Secondary Fungal Metabolites and Their Biological Activities, II. Occurrance of Antibiotic Compounds in Culturesof Armillaria ostoyaeGrowing in the Presence of an Antagonistic Fungus or Host Plant Cells

Abstract

We found that in the presence of host plant cells or some antagonistic fungi, the highly forest-pathogenic basidiomycete Awn7/0n'o ostoyae is strongly stimulated to produce a series of toxic secondary metabolites which are capable of inhibiting the growth of the antagonist or of killing the plant cells still before cell contact. The chemical structures of the metabolites have been identified, of which two of them are new compounds. The time dependence and sites of synthesis in the mycelium have been determined in order to lay the foundation for future studies concerning the induction mechanism for the synthesis of the toxins. Sekundäre Püzmetabolite und ihre biologische Aktivität, II. Vorkommen antibiotischer Verbindungen in Kulturen von Armillaria ostoyae, die in Gegenwart von antagonistischen Pilzen oder von Pflanzenzellen gebildet werdenZusammenfassung: Wir fanden, daß in dem stark pathogenen Basidiomyceten Armillaria ostoyae bereits vor der Infektion einer Wirtspflanze, aber auch in Gegenwart antagonistischer Pilze die Synthese einer Reihe toxischer Sekundärmetabolite stark stimuliert wird. Unter diesen Metaboliten wurden zwei neue Verbindungen identifiziert. Der Mechanismus der Induktion der Toxinsynthesen ist unbekannt. Um für diesbezügliche künftige Arbeiten die notwendigen Grundlagen zu schaffen, wurde der Zeitverlauf ihrer Bildung gemessen und die Bereiche im Mycel lokalisiert, in denen die Toxine vermehrt gebildet werden.

In vitro interaction studies between Glomus intraradices and Armillaria mellea in vines

“…Hepper (1979) observed that the spore germination and the growth of AM fungal mycelium could be stimulated or inhibited by different compounds, and the production of toxic secondary metabolites by Armillaria sp. has been reported by several authors (Peipp and Sonnenbichler, 1992;Sonnenbichler et al, 1994). The release of these compounds, induced by the presence of antagonistic fungi and plant cells, can inhibit the growth of other microorganisms and even induce cell death before any contact occurs (Peipp and Sonnenbichler, 1992).…”

“…has been reported by several authors (Peipp and Sonnenbichler, 1992;Sonnenbichler et al, 1994). The release of these compounds, induced by the presence of antagonistic fungi and plant cells, can inhibit the growth of other microorganisms and even induce cell death before any contact occurs (Peipp and Sonnenbichler, 1992). Soluble or volatile compounds produced by the pathogenic fungus could therefore have inhibited the sporulation and the development of the extraradical mycelium of G. intraradices.…”

Sesquiterpene aryl ester natural products in North American Armillaria species

“…No data exist as to which melleolide concentration occurs in the wood or the rhizosphere, where close organismal interactions between Armillaria and other microorganisms take place. However, given the observation that (1) cocultivation with competitors can increase melleolide titers (Peipp and Sonnenbichler 1992), that (2) the melleolides are recovered from the broth, but only in traces from fruiting bodies or the ground up biomass, and that (3) titers in the broth typically reach concentrations sufficient for inhibition during in vitro assays (>5 mg/l), a role for melleolides in inhibitory microbial communication appears plausible. Primary targets seem wood-rotting basidiomycetes as potential competitors which populate the same habitat, but at least to some degree other ubiquitous microbes as well, such as Streptomycetes and Penicilli.…”

“…Intriguingly, coupling of these two building blocks via esterification is a unique biosynthetic capacity of the genus Armillaria. Antimicrobial activity was reported for some of the 51 published aryl esters (Donnelly et al 1982;Arnone et al 1986;Momose et al 2000), and a role for intra-and interspecific communication was proposed (Peipp and Sonnenbichler 1992;Sonnenbichler et al 1994;Sonnenbichler et al 1997). Only very sporadically has data on Armillaria natural products been coupled to information on the geographic origin of the fungal strains.…”

A Fivefold Parallelized Biosynthetic Process Secures Chlorination of Armillaria mellea (Honey Mushroom) Toxins

“…The melleolides are intriguing, as they show two distinct structure-activity relationships for their cytotoxic and antifungal bioactivities (8). Phytotoxic activities have also been established (9,10). Further, the melleolides represent one of the largest fungal natural product families with more than 60 structural variants.…”