[Ultrastructural study of the biodegradation processes. I. Beech (Fagus sylvaticus L.) leaf white rot]. / Etude ultrastructurale des processus de biodégradation. I. Pourriture blanche des feuilles de Hêtre (Fagus sylvatica L.).

An electron microscopic study of beech leaf white rot shows a certain number of characteristic developmental stages which are identical whether the material is from in vitro experimentation or from natural incubation. Endowed with a cellulolytic properly seemingly localized in the apical region only, hyphae of the white rot agent only traverse the plant cell walls. Subsequently, hyphae penetrate condensed protoplasmic residues and make them progressively transparent to electrons. During this discoloring process, a lethal factor of as yet unknown nature appears, affecting other microorganisms already present in the leaves. Phloem and xylem vascular bundles do not present notable ultrastructural modifications. Therefore, leaf discoloration is not due to an alteration of the xylem constituents but to changes having occurred in the condensed cytoplasmic residues of the dead tissues.

[Influence of clay on microorganisms conservation. I. Ultrastructural study of the biodegradation of Beauveria bassiana (Bals). Vuill. (entomopathogenous hyphomycete) in soil (author's transl)]. / Effet de l'argile sur la conservation des microorganismes. I. Etude ultrastructurale de la biodégradation dans le sol de l'hypomycète entomopathogène Beauveria bassiana (Bals.) Vuill.

Blastospores of B. bassiana enclosed in fine mesh bags were submitted to soil microflora. Clay minerals coating fungal spores protected from by decreasing bacterial activity. The role of amoeba in biodegradation of fungi is also considered.

[Biodegradation of the mycelium of Pyrenochaeta lycopersici Schneider et Gerlach in the soil. Ultrastructural study]. / Biodegradation du mycelium de Pyrenochaeta lycopersici Schneider et Gerlach dans le sol. Etude ultrastructurale.

Under natural conditions, Pyrenochaeta lycopersici forms a sterile mycelium. Some strains form chlamydospores, while others form micro-sclerotia. The fungus survives by hyphae cells which are present in soil either free-living or momentarily protected by the tissue of the infected root. In a model experiment, the behaviour of the free mycelium was tested in a soil which had been supplied with asparagine and manure, respectively. A known quantity of living mycelium was added to the prepared soils. Samples were taken after 1, 3, 6, and 10 months. They were examined on loss of weight of the mycelium, inoculum potential, and ultra-structure of the hyphae before and during degradation by transmission electron microscopy.

[Study of the Rhodotorula rubra cell wall. VII Influence of chloramphenicol on its morphology and phosphatase activity (author's transl)]. / Etude des parois de Rhodotorula rubra: VII. Influence du chloramphenicol sur la morphologie et les phosphatses des parois de Rh. rubra

Rh. rubra grown in the presence of chloramphenicol (500 mug/ml of medium) displayed morphological and biological changes, including formation of aberrant mitochondria with altered cristae, increase of the ratio fundamental element/mucilaginous sheath and electron-transparent regions in the cell walls. After treatment of the yeast with trypsin or beta-glucanase complex, acid and alkaline phosphatases remained localised within the cell wall, but the effect of the degradative enzymes on the activity of the phosphatses differed in cells grown in the presence of chloramphenicol and those grown without the antibiotic. The data suggest that chloramphenicol induced either structural fragility or increased permeability of the cell walls.

[Effect of ethylene diamine on cell wall of three yeasts of the genus Rhodotorula]. / Incidence du traitement par l'éthylène diamine sur l'ultrastructure des parois de trois levures du genre Rhodotorula

The treatment of ethylene diamine of Rhodotorula yeast cells does not alter the fibrillar structure of their wall basic frame. Dissolved substances constitute the external mucilaginous layer and elements intimately incrusted in the wall.