Recent Advances and Future Prospects in Peptaibiotics, Hydrophobin, and Mycotoxin Research, and Their Importance for Chemotaxonomy of Trichoderma and Hypocrea

Abstract

Fungi of the genus Trichoderma with teleomorphs in Hypocrea are abundant producers of a group of amphiphilic, non-ribosomal peptide antibiotics, which are rich in the non-proteinogenic amino acid Aib (alpha-aminoisobutyric acid). They are referred to as peptaibiotics, or peptaibols, if a 1,2-amino alcohol is present at the C-terminus. Trichoderma/Hypocrea, like other ascomycetous fungi, also produce hydrophobins, a class of small, cysteine-rich proteins. Advanced soft ionization mass spectrometric techniques such as LC-CID-MS, LC-ESI-MS(n), and IC-MALDI-TOF-MS enabled the high-throughput analysis, simultaneous detection and sequence determination of peptaibiotics and hydrophobins from minute quantities of fungal materials. Some Trichoderma species have been recognized to produce peptaibiotics as well as simple mycotoxins of the trichothecene group. The combination of sequence data of both groups of peptides with the pattern of low-molecular-weight secondary metabolites, including trichothecene-type mycotoxins, independently confirmed the results of morphological, molecular, and phylogenetic analyses. This approach established a new lineage in Trichoderma/Hypocrea, the Brevicompactum clade, comprising four new and one redescribed species. Notably, commercial preparations of single or mixed cultures of Trichoderma species, in particular T. harzianum, and T. koningii, are registered as biocontrol agents for soil and plant pathogens. In this context, it is emphasized that the four mycotoxin-producing species of the recently established Brevicompactum clade (T. brevicompactum, T. arundinaceum, T. turrialbense, and T. protrudens) are not closely related to any of the Trichoderma species currently used as biocontrol agents. Furthermore, possible health concerns about release of peptaibiotics in the biosphere are discussed with respect to their bioactivities and their use as drugs in human and veterinary medicine. Finally, future prospects regarding novel bioactivities and further research needs, including interdisciplinary taxonomic approaches, are outlined.