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Biomedical subjects

Heidrun Anke

Publications and source records attributed to Heidrun Anke.

14 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

Characterization of the ferrichrome A biosynthetic gene cluster in the homobasidiomycete Omphalotus olearius.

Under iron deprivation Omphalotus olearius was found to produce the hydroxamate siderophore ferrichrome A. A gene cluster consisting of three genes: fso1, a nonribosomal peptide synthetase whose expression is enhanced in the absence of iron; omo1, a l-ornithine-N(5)-monooxygenase; and ato1, an acyltransferase probably involved in the transfer of the methylglutaconyl residue to N(5)-hydroxyorinithine was identified. The fso1 sequence is interrupted by 48 introns and its derived protein sequence has a similar structure to the homologous genes of Ustilago maydis and Aspergillus nidulans. This is the first report of a nonribosomal peptide synthetase gene and a biosynthetic gene cluster in homobasidiomycetes.

Acyltransferases↗
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↗
PubMed2005

Heptemerones A-G, seven novel diterpenoids from Coprinus heptemerus: producing organism, fermentation, isolation and biological activities.

Seven novel diterpenoids, named heptemerones A-G, were isolated from the broth of submerged cultures of Coprinus heptemerus, a basidiomycete which previously had not been known to produce secondary metabolites. The compounds were purified by solid phase extraction and silica gel chromatography followed by preparative HPLC. Among the biological activities the inhibition of fungal germination was the most potent, and depended highly on the composition of the assay medium. In water, inhibition occurred at 5 - 10 fold lower concentrations as compared to complex media. Heptemerone G was the most active compound with MICs starting at 1 microg/ml. Four of the antifungal compounds exhibited plant protective activity in a leaf segment assay using Magnaporthe grisea as the pathogen. Growth of yeasts and bacteria was hardly affected. Cytotoxic activities were moderate and only heptemerone D was phytotoxic.

Antibiotics, Antineoplastic↗
PubMed2005

Favolon B, a new triterpenoid isolated from the Chilean Mycena sp. strain 96180.

A new biologically active triterpenoid, favolon B (1), was isolated from fermentation broths of Mycena sp. strain 96180. Favolon B showed antifungal activities towards Botrytis cinerea, Mucor miehei, Paecilomyces variotii and Penicillium notatum. No activities were observed against bacteria and yeasts. The structure of favolon B was elucidated by spectroscopic techniques.

Antifungal Agents↗
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

New peptaibols from Mycogone cervina.

From cultures of Mycogone cervina, a mycophilic fungus growing on the fruit bodies of ascomycete Paxina acetabulum, two new peptaibols (cervinin, N-Ac-Leu-Aib-Pro-Aib-Leu-Aib-Pro-Ala-Aib-Pro-Val-red-Leu (1) and the red-Leu O-acetylated derivative 2) were isolated. The structures of 1 and 2 were elucidated by spectroscopic techniques. They exhibited weak antibacterial as well as cytotoxic activities. They are the first secondary metabolites described from M. cervina.

Animals↗
PubMed2002

Hericenols A-D and a chromanone from submerged cultures of a Stereum species.

Extracts of submerged cultures of a Stereum species afforded four new pentasubstituted phenolic compounds, named hericenols A, B, C, and D (1-4), 6-hydroxymethyl-2,2-dimethylchroman-4-one (5) and the known erinapyrone C. Hericenol A (1) showed weak antimicrobial activity while hericenol C (3) was weakly cytotoxic. The structures of the metabolites were determined by spectroscopic techniques.

Animals↗
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↗
PubMed2002

Biologically active secondary metabolites from the ascomycete A111-95. 1. Production, isolation and biological activities.

Eight secondary metabolites were isolated from submerged cultures of the ascomycete A111-95 during a search for new nematicidal metabolites. (-)-Galiellalactone (7) and compound 2 are metabolites previously obtained from cultures of Galiella rufa while the compounds 1, 3, 4, 5, 6 and 8 (3 and 4 were obtained as an unseparable mixture), were isolated as natural products for the first time. Compound 2, pregaliellalactone (5) and the mixture of 3 and 4 showed nematicidal activities towards Caenorhabditis elegans and Meloidogyne incognita. All compounds showed moderate or weak cytotoxic activities.

Animals↗
PubMedDate not supplied

Siderophores produced by Magnaporthe grisea in the presence and absence of iron.

An analysis of siderophores produced by Magnaporthe grisea revealed the presence of one intracellular storage siderophore, ferricrocin, and four coprogen derivatives secreted into the medium under iron depletion. Structural analysis showed that the compounds are coprogen, coprogen B, 2-N-methylcoprogen and 2-N-methylcoprogen B. Siderophore production under low and high iron conditions was quantified.

Gas Chromatography-Mass Spectrometry↗