Biomedical subjects

Roland W S Weber

Publications and source records attributed to Roland W S Weber.

12 recordsLinked to original sources

PubMed2006

Antiamoebins, myrocin B and the basis of antifungal antibiosis in the coprophilous fungus Stilbella erythrocephala (syn. S. fimetaria).

Antiamoebins I, III and XVI as well as several others in minor amounts were produced by four strains of the coprophilous fungus Stilbella erythrocephala (syn. S. fimetaria) in its natural substrate and in liquid culture. The total antiamoebin concentration in dung was 126-624 microg g(-1) fresh weight, with minimum inhibitory concentrations against most other coprophilous fungi being at or below 100 microg mL(-1). Myrocin B, not previously described from S. erythrocephala, was also produced, but only at low, nonfungicidal levels (< 5.3 microg g(-1)). No other antifungal substances were detected. It is concluded that antiamoebins are responsible for antibiosis in dung colonized by S. erythrocephala.

Antibiosis↗

PubMed2005

Biosynthesis of the xanthophyll plectaniaxanthin as a stress response in the red yeast Dioszegia (Tremellales, Heterobasidiomycetes, Fungi).

Carotenoid biosynthesis was examined in a phylloplane yeast identified by ITS, 18S and 28S rDNA analysis as a Dioszegia sp. close to D. takashimae. In well-aerated flask or fermentor cultures, this strain produced essentially a single pigment confirmed as the xanthophyll plectaniaxanthin by NMR analysis, at concentrations of 103-175 microgg(-1) biomass dry weight. Detailed studies showed increases in plectaniaxanthin concentrations in the presence of 5 mM hydrogen peroxide (1.8-fold), 50 and 100 microM duroquinone (3.1- and 3.7-fold, respectively), and 2% ethanol (4.9-fold). Whereas oxidative stress is known to enhance the biosynthesis of torularhodin or astaxanthin in other red yeasts where they are associated with an antioxidant function, this is the first report implicating plectaniaxanthin in a similar role. At reduced aeration, biosynthesis of plectaniaxanthin was suppressed and its putative precursor gamma-carotene accumulated. The carotenoid cyclase inhibitor nicotine (5-20 mM) inhibited plectaniaxanthin formation, with lycopene accumulating stoichiometrically. Hydroxy groups at C-1' and C-2' therefore seem to be introduced late in plectaniaxanthin biosynthesis, following cyclization of the beta-ionone ring.

Cell Count↗

PubMed2005

Laetiporic acids, a family of non-carotenoid polyene pigments from fruit-bodies and liquid cultures of Laetiporus sulphureus (Polyporales, Fungi).

The non-isoprenoid polyene laetiporic acid A, recently described from fruit-bodies of the wood-rotting fungus Laetiporus sulphureus, was found to be the major orange pigment also in mycelium grown in liquid culture. Its formation was variable, ranging from 0.1 to 6.7 mg/g dry weight in three strains, all of which were identified as L. sulphureus by ITS rDNA sequence analysis. A second pigment, 2-dehydro-3-deoxylaetiporic acid A, is also described and fully characterized by NMR spectroscopy. Two further minor pigments, laetiporic acids B and C, were produced in liquid culture. These resemble laetiporic acid A but are enlarged by two and four carbon atoms, respectively, resulting in chromophores with 11 or 12 instead of 10 conjugated double bonds as described for laetiporic acid A. Since fruit-bodies of L. sulphureus are edible, laetiporic acids might hold potential as food colourants.

Molecular Structure↗

PubMed2005

Production of sordarin and related metabolites by the coprophilous fungus Podospora pleiospora in submerged culture and in its natural substrate.

Rabbit pellets collected from the field were colonized by Podospora pleiospora at the exclusion of other coprophilous fungi, suggesting antibiosis. In liquid culture, P. pleiospora produced sordarin (1); sordarin B (2), a new compound in which sordarose is replaced by rhamnose; hydroxysordarin (3); and sordaricin (4). The major compounds 1 and 2 exhibited minimum inhibitory concentrations of 0.5-2.5 microg ml(-1) against the yeasts Nematospora coryli and Sporobolomyces roseus, but showed little or no activity against bacteria or coprophilous filamentous fungi. In liquid culture, the production of 1 and 2 together amounted to 2.7 microg ml(-1), whereas in rabbit dung only 1 was produced at a similar concentration (2.3 microg g(-1) fresh weight). The biosynthesis of these substances was unaffected by the presence of inoculum of other fungi tested (Sporobolomyces roseus or Penicillium claviforme) in liquid culture or on dung. Sordarin-type natural products are therefore synthesized by P. pleiospora at sufficiently high concentrations to account for antibiosis against yeasts, but not against filamentous fungi.

