Max Rubner Institut, Haid-und-Neu-Str. 9, 76131, Karlsruhe, Germany.
Mycotoxin Res. 2010 Nov;26(4):241-6. doi: 10.1007/s12550-010-0062-7. Epub 2010 Jul 27.
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.
研究了水分活度（aw）和温度在 17-42°C 和 0.90-0.99 aw 范围内变化组合对寄生曲霉生长、黄曲霉毒素生物合成和 aflR/aflS 表达的影响。最佳生长温度为 35°C。在所研究的每个温度下，生长都从 aw0.90 增加到 aw0.99。17°C 和 42°C 的温度仅支持边缘生长。外部条件对黄曲霉毒素 B1 或 G1 生物合成有不同的影响。黄曲霉毒素 B1 和 G1 的最佳温度不在支持最佳生长（35°C）的温度下，而是低于（黄曲霉毒素 G1，20-30°C）或高于（黄曲霉毒素 B1，37°C）。有趣的是，两个调节基因 aflR 和 aflS 的表达谱与 B1（aflR）或 G1（aflS）的生物合成谱相对应。计算了 aflS:aflR 表达数据之间的比值。在 17-30°C 之间的高比值与黄曲霉毒素 G1 生物合成的生产谱相对应。在>30°C 时观察到低比值，这与黄曲霉毒素 B1 生物合成有关。结果表明，温度是黄曲霉毒素 B1 的关键参数，而水活度是 G1 生物合成的关键参数。这些调控差异可能归因于这些物种所处生态位的条件变化。
