INTRODUCTION
Fungi are eukaryotic cells that can exist as unicellular or multicellular organism. They are heterotroph and obtain nutrients by absorbing dissolved organic materials through their cell walls and plasma membrane. They generally prefer more acidic conditions and tolerate high osmotic pressure and lower moisture than bacteria. They are larger than bacteria with more cellular and morphologic details. Primary characteristics such as morphology and cellular detail are used to classify them. They are structurally more complex than bacteria abut are less diverse metabolically.
OBJECTIVES
1. To study morphology of fungi.
2. To emphasize the ubiquitous nature of fungi.
3. To note their nature of reproduction.
4. To outline procedure in identifying fungi.
METHODOLOGY:
A. Unicellular fungi (Yeasts)
Yeasts are non-filamentous unicellular fungi that are typically spherical or oval in shape. They are widely distributed in nature, frequently found in fruits and leaves as a white powdery coating. They reproduce asexually by budding, a process in which new cell forms as protuberance (bud). Sometimes when buds fail to detach themselves a short chain of cells are formed (pseudohypha). Yeasts produce several types of sexual spores, which are used as basis of their classification to different phyla. They are facultative anaerobe and their metabolic activities are used in many industrial fermentations processes. They are used to prepare many foods, including bread and beverages such as wine and beer.
Baker’s yeast
1. Obtain 1.0gram yeast from the stockroom. Add a pinch of sugar and suspend them in tepid water. Let it stand for few minutes then examine under the microscope. Reduce opening of the iris diaphragm to enhance contrast in the specimen.
2. Observe morphology of the yeast in wet mount with Gram iodine. Cover with glass slip and examine under the microscope.
B. Multicellular Fungi (Molds)
Molds have a wide diversity in morphology, which are very useful in classifying them. A macroscopic mold colony is called a thallus, which is composed of mass strands called mycelia. Each strand is a hypha. A vegetative hypha grows in or on the surface of the medium. Aerial hyphae are called reproductive hyphae because they produce a variety of asexual spores. The hyphal strand of most molds is composed of individual cells separated by a cross wall or septum. These hyphae are called septate hyphae. Those hyphae lacking septa are continuous mass of cytoplasm and with multiple nuclei are called coenocytic hyphae.
Fungi are characterized by the appearance of their colony (color, size), hyphal organization (septate or coenocytic) and structure and organization of reproductive spores. Culture techniques and microscopic examination is very important.
1. Obtain a growth from a culture provided by your instructor. Examine the growth macroscopically and note the color, texture, consistency and general appearance of molds growing on the medium.
2. Examine the growth under low power. Tease off some of the mold and transfer to micro slide. Place in a drop of sterile seawater. Carefully position cover slip. Note the appearance of hyphae. Observe nucleus and fruiting bodies. Make some drawings and measurements.
C. Sporulation
1. Transfer the fungus from culture medium to sterile seawater. Measure hyphae of sporulating body. Note appearance of vegetative and reproductive hyphae. Identify other structures and take measurements.
RESULTS AND DSCUSSION:
1. Compare and contrast your yeast from bacteria as to their appearance.
REFERENCES:
Laboratory Exercise No 11
Fungi
Date Performed
Instructor's Signature
RESULTS
RESULTS
Identification of fungus
1. Hyphae stout, measuring 2.5-6.25u, branched, septate, holocarpic, cytoplasmic units travels discharge tubes, measuring 14-25u, discharge tubes form vesicle which contain differentiated spores measuring 3-6u | Lagenidium |
2. Hyphae stout, larger than that of (1), cytoplasmic materials travels and differentiate into spores, absence of vesicles | Serolpidia |
3. Hyphae tubular, extrametrical emerging from discharge tubes thallus may be induced to form discharge tubes | Atkinshiella |
4. Hyphae stout, branched, irregular, non-septate, holocarpic, Irregular due to cytoplasmic constriction, fragments connecting midlike, functions as sporangia,. polygranulytic | Halopthorus |
5. Profusely branched, non-septate mycelium, emerging as cotton wool-like tuffs in the water, hypha vary considerably in diameter between species, reproductive structures separated from somatic hyphae, asexual reproduction by means of biflagellated zoospores | Saprolegnia |
6. Branching hyphae, septate, young culture in Saboraud agar is light buff, changing to light pink to black with the formation of pycnidium which produce unicellular conidia hyphae 50-100u long and 2-3u in diameter | Branchiomycetes |
7. Sporangia filamentous, reproduction occurs during asexual reproduction, no sex organ observed, zoospores 50u, round to oval Variation: Encystmant and germination may be within spherical mass in the apex of emission tube or following rupture of vesicle, extrusion of sporangial contents may or not be followed into spores | Pythium |
8. Produce 4-cell macroconidia and 1-cell microconidia, produce brown pigment in media | Fusarium |
9. Funiculose and olive colored with powder surface, older culture olive black with brown aerial hyphal conidia usually unspetate and occurred singly | Scolebasidium |
10. Reproduction by fragmentation by mycelium into blastospores, arthrospores absent, colonies dry, flat, produce pellicle in liquid media | Candida |
For other groups of fungi please refer to Salle and Frobisher, 1967.
