Biomedical subjects

Tom Gräfenhan

Publications and source records attributed to Tom Gräfenhan.

4 recordsLinked to original sources

PubMed2006

Trichoderma brevicompactum complex: Rich source of novel and recurrent plant-protective polypeptide antibiotics (peptaibiotics).

Three strains of Trichoderma brevicompactum and another four that are closely related to that species (Trichoderma cf. brevicompactum) were analyzed for the formation of polypeptide antibiotics (peptaibiotics) by LC/ESI-MS(n). These isolates were selected because of an antagonistic potential against Eutypa dieback and Esca disease of grapevine and have not yet been investigated for the production of peptide antibiotics. Fully grown cultures on potato dextrose agar were extracted with CH2Cl2/MeOH, and this extract was subjected to SPE using C18 cartridges. The methanolic eluates were analyzed by LC/ESI-MS(n). All strains were found to produce membrane-active alamethicins F30. In addition to that, novel peptaibiotics were detected, namely, 14 12-residue trichocryptins B, 12 11-residue trichocryptins A, 19 11-residue trichobrevins A and B, 6 10-residue trichoferins, and 17 8-residue trichocompactins. These compounds may partially be responsible for the plant-protective action of the producers. Chemotaxonomic considerations also indicated the necessity to introduce another new species that is closely related to T. brevicompactum.

Anti-Bacterial Agents↗

PubMed2006

Peptaibiomics: Screening for polypeptide antibiotics (peptaibiotics) from plant-protective Trichoderma species.

Eight strains of Trichoderma species (T. strigosum, T. erinaceus, T. pubescens, T. stromaticum, and T. spirale as well as T. cf. strigosum, T. cf. pubescens) were selected because of their antagonistic potential against Eutypa dieback and Esca which are fungal diseases of grapevine trunks. These isolates were screened for the production of a group of polypeptide antibiotics named peptaibiotics, including its subgroups peptaibols and lipopeptaibols. Fully-grown fungal cultures on potato-dextrose agar were extracted with CH(2)Cl(2)/MeOH, and these extracts were subjected to SPE using C(18) cartridges. The methanolic eluates were analyzed by on-line LC/ESI-MS(n) coupling--a method which is referred to as 'peptaibiomics'. New seven-, ten-, and eleven-residue lipopeptaibols, with N-terminal alkanoyl, and C-terminal leucinol or isoleucinol residues were found and named lipostrigocins and lipopubescins. Furthermore, new 18-residue peptaibols named trichostromaticins and 19-residue peptaibols named trichostrigocins were discovered. One peptaibiotic carrying a free C-terminal valine (or isovaline) named trichocompactin XII was also sequenced. These results corroborate the hypothesis that peptaibiotics might contribute to the plant-protective action of their fungal producers. The data also point out that comparison of peptaibiotic sequences is of limited relevance in order to establish chemotaxonomic relationships among species of the genus Trichoderma.

Anti-Bacterial Agents↗

PubMed2005

Trichothecene production by Trichoderma brevicompactum.

Trichoderma brevicompactum, T. viride, T. harzianum, T. atroviride, T. longibrachiatum, T. erinaceum, T. citrinoviride, and Hypocrea lutea were screened for production of trichothecenes after growth on one or several solid and liquid media. Trichothecenes were detected by liquid chromatography combined with online UV/vis spectroscopy and electrospray high-resolution mass spectrometry. T. brevicompactum produced trichodermin and/or harzianum A on all media investigated, with liquid media yielding the largest amounts. Detection of octa-2Z,4E,6E-trienedioic acid in the harzianum-A-producing strains indicated that harzianum A was synthesized directly by esterification of trichodermol with octa-2Z,4E,6E-trienedioic acid. Both the T. viride strain from which trichodermin was originally isolated and the T. harzianum strain from which harzianum A was originally isolated were shown to belong to T. brevicompactum based on four independent criteria: metabolite profiles, micromorphology, macromorphology on yeast extract sucrose agar and potato dextrose agar, and DNA sequences of the ITS1/ITS2 regions of the nuclear ribosomal DNA.

Chromatography, Liquid↗

PubMed2005

A re-evaluation of Lulworthiales: relationships based on 18S and 28S rDNA.

The Lulworthiales consists of four genera: three that were removed from the Halosphaeriales, namely Lulworthia, Lindra, and Kohlmeyeriella; and Spathulospora, reassigned from the Spathulosporales. However, studies have shown that neither Lulworthia nor Lindra are monophyletic genera. This study was therefore undertaken to re-evaluate the genera of the Lulworthiales based on the SSU and LSU rDNA genes. Taxonomic revisions are proposed here for Lulworthia crassa, L. lignoarenaria, L. uniseptata and Lindra marinera: Lulworthia crassa is transferred into the genus Kohlmeyeriella; Lulwoidea gen. nov. is established for L. lignoarenaria; Lulwoana gen. nov. is established for L. uniseptata; and Lindra marinera is reduced to synonymy with L. thalassiae. Taxonomic descriptions are emended for the genus Lulworthia s. str., and for L. grandispora and Lindra thalassiae. A neotype is designated for Lulworthia grandispora.

Ascomycota↗