0.90, and 0.98 aw). The bunches of table grape fruits were immersed in glycerol solution (equivalent to 0.80 aw) and placed as a double layer in cardboard boxes (25 × 35 × 10 cm). The boxes were stored at 20°C for 15 days to simulate local market conditions. RESULTS The maximum OTA production by A. carbonarius was observed on broth medium after eight days of incubation at 20°C, with pH 4, and fructose and ammonium nitrate supplementation as carbon and nitrogen sources, respectively. The water activity (0.9, 0.85 aw) caused significant decrease in OTA production by A. carbonarius. The postharvest application of water activity (0.8 aw) was highly effective for maintenance of the table grape quality, which was expressed as weight loss, firmness and decay, while it also controlled OTA contamination of fruits under concept of local market conditions. CONCLUSIONS Our results reported that deterioration of TGF by A. carbonarius could be minimized by application of aw. Our experiments were performed under conditions of local markets, which support the economy of many thousands of families in Egypt, especially in the poor rural areas. In future adequate research is required to use these technologies commercially.
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Affiliation(s)
- Abeer Hashem
- Department of Mycology and Plant Disease Survey, Plant Pathology Research Institute, Agriculture Research Center, Giza, Egypt
| | - Elsayed Fathi Abd-Allah
- Plant Production Department, Faculty of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Rashid Sultan Al-Obeed
- Plant Production Department, Faculty of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Abdulaziz Abdullah Alqarawi
- Plant Production Department, Faculty of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Hend Awad Alwathnani
- Botany and Microbiology Department, Faculty of Science, King Saud University, Riyadh, Saudi Arabia
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Camardo Leggieri M, Mitchell D, Aldred D, Battilani P, Magan N. Hydro- and thermotimes for conidial germination kinetics of the ochratoxigenic species Aspergillus carbonarius in vitro, on grape skin and grape flesh. Fungal Biol 2014; 118:996-1003. [PMID: 25457947 DOI: 10.1016/j.funbio.2014.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 09/16/2014] [Accepted: 09/26/2014] [Indexed: 11/18/2022]
Abstract
The objective was to compare the ability of spores of Aspergillus carbonarius to germinate in vitro, in situ on grape skin and grape flesh in relation to temperature (15-40 °C) and different relative humidities (100-85% RH). Spores were inoculated as a spore suspension (10(6) spores ml(-1)) onto the surface of white organic grapes and directly onto cut grape flesh. For comparison, spores were spread plate onto a synthetic grape juice medium (SGM) modified to the equivalent water activity (a(w)) range of 0.995-0.85. This showed that conidia germinated more rapidly on grape flesh (6 h) followed by that on the SGM medium (9 h) and then grape skin (24 h) under optimal condition of 30-35 °C and 100 % RH. At marginal conditions, such as 15 °C and 85-90% RH, germination was very slow. The time to 5% germination was significantly shorter on grape flesh than in vitro on grape medium and slowest on grape skin. This suggests that damaged grapes provide the main method of infection and contamination of grapes and grape products with ochratoxin A (OTA). The combined effect of temperature and RH on conidial germination of A. carbonarius on SGM and grape skin was described by combining Beta and polynomial equations. The equations developed in this work provided a good fit of the biological processes; they could be integrated in a predictive model for infection and OTA prediction in ripening grapes.
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Affiliation(s)
- Marco Camardo Leggieri
- Institute of Entomology and Plant Pathology, Università Cattolica del Sacro Cuore, via Emilia Parmense 84, 29100 Piacenza, Italy
| | - David Mitchell
- Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK
| | - David Aldred
- Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK
| | - Paola Battilani
- Institute of Entomology and Plant Pathology, Università Cattolica del Sacro Cuore, via Emilia Parmense 84, 29100 Piacenza, Italy
| | - Naresh Magan
- Applied Mycology Group, Cranfield Soil and AgriFood Institute, Cranfield University, Bedford MK43 0AL, UK.
