Activity 8.1.2 – Rounds, Rods, and Spirals

 

Purpose

Many illnesses are caused by organisms so small they cannot be seen without magnification. Harmful bacteria, fungi, and protozoa are often the culprits. Disease-causing bacteria and protozoa invade the cells of a host, feeding from those cells or excreting a toxin that makes the host ill. Harmful fungi can attack living tissues and may also produce allergy causing spores and toxins in foods. One type of harmful fungi is mold. While there are many beneficial or harmless bacteria, fungi, and protozoa, these three organisms are the cause of many diseases and illnesses.

 

Identifying microorganisms is necessary in disease identification, treatment, and prevention, but can be a difficult task due to their small size. Microscopes are a useful tool for exploring the world of microorganisms. However, as you saw in the presentation on viruses, they are so small that they can only be seen with special high-powered microscopes.

 

Equipment

Per pair of students: ·        Microscope ·        Bacteria slide ·        Mold slide ·        Protozoa slide

Per student: ·        Pencil ·        Agriscience Notebook

 

Procedure

In this activity, you will work with a partner to identify and sketch several disease-causing organisms. You and you partner will view three slides containing bacteria, molds, and protozoa. Use care and caution when handling the microscope and slides to avoid breaking the slides.

 

Part One – Bacteria

1.      Obtain a bacteria slide.

2.      Hold it up against a light background to note the three stained streaks on the slide. Place the slide on the microscope under low power.

3.      Locate a stained area, and focus the microscope.

4.      Switch to the the high-power objective and focus carefully.

5.      Identify, sketch, and label the specific bacteria type in that area in Table 1. Use your notes from the Infectious Disease Causing Agents presentation to help you identify the bacteria you are viewing.

6.      Repeat for the other two stained areas on the slide.

Table 1. Bacteria
Section 1	Section 2	Section 3
Type:	Type:	Type:

 

Part Two – Mold

Obtain a mold slide and repeat the procedures from Part One recording your observations in Table 2.

 

Table 2. Mold
Section 1	Section 2	Section 3
Type:	Type:	Type:

 

Part Three – Protozoa

Find two different protozoa on the slide and sketch them in Table 3. Draw as much detail as possible, including the cell organelles.

 

Table 3. Protozoa
Sketch 1	Sketch 2

 

 

Conclusion

1.      What structural differences did you observe between bacteria, molds, and protozoa?

 

 

 

 

 

 

2.      Based on your observations, what challenges might epidemiologists encounter when trying to identify the source of an illness?