LAB 10: The Eukaryotes
Objectives
In this lab, you will:
1. Learn about the characteristics of fungi, protozoa and helminthes, including pathogenic species.
2. Observe prepared slides and agar plates with several types of fungi including yeasts and molds.
3. Observe prepared slides of several protozoan pathogens, and live protozoans in a lake water sample.
4. Observe prepared slides and preserved specimens of parasitic worms.
5. Prepare a collective forehead swab for microbial identification in Lab 12.
Key Terms: Fungi, heterotroph, saprotroph, mold, hyphae, mycelium, aerial (reproductive) hyphae,
vegetative hyphae, thermal dimorphism, yeast, budding, opportunistic infections, Zygomycete,
Ascomycete, Basidiomycete, ascospore, conidiospore, sporangiospore, zygospore, basidiospore, protozoa,
vector, Amoebozoans, ciliates, flagellates, apicomplexans, cyst, trophozoite, helminthes, Platyhelminthes,
cestodes, trematodes, nematodes, mode of transmission.
Introduction
So far our laboratory exercises have been primarily focused on prokaryotic organisms—those that lack a
nucleus and other membrane-bound organelles. However, there are other types of eukaryotic microorganisms
that exist in nature, some of which cause human disease. In this exercise we will examine representative types
of eukaryotic microorganisms: fungi, protozoa, and parasitic worms (helminthes), and learn about the diseases
that they cause.
The Fungi
Fungi are heterotrophs (organisms that require organic carbon). In nature they are important saprotrophs-
organisms that decompose dead organic matter. Many fungi produce enzymes that decompose woody plant
material—thus making them of critical importance for nutrient recycling in forests. Some types of fungi live in
a symbiotic relationship with a photosynthetic algae or bacterium (lichens)—others live in symbiosis with plant
roots (mycorrhizae). Fungi are also an important food source for humans and other organisms, and are used in
food production as well. Fungi have a cell wall composed primarily of chitin (a polymer of glucose).
Members of the Kingdom Fungi exist as multinucleate filaments (molds) or unicellular yeasts. Molds have
long branching cellular structures called hyphae that grow continuously without complete division of
cytoplasm. Several hyphae may form a visible mat called mycelium. Most hyphae grow along the substrate
(vegetative hyphae) but those that produce spores extend upwards to disperse them (aerial or reproductive
hyphae). Hyphae may or may not have septa that partially separate the cytoplasm (Figure 1).