Biomedical subjects
Publications and source records attributed to F Mangenot.
Variations between seasonal samplings of a forest soil were studied during a one year cycle. The total number of microorganisms was maximal in march, while qualitative variations of the bacterial and fungal flora were unimportant. Electron microscope studies showed physiological differences and enabled to evaluate the seasonal variations of the type of associations of soil microbes.
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.
The activity range of an enzymatic preparation from Myxococcus xanthus was assayed against some soil and rhizospheric bacteria. The lysis of unequally aged sensitive eubacterial populations, as related to their viability, was investigated and, at last, the often used streak method was checked and the relationship between cell viability and susceptibility to lysis is discussed.
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