Inhibitory Effects of Indole on the Mycelial Growth and Aflatoxin B1 Production of Aspergillus flavus
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Abstract:
The inhibitory effects of indole on the mycelial growth and aflatoxin B1 production of Aspergillus flavus were investigated in this study. It was found that indole could efficiently inhibit the growth of A. flavus in a 96-well plate with the minimum inhibitory concentration (MIC) value of 100 μg/mL. Furthermore, the difference method was used to determine the inhibitory effects of indole on the mycelial weight of A. flavus. The results showed that 200 μg/mL indole could lead to the complete arrest of A. flavus mycelial growth. In addition, high performance liquid chromatography (HPLC) analysis showed that when the indole concentration was 50 μg/mL, the production of aflatoxin B1 was effectively inhibited whereas no significant impacts were observed on the mycelial growth of A. flavus. These results indicate that the inhibition of aflatoxin B1 production by indole is not achieved by inhibiting the mycelial growth of A. flavus. To further understand the mechanism underlying the inhibition of aflatoxin B1 production, reverse transcription polymerase chain reaction (RT-PCR) was performed to analyze the effects of indole on the expression of genes relevant to aflatoxin production. The results showed that indole exerted the same impacts on the expression of aflR- the regulatory gene in aflatoxin biosynthesis- as on aflatoxin B1 production. Additionally, indole could also downregulate the expression of aflD and aflK that are related to aflatoxin production. In summary, our results indicate that indole can be a potential candidate for application in the control of A. flavus contamination in food and animal feed.
