A LOOK AT FUNGI

One of the truly great things about living in humid, subtropical Florida is that fungi are so readily obtainable. Approximately 50,000 species of fungi exist in the kingdom Mycota (Fungi). Why, just scraping the walls near damp areas, such as shower stalls, is sure to uncover some or, possibly, all of them! A more reliable source year-round is the garden or lawn. Shaking a few leaves of any outdoor plant over an opened petri dish filled with Sabouraud Dextrose Agar is sure to delight the budding mycologist! Fungal spores alight on the smooth surface. Within two to three days, a promising mass (mycelium) of cottony filaments (hyphae) becomes evident where a spore has succeeded in rooting. This potluck approach is what I used to grow the fungi shown below. Bearing in mind that some of these molds may be particularly hazardous when they get ready to sporulate in earnest should encourage rapid harvesting of interesting specimens.

Sometimes, the fungal hyphae walls may autofluoresce under UV with no further treatment. The walls are composed of cellulose or chitin. Generally, a fluorescent dye that stains the walls of the hyphae is needed. One such dye is Calcofluor. A few drops of a 1% buffered, aqueous solution of Calcofluor were allowed to act on the mycelium for some minutes before exposing the fungus to a UV LED light. A suitable blocking filter was rotated into place to allow the longer, fluorescence-emission wavelengths (> 425 nm) to pass through to the CCD camera.

NOTE: Of those shown above, the only mold that I can identify with certainty, at least down to the genus level, is the Penicillium species in the second row, right.

In addition to employing Calcofluor as a wall-staining dye, Fluorescein Diacetate (FDA) was used to test for viability of a fungal organism. In solution, FDA is a very weak fluorescent dye. In a living cell, enzymes (called esterases) exist in the cytosol that can cleave the two acetate molecules from the FDA molecule leaving highly fluorescent Fluorescein. Under blue light, Fluorescein glows with a brilliant yellow-green hue, as seen in the last two photos.

The UV LED diode used has a peak emission at 395 nm in the near UV. To excite the FDA, an LED operating at 470 nm was used. A blocking filter passing wavelengths above 515 nm was then rotated into place. The above images were captured with a monochrome Mintron 12V1E-EX camera and pseudocolored to simulate the eye's view.