Animals↗

PubMed2004

3-hydroxypropionic acid as a nematicidal principle in endophytic fungi.

3- Hydroxypropionic acid was isolated by bioactivity-guided fractionation of extracts obtained from submerged cultures of several endophytic fungi isolated from above-ground plant organs. This compound showed selective nematicidal activity against the plant-parasitic nematode Meloidogyne incognita with LD50 values of 12.5-15 microg/ml. Activity against the saprophytic Caenorhabditis elegans was fivefold lower. No antimicrobial, cytotoxic or phytotoxic effects were observed. Propionic acid and D- and L-lactic acids were not active against either nematode species. Based on morphological features and ITS, 18S and 28S rDNA analyses, the producing strains were identified as Phomopsis phaseoli isolated from the leaf of a tropical tree, and four strains of Melanconium betulinum isolated from twigs of Betula pendula and B. pubescens in Germany. This is the first report of 3-hydroxypropionic acid in fungi, and of the nematicidal activity of this metabolite.

Animals↗

PubMed2004

Fungal secondary metabolites as inhibitors of infection-related morphogenesis in phytopathogenic fungi.

The life-cycle of many plant-pathogenic fungi, especially those infecting aerial plant organs, contains several specific developmental stages. If these are sufficiently distinct in their physiology from vegetative hyphal growth, they present potential targets for non-fungitoxic plant protectants. The present review identifies such targets especially in the pre-penetration stages of the infection cycle of Magnaporthe grisea and other fungi infecting from air-borne spores. Examples of non-toxic natural products with activity against spore germination, attachment, appressorium formation, appressorium maturation and penetration of the host surface are given. In contrast, no substances selectively active against in planta growth or sporulation appear to be known. The selective activity of numerous secondary metabolites against specific infection stages without accompanying toxicity against vegetatively growing hyphae indicates a direction for the development of future natural product-derived fungicides which are more easily degraded in the environment and possess fewer non-target effects. Such substances are produced by many saprotrophic and endophytic fungi in pure culture. The paucity of data on the production of biologically active substances in natural situations limits the interpretation of their ecophysiological significance for the producer.

Antifungal Agents↗

PubMed2004

Brefeldin A production by Phoma medicaginis in dead pre-colonized plant tissue: a strategy for habitat conquest?

Phoma medicaginis was isolated as the dominant endophyte from surface-sterilized shoots of Medicago sativa and M. lupulina growing outdoors. Plants were either symptomless or showed signs of infection in the shape of limited lesions which sometimes contained melanized pycnidial initials. Rapid colonization of host tissue and sporulation were observed within 9 d on dead plant material upon incubation in a moist chamber. Such colonized material, but not freshly harvested living tissue, contained brefeldin A (1.7 microg g(-1) D.W.). This toxin was also produced in pure culture (20 mg l(-1)) and in artificially inoculated autoclaved M. sativa stems (3 mg g(-1) D.W. =920 microg ml(-1)). The latter concentration of brefeldin A should be similar to that produced within a fruiting lesion of P. medicaginis and suppressed spore germination and growth of nine of 11 common phylloplane fungi tested. This metabolite may thus have a function in substrate defence after the switch from the endophytic to the saprotrophic period in the life-cycle of P. medicaginis following the death of infected host tissue.

Ascomycota↗

PubMed2003

Phylogenetic analysis of Puccinia distincta and P. lagenophorae, two closely related rust fungi causing epidemics on Asteraceae in Europe.

