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The production of aflatoxin B1 or G1 by Aspergillus parasiticus at various combinations of temperature and water activity is related to the ratio of aflS to aflR expression

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Abstract

The influence of varying combinations of water activity (aw) and temperature on growth, aflatoxin biosynthesis and aflR/aflS expression of Aspergillus parasiticus was analysed in the ranges 17–42°C and 0.90–0.99 aw. Optimum growth was at 35°C. At each temperature studied, growth increased from 0.90 to 0.99 aw. Temperatures of 17 and 42°C only supported marginal growth. The external conditions had a differential effect on aflatoxin B1 or G1 biosynthesis. The temperature optima of aflatoxin B1 and G1 were not at the temperature which supported optimal growth (35°C) but either below (aflatoxin G1, 20–30°C) or above (aflatoxin B1, 37°C). Interestingly, the expression of the two regulatory genes aflR and aflS showed an expression profile which corresponded to the biosynthesis profile of either B1 (aflR) or G1 (aflS). The ratios of the expression data between aflS:aflR were calculated. High ratios at a range between 17 and 30°C corresponded with the production profile of aflatoxin G1 biosynthesis. A low ratio was observed at >30°C, which was related to aflatoxin B1 biosynthesis. The results revealed that the temperature was the key parameter for aflatoxin B1, whereas it was water activity for G1 biosynthesis. These differences in regulation may be attributed to variable conditions of the ecological niche in which these species occur.

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Acknowledgement

We would like to thank Katja Kramer and Sabine Häckel for excellent technical assistance. This work was supported by the EU project EC KBBE-2007-222690-2 MYCORED.

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Authors and Affiliations

  1. Max Rubner Institut, Haid-und-Neu-Str. 9, 76131, Karlsruhe, Germany

    Markus Schmidt-Heydt, Corinna E. Rüfer & Rolf Geisen

  2. Applied Mycology Group, Cranfield Health, Cranfield University, Bedford, MK43 0AL, UK

    Ahmed Abdel-Hadi & Naresh Magan

Authors
  1. Markus Schmidt-Heydt
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  2. Corinna E. Rüfer
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  3. Ahmed Abdel-Hadi
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  4. Naresh Magan
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  5. Rolf Geisen
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Correspondence to Rolf Geisen.

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Schmidt-Heydt, M., Rüfer, C.E., Abdel-Hadi, A. et al. The production of aflatoxin B1 or G1 by Aspergillus parasiticus at various combinations of temperature and water activity is related to the ratio of aflS to aflR expression. Mycotox Res 26, 241–246 (2010). https://doi.org/10.1007/s12550-010-0062-7

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  • DOI: https://doi.org/10.1007/s12550-010-0062-7

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