Characterization and identification of aspergillus section flavi isolates from portuguese almonds using a polyphasic approach including MALDI-TOF ICMS
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abstract
Aspergillus is a large genus, with a complex and ever evolving taxonomy. Section Flavi is one of the most significant sections in the genus, and is one of the best studied among fungi, for the numerous industrial applications as well as for food safety issues.
Section Flavi is composed of a large number of very closely related species. While these species are difficult to differentiate morphologically and even genetically, they differ in a characteristic that is of paramount importance for food safety, as some are responsible for the production of the highly toxigenic aflatoxins. Taxonomy and species identification are therefore subject of great interest for scientists aiming to clarify the species concept and limits within the section. In this sense, the establishment of schemes for species and for aflatoxigenic strains identification that are simultaneously accurate, sensitive, robust and expedite is mandatory.
At present, reliable identification schemes typically imply the analysis of a wide variety of morphological, biochemical and molecular traits. Recently, Matrix-Assisted Laser Desorption/Ionisation Time-Of-Flight Intact Cell Mass Spectrometry (MALDI-TOF ICMS) has been used to generate spectra of protein masses in a range of 2,000 to 20,000 Da, which result in a taxa specific fingerprint. This technique has already shown high potentialities to discriminate very closely related taxa, but has rarely been used in fungal species identification, either on its one or as part of a polyphasic scheme of identification.
This work aimed to: i) characterize the population of Aspergillus section Flavi collected from Portuguese almonds in relation to their aflatoxigenic potential; ii) identify the isolates by applying a set of morphological, biochemical, molecular and spectral analyses (polyphasic approach); iii) compare the data obtained from the various approaches in terms of sensitivity, reliability and user-friendliness; and iii) determine the validity of MALDI-TOF technique for the identification of closely related field isolates of section Flavi.
