Abstract

The dichlorvos-ammonia (DV-AM) method is a simple but sensitive visual method for detecting aflatoxigenic fungi. Here we sought to develop a selective medium that is appropriate for the growth of aflatoxigenic fungi among soil mycoflora. We examined the effects of different concentrations of carbon sources (sucrose and glucose) and detergents (deoxycholate (DOC), Triton X-100, and Tween 80) on microorganisms in soils, using agar medium supplemented with chloramphenicol. The results demonstrated that 5–10% sucrose concentrations and 0.1–0.15% DOC concentrations were appropriate for the selective detection of aflatoxigenic fungi in soil. We also identified the optimal constituents of the medium on which the normal rapid growth of Rhizopus sp. was completely inhibited. By using the new medium along with the DV-AM method, we succeeded in the isolation of aflatoxigenic fungi from non-agricultural fields in Fukui city, Japan. The fungi were identified as Aspergillus nomius based on their calmodulin gene sequences. These results indicate that the new medium will be useful in practice for the detection of aflatoxigenic fungi in soil samples including those from non-agricultural environments.

Highlights

  • Aflatoxins (AFs) are highly toxic, carcinogenic, and teratogenic secondary metabolites produced by fungi [1]

  • We previously developed a sensitive and simple visual[19,20,21,22], detection method, the dichlorvos-ammonia assay (ELISA) [23,24,25,26,27,28], and other methods; (3) the identification of aflatoxigenic fungi using a (DV-AM) method [32], in which fungi are first cultured on AF-inducible agar medium supplemented polymerase chain reaction (PCR) or a real-time PCR [29,30,31], and other methods

  • The color change of the colony is due to color changes of aflatoxin precursors, i.e., versiconal fungi were isolated from sorghum fields in Japan [34], and that this method was useful for the hemiacetal acetate (VHA) and versiconol acetate (VOAc), which accumulate in the mycelia by the isolation of aflatoxigenic as well asenzyme, atoxigenic fungi fromby soils a maize inhibition of an AF biosynthetic esterase, DV of

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Summary

Introduction

Aflatoxins (AFs) are highly toxic, carcinogenic, and teratogenic secondary metabolites produced by fungi [1]. Many have reported the isolation of aflatoxigenic fungisection from the soil in fields (e.g., cotton, peanutneed and maize fields), and by theanother researchers usuallymethod used multiple fungi to produce aflatoxins to be confirmed analytical notedprocedures: in method (2) These are useful and fruitful are time-consuming and often require some medium [16], modified rose. The color change of the colony is due to color changes of aflatoxin precursors, i.e., versiconal fungi were isolated from sorghum fields in Japan [34], and that this method was useful for the hemiacetal acetate (VHA) and versiconol acetate (VOAc), which accumulate in the mycelia by the isolation of aflatoxigenic as well asenzyme, atoxigenic fungi fromby soils a maize inhibition of an AF biosynthetic esterase, DV of

Results
The Effect of Detergents in the Media
Method
Discussion
Conclusions
Microorganisms
DV-AM Method
Collection and Storage of Soils
The Morphology of the Aflatoxigenic Fungi in FUT Soil
Recovery of Aflatoxigenic Fungi from Soils by the DV-AM Method
Characterization of the Isolated Fungi
Identification of the Fungi

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