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Pei R, Gunsch CK. Inflammatory cytokine gene expression in THP-1 cells exposed to Stachybotrys chartarum and Aspergillus versicolor. ENVIRONMENTAL TOXICOLOGY 2013; 28:51-60. [PMID: 21384497 PMCID: PMC3733268 DOI: 10.1002/tox.20698] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Revised: 12/21/2010] [Accepted: 12/27/2010] [Indexed: 05/30/2023]
Abstract
Very little is known about the mechanisms that occur in human cells upon exposure to fungi as well as their mycotoxins. A better understanding of toxin-regulated gene expression would be helpful to identify safe levels of exposure and could eventually be the basis for establishing guidelines for remediation scenarios following a water intrusion event. In this research, cytokine mRNA expression patterns were investigated in the human monocytic THP-1 cell line exposed to fungal extracts of various fragment sizes obtained from Stachybotrys chartarum RTI 5802 and/or Aspergillus versicolor RTI 3843, two common and well-studied mycotoxin producing fungi. Cytokine mRNA expression was generally upregulated 2-10 times following a 24 h exposure to fungal extracts. Expression of the proinflammatory interleukin-1β, interleukin-8, and tumor necrosis factor-α genes increased while the anti-inflammatory gene interleukin-10 also increased albeit at very low level, suggesting that negative feedback regulation mechanism of production of proinflammatory cytokines initiated upon 24 h of incubation. In addition, submicron size extracts of A. versicolor caused significant death of THP-1 cells, whereas extracts of S. chartarum caused no cell death while the mixture of the two fungi had an intermediate effect. There was no general correlation between gene expression and fragment sizes, which suggests that all submicron fragments may contribute to inflammatory response.
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Affiliation(s)
| | - Claudia K. Gunsch
- Corresponding author. Department of Civil and Environmental Engineering, Duke University, Box 90287, Durham, NC 27708-0287, USA. Tel.: (919) 660-5208, fax: (919) 660-5219.
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Meyvaci KB, Aksoy U, Eltem R, Altindişli A, Aşkun T, Taşkin E. Effect of yearly conditions and management practices on ochratoxin A production in Sultana Seedless vineyards. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2012; 29:1157-67. [PMID: 22545668 DOI: 10.1080/19440049.2012.681399] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Sun drying of seedless grapes (Vitis vinifera cv. Sultanina) is widely practised in the western Aegean Region providing Turkey with a significant share in the world trade of sultanas. Research was initiated in 1998 to determine the incidence of ochratoxin A (OTA), to identify the major factors resulting in contamination and to develop techniques to reduce or prevent contamination. This paper assesses OTA formation in five experimental vineyards located in Manisa province of Turkey between 1998 and 2003. The cultural practices recorded were tillage (type and timing), fertilisation, plant protection, irrigation, trellising, pruning, GA(3) application, harvest maturity and date, and drying practices (type of drying yard, dipping into alkaline solution, length of drying period). In the experimental vineyards, no OTA was found at veraison. OTA levels in grapes harvested at fresh maturity ranged between <LOD and 8 ng g(-1), whereas in dried sultanas they were between <LOD and 35 ng g(-1). The frequency of OTA-positive samples increased in dried grapes compared with fresh. The number and timing of tillage, number of damaged berries, and removal of damaged/infected berries prior to sun drying were identified as the major good practices that may contribute to the reduction of OTA in sultanas.
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Affiliation(s)
- K B Meyvaci
- Department of Horticulture, Faculty of Agriculture, Ege University, 35100 Bornova-İzmir, Turkey.
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Giorni P, Camardo Leggieri M, Magan N, Battilani P. Comparison of temperature and moisture requirements for sporulation of Aspergillus flavus sclerotia on natural and artificial substrates. Fungal Biol 2012; 116:637-42. [PMID: 22658309 DOI: 10.1016/j.funbio.2012.03.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 03/20/2012] [Accepted: 03/21/2012] [Indexed: 11/26/2022]
Abstract
A key step in the infection cycle by Aspergillus flavus in maize is sporulation of sclerotia present in soil or in crop debris. However, little information is available on this critical and important phase. This study included experiments on artificial (Czapek Dox Agar (CZ)) and natural (maize stalks) substrates under different conditions of temperature (T; from 5 to 45 °C) and water activity (a(w); from 0.50 to 0.99) levels to quantify sporulation from sclerotia. The mean numbers of spores were higher on defined nutritional medium in vitro on CZ agar than on maize stalks (4.5×10(6) spores/sclerotium versus 4.2×10(4) spores/sclerotium) with production initiated after 6 and 24h, respectively. Surprisingly, the optimal temperature was found at 30-35 °C for CZ agar (9.23×10(6) spores/sclerotium) and to be 20-25 °C for maize stalks (6.26×10(4) spores/sclerotium). Water stress imposition only reduced sporulation at ≤0.90 a(w.) With more available water no significant differences were found between 0.90 and 0.99 a(w). This type of data is critical in the development of a mechanistic model to predict the infection cycle of A. flavus in maize in relation to meteorological conditions.
