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Abstract

A rapid progress made for ultrathin sectioning technique in electron microscopy has contributed much to the analysis of microbial cell structures. Recently, several papers (3,(7)(8)(9)17,18,23) have appeared on the subject of electron microscopic studies of certain dermatophytes, and the structural details of fungal cells have been exposed to some extent through electron microscopy of ultrathin sections. However, the published electron micrographs of the organism, especially those in its early stage, were not of sufficient quality to reveal the detail architectures of the fungus. Moreover, the findings of the cell structures hitherto obtained have not been always agreeable among workers, and many problems of the fine structures of the organism still remained to be studied.Since Watson (1958)(25,26) succeeded in enhancing the contrast and resolution in thin sections of biological materials, using stain technique with heavy metals, several modifications(4,10,16) of his method have been reported, and these electron-opaque stains have been widely applied to tissue sections for electron microscopy. Vitols, North and Linnane (1961)(24) first reported that uranyl nitrate treatment of the whole cells of Saccharomyces cerevisiae after permanganate fixation leads to better preservation of the membrane structures and also to an improvement in general contrast. This paper describes some of the fine structures of Trichophyton mentagrophytes as observed chiefly by staining the thin sections of fungus cells with various heavy metals. MATERIALS AND METHODSOrganism employed: A stock culture of Trichophyton mentagrophytes, strain J-812, maintained on a glucose peptone agar at 27 C, was used. This strain was obtained from Dr. T. Tsuchiya, Professor of Juntendo University School of Medicine.Culture media employed: The medium mostly used was a glucose (1 per cent) peptone (1 per cent) water adjusted to pH 5.6.Electron microscopy of thin sections : Hyphal pellets of the strain grown on the medium for 5 to 7 days at 27 C were harvested by centrifugation and washed with sterile veronal-acetate buffer solution several times. These pellets of about 1 to 2 mm in diameter were fixed in 1 per cent osmium tetroxide solution, or 2 per cent potassium permanganate buffered at pH 6.99 with veronal-acetate buffer, for 24 hr at 4 C.