8 – Ambient- and Low-Temperature Scanning Electron Microscopy

Inhibition of plant pathogenic fungi by endophytic Trichoderma spp. through mycoparasitism and volatile organic compounds.

Morphological variation was examined in 19 strains of Aspergillus fumigatus Fres. isolated from the sputum of five patients with aspergilloma. For each patient a series of variant strains was obtained which exhibited gross differences in growth rate, colour and texture of the colony. On microscopical examination, some of the strains were found to produce markedly abnormal fruiting heads which were uncharacteristic for the species. Scanning electron microscopy revealed that the variant produced conidia of anomalous size, shape and surface-sculpturing. The significance of the isolation of morphological variants of A. fumigatus in sputum and their selection in vivo are discussed.

Morphological studies on clinical isolates of Aspergillus fumigatus

SUMMARY Cultural features and morphology of 11 isolates of the hyphomycete Hirsutella thompsonii, an important pathogen of various eriophyoid mites, are described and illustrated. Three morphologically distinct groups of H. thompsonii were distinguished and accordingly three varieties are proposed: H. thompsonii var. thompsonii, var. vinacea and var. synnematosa. The variety vinacea is characterized by vinaceous colonies and a different host, Acalitus vaccinii. The strains accommodated in the var. synnematosa were isolated from Eriophyes spp. and related genera. In fresh culture they produce cream-colored cylindrical synnemata, bearing two kinds of phialides: (1) single phialides with solitary conidia and (2) densely crowded phialides with catenulate conidia. In all three varieties two different conidiogenous structures are formed: (1) solitary often proliferating phialides producing one or more globose, verrucose conidia and (2) polyblastic conidiogenous cells with smooth-walled, subglobose to ellipsoidal conidia. Although H. thompsonii differs in some morphological characters from other species in the genus, its maintenance in Hirsutella is proposed.

Taxonomy of the Acarine Parasite Hirsutella Thompsonii

A hyphomycetous fungus isolated from montane fen soil in the Caucasus Mountains, Russia, had obscurely sympodial conidiogenous cells that suggested a link to the heterogeneous genus Leptodontidium. Sequence analysis of the nuclear ribosomal small subunit and internal transcribed spacer region, however, disclosed that the fungus was an anamorphic member of a clade containing the cleistothecial ascomycetous genus Pseudeurotium. Teberdinia, gen. nov., is proposed for the blastic, generally sympodially proliferating anamorphs in this group, and Teberdinia hygrophila, sp. nov., is proposed for the species from upland fens. Binomials are not proposed for the remaining Teberdinia anamorphs of Pseudeurotium species. Purely anamorphic isolates in this clade are difficult to recognize using current morphological keys and might be more widely distributed and ecologically significant than is currently evident.

The hyphomycete Teberdinia hygrophila gen. nov., sp. nov. and related anamorphs of Pseudeurotium species

A simplified technique to prepare fungal specimens for scanning electron microscopy is described and discussed. Fixation in either 6% glutaraldehyde or 2% Os04 (both unbuffered aqueous solutions), yielded good results. The minimum fixation time in OSO4 was 2 h, in glutaraldehyde 4 to 5 h. Chemical dehydration with 2-methoxyethanol or 2,2-dimethoxypropane proved to be useful since it considerably reduced the preparation time. Because of the relatively few changes of reagent solutions during the whole process, the fungal specimens were less disturbed without much loss of material. The preparation technique described has been applied to specimens of various fungal groups with good results.

Stalpers Ja

Papers

A simplified technique to prepare fungal specimens for scanning electron microscopy.