Fluorescence Microscopy for the Observation
 of Nematophagous Fungi inside Soil.

by

Christian Jensen, Heike Neumeister and Gernot Lysek

Institute of Hygiene, Free University Berlin;

 Published in “Mycologist” Vol 12, Part 3, August 1998, pp 107 - 111
reproduced here with kind permission of R. T. Moore (BMS, www.bms.ac.uk).

Abstract:

Fluorochroming of soil samples makes it possible to study soil fungi in their natural habitat. This is demonstrated with some nematophagous (predacious) fungi.

Key words:

Fluorescence techniques, soil fungi, nematophagous fungi, FDA, calcofluor W

Introduction:

Fluorescence techniques have become an effective tool in microscopy. With the help of sophisticated equipment and an increasing number of fluorochromes, it is now possible to observe and differentiate a range of materials, microorganisms, electric, water or redox potentials and even living and dead cells or tissues. Most of the fluorochromes also allow the unrestricted observation of living cells.

Fluorescence microscopy has now been successfully adapted to observe soil-dwelling fungi in situ(JENSEN 1994; JENSEN & LYSEK 1991; SAXENA & LYSEK 1993).  This has been made possible by the use of specific fluorochromes such as fluorescein-di-acetate (FDA), which stains actively metabolizing cells or hyphae, and calcofluor white, which marks the hyphal walls.  Here, we present the results of the observation of soil-dwelling, predacious (mainly nematophagous) fungi.  This ecological group can in part be well characterized by the morphology of their spores (Monacrosporium or Arthrobotrys-type) and also by the presence of specific capture organs, which are often associated with the remains of captured nematodes.  To give a better overview and to allow a comparison of fluorescence and conventional microscopical images, these structures are given as schemes in fig 1. In addition fig.2 shows a scanning electron microscopic view of the typical capture organ of Arthrobotrys oligospora (Fres.), the nematophagous hyphomycete on which most of our experiments were based and which is common in many types of soils (NORDBRING-HERTZ 1988).

Fig. 1:       Schematics of the main structures of nematophagous fungi, which are frequently found by fluorescent microscopy of soil samples:
a) Sporophore and spores of Arthrobotrys; b) sporophore with terminal conidium of Monacrosporium, c) , d) , e) sticky branches and f) connected sticky branches of Monacrosporium (the glue is given by the dots); g) three- dimensional sticky network of Arthrobotrys (glue not given); h) and i) three- celled ring-trap of Arthrobotrys , in i) constricted. Bar represents 20 µm.

Fig. 2.:       SEM of a trap (three-dimensional sticky network) of Arthrobotrys oligospora. Bar represents 100 µm.

Materials and methods:

Results and discussion:

References:

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