Modes of cell-wall degradation of Sphagnum fuscum by Acremonium cf. curvulum and Oidiodendron maius

Electron microscopy of cryo-fractured hyaline leaf cells of Sphagnum fuscum Klinggr. revealed that their cell walls consist of three layers: a thick c entral layer flanked on either side by a thinner, amorphous layer. Acremoni um cf. curvulum W. Gams and Oidiodendron maius Barron, both isolated from p artly decomposed S. fuscum plants, were capable of degrading leaf cell wall s of Sphagnum. Where hyphae of A. curvulum accumulated, the amorphous, oute r wall layer of S. fuscum was first fragmented and then removed. The expose d central wall layer consisted of bundles of microfibrils embedded in an am orphous matrix material. After the matrix material and the inner surface wa ll layer were mostly removed, degradation of microfibrils occurred and loca lized voids were produced. Unlike A. cf. curvulum, O. maius degraded all wa ll components more or less simultaneously. In both fungi, active and autoly sing hyphae frequently occurred in proximity on the Sphagnum leaves.