Phylogenetic analyses of the ITS1-5.8S-ITS2 region of the ribosomal RNA gene cluster were carried out with two short-cycled (aecial/telial) European rusts on Asteraceae, Puccinia distincta causing the current pan-European epidemic on Bellis perennis, and P. lagenophorae causing a similar disease on Senecio spp., as well as the macrocyclic P. obscura which alternates between B. perennis (pycnial and aecial host) and Luzula spp. (main host). All three species formed a well-resolved cluster when compared with the ITS sequences of a range of other rust fungi, using both parsimony and distance methods. The sequences of P. distincta and P. lagenophorae differed from each other at three positions whereas P. obscura differed from P. distincta at 37 points. Together with consistent morphological and epidemiological differences across Europe, these data support the recognition of P. distincta as a separate species from P. lagenophorae. Both may be derived from P. obscura, although the precise evolutionary history remains obscure.

Asteraceae↗

PubMed2002

Simple method for reversed-phase high-performance liquid chromatographic analysis of fungal pigments in fruit-bodies of Boletales (Fungi).

A reversed-phase HPLC method has been developed for the analysis of hydroxylated pulvinic acid derivatives which are responsible for the pigmentation of fruit-bodies belonging to the order Boletales (Fungi). Variegatic, xerocomic and atromentic acid as well as variegatorubin were detected and separated in methanolic extracts of Boletus permagnificus and Xerocomus parasiticus, and the pigment profile of these species was compared. The identity of the pigments was confirmed by means of LC-atmospheric pressure chemical ionization (APCI) mass spectrometry.

Basidiomycota↗

PubMed2002

Identification and quantification of carotenoid pigments in aeciospores of the daisy rust fungus, Puccinia distincta.

The yellow-orange colour of aeciospores of the daisy rust fungus, Puccinia distincta, was found to be due to the carotenoid pigments beta,psi-carotene (gamma-carotene) and beta,beta-carotene (beta-carotene), which were identified by means of HPLC-APCI-MS. The combined concentration of beta- and gamma-carotene in the aeciospores was 3.3x10(-15) mol spore(-1) or 6 mol% mol(-1) total fatty acids. This concentration is sufficient for a postulated antioxidant role of carotenoids as free radical scavengers.

Basidiomycota↗

PubMed2002

Galiellalactone and its biogenetic precursors as chemotaxonomic markers of the Sarcosomataceae (Ascomycota).

(-)-Galiellalactone is a hexaketide metabolite with interesting pharmacological activities which was detected in four strains of Galiella rufa (Sarcosomataceae, Ascomycota) and in two unidentified fungi shown by their 18S rDNA sequences also to belong to the Sarcosomataceae. These were a wood-inhabiting apothecial species from Chile and an endophytic isolate from Cistus salviifolius (Sardinia). Other members of the family (Urnula helvelloides, one Strumella coryneoidea isolate) produced no galiellalactone but merely hexaketides structurally related to galiellalactone precursors, whereas a third group of species (Sarcosoma latahensis, Strumella griseola, one S. coryneoidea isolate) lacked hexaketide production altogether. Despite thorough screening programmes, galiellalactone and its precursors have not yet been found in any fungus outside the Sarcosomataceae and may thus be a chemotaxonomic marker of the family, supporting its current phylogenetic definition. Two pentaketide derivatives of the 6-pentyl-alpha-pyrone type were found in all G. rufa strains as well as in A111-95 and the hexaketide-producing S. coryneoidea isolate.

Ascomycota↗

PubMedDate not supplied

Hormonemate, a new cytotoxic and apoptosis-inducing compound from the endophytic fungus Hormonema dematioides. I. Identification of the producing strain, and isolation and biological properties of hormonemate.

In a search for new fungal compounds inducing apoptosis of the colon cancer derived cell line COLO-320, hormonemate (1) was purified from fermentations of an endophytic fungus isolated from living needles of a Pinus species. The producing strain was identified as Hormonema dematioides by microscopy and ITS rDNA sequence analysis. The structure of hormonemate was determined by spectroscopic methods. The compound exhibited cytotoxic effects against the human colon tumor cell lines COLO-320, DLD-1 and HT-29 as well as five other human cell lines (HL-60, JURKAT, HEP-G2, MCF-7, HeLa S3). It also induced apoptosis in COLO-320 cells as detected by a caspase-activity assay and morphological changes, and it triggered morphological and physiological differentiation of HL-60 cells into granulocytes, which subsequently died by apoptosis.

Anti-Bacterial Agents↗