Immunogold–silver staining of extracellular ligninases secreted by Phanerochaete chrysosporium

The secretion of ligninases by Phanerochaete chrysosporium was investigated with polyclonal antibodies, followed by immunogold–silver staining and light microscopy. After growing fungal mycelium on nitrocellulose, extracellular ligninases were detected around old, plasmaless hyphae, but not at arthrospores, chlamydospores, or blastoconidia. Labeling of fungal hyphae on cover-slip cultures was observed only when the cell wall was highly porous and translocation of cell material occurred. These experiments suggested that there is a correlation between hyphal lysis and the release of extracellular ligninases from hyphae. Key words: ligninase secretion, immunogold–silver staining, Phanerochaete chrysosporium.

Antifungal activity in culture filtrates of the ectomycorrhizal fungus Pisolithus tinctorius

The ectomycorrhizal fungus Pisolithus tinctorius secreted a metabolite that lysed hypha and conidia and inhibited the germination of conidia in a range of phytopathogenic fungi. The optimum incubation period for the production of the metabolite by P. tinctorius in liquid culture was 42–56 days. Dilutions of the culture filtrate with fresh medium caused a gradient of inhibitory effects. For hyphal lysis the minimum ratio of culture filtrate to medium for complete growth inhibition was 5:1 for Rhizoctonia praticola and Truncatella hartigii and 3:1 for Sphaerosporella brunnea. At higher dilutions, the hyphae that formed were short celled and highly branched; many hyphae lysed. Conidial germination was completely inhibited at a ratio of 5:1 for both Fusarium solani and T. hartigii, 3:1 for a North American isolate of Brunchorstia pinea (NA), 1:1 for a European isolate of B. pinea (EU), and 1:3 for two strains of Cochliobolus sativus (0910, 0912). Conidial lysis was seen for T. hartigii at a ratio of 5:1 and at a ratio of 1:1 for B. pinea (EU) and C. sativus (0910). Characterization of the cell-free culture filtrate through the separate additions of D-glucose and an adsorbent, activated charcoal, showed that hyphal lysis and conidia germination inhibition did not result from a depletion of carbohydrates from the growth medium but from the presence of some substance adsorbed by charcoal. Key words: Pisolithus tinctorius, allelopathy, antifungal metabolite, hyphal lysis, mycorrhizosphere.

Thallphytic Alleopathy: Isolation and Identification of Laetisaric Acid

Laetisaria arvalis, a soil-dwelling basidiomycete fungus, secretes an allelopathic agent that induces rapid hyphal lysis in several phytopathogenic fungi. The active compound was isolated from chloroform:methanol extracts ofL. arvalismycelia and characterized as a previously unknown hydroxy fatty acid, (Z,Z-9,12-8-hydroxyoctadecadienoic acid.