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Affiliation(s)
- Paola Giorni
- Institute of Entomology and Plant Pathology, Università Cattolica del Sacro Cuore, via E. Parmense 84, 29122 Piacenza, Italy
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Submerged conidiation and product formation by Aspergillus niger at low specific growth rates are affected in aerial developmental mutants. Appl Environ Microbiol 2011; 77:5270-7. [PMID: 21652743 DOI: 10.1128/aem.00118-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Exposure to an aerial environment or severe nutrient limitation induces asexual differentiation in filamentous fungi. Submerged cultivation of Aspergillus niger in carbon- and energy-limited retentostat cultures both induces and fuels conidiation. Physiological and transcriptomic analyses have revealed that this differentiation strongly affects product formation. Since conidiation is inherent in the aerial environment, we hypothesized that product formation near zero growth can be influenced by affecting differentiation or development of aerial hyphae in general. To investigate this idea, three developmental mutants (ΔfwnA, scl-1, and scl-2 mutants) that have no apparent vegetative growth defects were cultured in maltose-limited retentostat cultures. The secondary-metabolite profile of the wild-type strain defined flavasperone, aurasperone B, tensidol B, and two so far uncharacterized compounds as associated with conidium formation, while fumonisins B(2), B(4), and B(6) were characteristic of early response to nutrient limitation by the vegetative mycelium. The developmental mutants responded differently to the severe substrate limitation, which resulted in distinct profiles of growth and product formation. fwnA encodes the polyketide synthase responsible for melanin biosynthesis during aerial differentiation, and we show that conidial melanin synthesis in submerged retentostat cultures and aurasperone B production are fwnA dependent. The scl-1 and scl-2 strains are two UV mutants generated in the ΔfwnA background that displayed reduced asexual conidiation and formed sclerotium-like structures on agar plates. The reduced conidiation phenotypes of the scl-1 and scl-2 strains are reflected in the retentostat cultivation and are accompanied by elimination or severely reduced accumulation of secondary metabolites and distinctly enhanced accumulation of extracellular protein. This investigation shows that submerged conidiation and product formation of a mitosporic fungus cultured at low specific growth rates can be fundamentally affected by interfering with the genetic program for differentiation of aerial hyphae, opening new perspectives for tailoring industrial performance.
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Alborch L, Bragulat M, Abarca M, Cabañes F. Temperature and incubation time effects on growth and ochratoxin A production by Aspergillus sclerotioniger and Aspergillus lacticoffeatus on culture media. Lett Appl Microbiol 2011; 52:208-12. [DOI: 10.1111/j.1472-765x.2010.02983.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Gallo A, Perrone G, Solfrizzo M, Epifani F, Abbas A, Dobson ADW, Mulè G. Characterisation of a pks gene which is expressed during ochratoxin A production by Aspergillus carbonarius. Int J Food Microbiol 2008; 129:8-15. [PMID: 19038469 DOI: 10.1016/j.ijfoodmicro.2008.10.022] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Revised: 10/21/2008] [Accepted: 10/23/2008] [Indexed: 11/17/2022]
Abstract
Aspergillus carbonarius is considered the main fungus responsible for ochratoxin A (OTA) contamination in grapes. OTA is a potent nephrotoxin and a possible human carcinogen with a polyketide derived structure. Fungal polyketide synthases (PKSs) have recently been demonstrated to be involved in OTA biosynthesis in both Penicillium and Aspergillus species. We report here on the identification and characterisation of part of a novel polyketide synthase gene, ACpks from A. carbonarius. The sequence appears to encode conserved ketosynthase and acyl transferase domains, which are characteristic of previously characterised PKS enzymes. Expression of the ACpks gene is differentially regulated, with transcription being observed when the fungus was grown on synthetic grape medium and on OTA permissive medium (MM) whereas no transcription was detected when the fungus was grown on OTA restrictive medium (YES). ACpks expression was also observed when A. carbonarius was grown at low pH, with concomitant increases in OTA production. This correlation between ACpks gene expression and OTA production suggests the likely involvement for the product of this gene in ochratoxin A biosynthesis in the fungus. From a preliminary screening of Aspergillus isolates with ACpks specific primers, ACpks gene homologues appear to be present in A. sclerotioniger and A. ibericus, two species of section Nigri which are closely related to A. carbonarius.
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Affiliation(s)
- Antonia Gallo
- Institute of Sciences of Food Production, ISPA-CNR, Bari, Italy.
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