A bacteriolytic muramidase from the basidiomycete Schizophyllum commune

Abstract

___The basidiomycete Schizophyhm commune produces an extracellular bacteriolytic enzyme when grown on heatkilled cells of Bacillus subtilis as sole C , N and P source. The enzyme catalyses the dissolution of isolated B. subtilis cell walls at an optimum pH of 3.2-3-4, releasing muramyl reducing groups, which indicates that it is a muramidase. Although low levels of enzyme activity are present when the fungus is grown in the absence of bacteria, full enzyme production appears to be induced by bacterial cells and repressed by glucose. Whole bacteria are not lysed by the enzyme at pH 3.3, but are rendered osmotically fragile, and lyse when the pH is raised to 7 or higher. The muramidase is effective against several Gram-positive bacteria but did not lyse any of the Gramnegative species tested.

Hitting the Sweet Spot: Glycans as Targets of Fungal Defense Effector Proteins

“…belongs to the glycosylhydrolase family 25 (GH25) in the CAZY database (PF01183 in the PFAM database) along with homologous enzymes from other fungi, bacteria and bacteriophages. The secretome of Agaricus bisporus , which harbours four genes encoding putative GH25-type lysozymes in its genome, was shown to have lysozyme activity [82,83] but it is not clear whether the activity is due to these proteins. BLAST searches of fungal genomes with members of another family of bacterial and bacteriophage lysozymes (GH24/PF00959) suggest that fungi express representatives of at least two families of so-called microbe-type lysozymes.…”

Cytolysis of Bacillus subtilis by Fusarium oxysporum

“…At intervals, replicate flasks were harvested, as well as an uninoculated control flask, by centrifuging (5000 g, 30 min), washing the pellet once with distilled water, re-centrifuging, then freeze-drying to constant weight. The biomass of F. oxysporum grown on B. subtilis medium was estimated indirectly by extraction and measurement of the ergosterol present in the harvested material using the adaptation of the method of Seitz et al (1979) described previously (Grant et al, 1990). Cultures of F. oxysporum grown in the standard glucose medium were used to confirm that a linear relationship existed between fungal dry weight and extractable ergosterol.…”

“…Cell walls of B. subtilis 168 were prepared and wall degradation assayed as described previously (Grant et al, 1990). Reducing and amino groups were measured by the procedures of Park & Johnson (1949) and Ghuysen et al (1966) respectively.…”