ABSTRACT

Previous research on the identification of fungi by means of their Raman spectra (i.e. spectra based on the inelastic scattering of light) of their spores indicates that this approach could be a fast, cheap and reliable method to distinguish fungi. Entomopathogenic fungi are used in commercially available insecticides (mycoinsecticides), in particular species of the genera Beauveria and Metarhizium. The identification of fungi in infected organisms is necessary for efficacy studies as well as in environmental impact assessments. This study aims at developing a method to differentiate isolates of these fungi, more precisely isolates of Metarhizium brunneum (Ca8II, Cb15III, Cb16III), Metarhizium pemphigi (X1c) and Beauveria bassiana (DSM 62075) as a non-related reference. To this end, fungi were grown on different culture media (both artificial and natural); samples were taken at different ages of the culture to assess possible impacts of nutrition and age on conidial pigmentation. It was possible to obtain spectra from the conidia of these fungi. The final predictive model was capable of determining isolated conidia grown on model insects with an overall goodness of prediction of 98.8% without any further sample preparation. In conclusion, Raman microspectroscopy proves to be a reliable and fast approach to distinguish entomopathogenic fungi.

摘要

以前通过孢子的拉曼光谱（即基于光的非弹性散射的光谱）鉴定真菌的研究表明，这种方法可能是一种快速、廉价和可靠的真菌鉴别方法。昆虫病原真菌用于市售杀虫剂（mycoinsecticides），特别是白僵菌属和绿僵菌属的物种。鉴定受感染生物体中的真菌对于功效研究和环境影响评估是必要的。本研究旨在开发一种方法来区分这些真菌的分离物，更准确地说是绿僵菌(Ca8II、Cb15III、Cb16III)、天疱疮绿僵菌(X1c) 和白僵菌(DSM 62075) 作为非相关参考。为此，真菌在不同的培养基（人工和天然）上生长；在培养的不同年龄采集样本，以评估营养和年龄对分生孢子色素沉着的可能影响。有可能从这些真菌的分生孢子中获得光谱。最终的预测模型能够确定在模型昆虫上生长的分离的分生孢子，总体预测优度为 98.8%，无需任何进一步的样品制备。总之，拉曼显微光谱被证明是一种可靠且快速的方法来区分昆虫病原真菌。