Front line defenders of the ecological niche : screeningthe structural diversity of peptaibiotics from saprotrophicand fungicolous Trichoderma/Hypocrea species

Abstract

Approximately 950 individual sequences of nonribosomally biosynthesised peptides are produced by the genus Trichoderma/Hypocreathat belong to a perpetually growing class of mostly linear antibiotic oligopeptides, which are rich in the non-proteinogenic alpha-aminoisobutyric acid (Aib). Thus, they are comprehensively named peptaibiotics. Notably, peptaibiotics represent ca. 80% of the total inventory of secondary metabolites currently known from Trichoderma/Hypocrea. Their unique membrane-modifying bioactivity results from amphipathicity and helicity, thus making them ideal candidates in assisting both colonisation and defence of the natural habitats by their fungal producers. Despite this, reports on the in vivo-detection of peptaibiotics have scarcely been published in the past. In order to evaluate the significance of peptaibiotic production for a broader range of potential producers, we screened nine specimens belonging to seven hitherto uninvestigated fungicolous or saprotrophic Trichoderma/Hypocrea species by liquid chromatography coupled to electrospray high resolution mass spectrometry. Sequences of peptaibiotics found were independently confirmed by analysing the peptaibiome of pure agar cultures.