Laboratory Exercise #5
Identification of Fungi
Fungi, like bacteria, may be useful in industry but also problematic. Many produce important products including foods, chemicals, enzymes and pharmaceuticals such as antibiotics and hormones. Molds, however, in particular, are also common contaminants in industry. It is important to be able to recognize and identify them, therefore, in the laboratory. In today’s laboratory session you will examine some common molds and attempt to identify them. While the identification of bacteria relies heavily on biochemical testing, the identification of molds tends to focus on their structural features. You will examine the appearance of growing cultures of several different molds and then prepare wet mounts of each to examine microscopically. Your instructor will provide you with a ‘key’ which includes information regarding some of the more common molds. You will use this key to identify the lab isolates. You will also prepare wet mounts of a yeast culture and use the ocular micrometer of your microscope to measure these cells for comparison to bacterial cells.
Part A: Molds
1. Obtain an agar plate culture of an ‘unknown’ mold. All molds have been cultured on Sabouraud’s dextrose agar (SDA).
2. Visually examine the culture. A dissecting (or stereo-) microscope may be useful for this purpose.
a. colour or pigmentation of the culture
b. texture (powdery, viscous, etc.)
3. Obtain a clean microscope slide and add 1-2 drops of lactophenol cotton blue (stain) to it.
4. Obtain a short piece of cellophane tape. Be careful to touch it only at the two ends.
5. Press the ‘sticky side’ down onto the surface of the mold culture. If there are different colours present in the culture, try to ‘pick up’ a portion of each. Spores may be a different colour than the mycelia – usually darker. Remember that you want to keep the reproductive structure (the part of the mold where the spores...
Please join StudyMode to read the full document