Ultrastructural Studies on Thermomyces lanuginosa and Certain Other Closely Related Thermophilic Fungi

Abstract

SUMMARYFine structural details of the thermophiles Thermomyces lanuginosa, T. stellatus, Humicola insolans, and H. grisea var. thermoidea are described and illustrated. When grown at elevated temperatures, these thermophiles were observed to contain from one to several large, membrane-bound inclusion bodies in the cytoplasm. These inclusion bodies were usually seen in close association with a rich detail of membranes that appeared continuous with the plasma membrane. The electron opacity of these intracytoplasmic inclusion bodies was enhanced markedly by treatment of the hyphae with the osmiophilic reagent thiocarbohydrazide, but not with alkaline diaminobenzidine-hydrogen peroxide. The known cytochemical reactions of thiocarbohydrazide with cellular lipid components suggested that these inclusion bodies might be lipoidal in nature, and that they might represent an organelle related in some manner with the thermophilic nature of these fungi. Similar intracytoplasmic inclusion bodies could not be demonstrated in hyphae of the thermophiles Chaetomium thermophile var. coprophile, Mucor pusillus, or Thermoascus aurantiacus.