Immune Lab

This lab is designed to provide you with hands-on experience in examining the microscopic structures of lymphatic tissues and comparing bacterial samples collected from various sources. By the end of this lab, you will have a deeper understanding of the role of lymphatic tissues in the immune system and the diversity of bacterial populations in our bodies and environment.

Objectives

· Identify and describe the key structures and functions of lymphatic tissues, including tonsils, spleen, lymph nodes, and appendix.

· Compare and contrast the structures of different lymphatic tissues, noting their similarities and differences.

· Collect and process bacterial samples from personal and environmental sources using aseptic techniques.

· Observe and analyze the diversity of bacterial colonies grown from collected samples.

· Compare and contrast the morphology and characteristics of bacterial colonies from different sources.

· Develop an understanding of the role of lymphatic tissues in the immune system and the importance of bacterial diversity in our bodies and environment.

Materials

· Microscope

· Prepared Lymphatic Slides

· Empty Glass Slides

· Sterile Cotton Tipped Applicators

· Bunsen burner

· Crystal Violet

· Gram’s Iodine

· Ethanol

· Safranin

Micrographs of Lymphatic Tissues

In the first part of the lab, we will focus on the examination of lymphatic tissues, including tonsils, spleen, lymph nodes, and the appendix. These tissues play a crucial role in our immune system, helping to filter and eliminate harmful substances from our bodies.

1. Obtain prepared slides of tonsils, spleen, lymph nodes, and appendix.

2. Using a light microscope, examine each slide at low, medium, and high magnification.

3. Identify and label the key structures in each tissue, such as germinal centers, lymphatic nodules, and white pulp.

4. Take micrographs of each tissue using a camera attachment or a smartphone adapter for the microscope.

5. Compare and contrast the different lymphatic tissues, noting their similarities and differences in structure and function.

What happens if the tonsils became infected. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Draw a micrograph of a tonsil slide.

What happens if the spleen became infected. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Draw a micrograph of a spleen slide.

What happens if lymph nodes become infected. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Draw a micrograph of a lymph node slide.

What happens if the appendix became infected.
________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Draw a micrograph of an appendix slide.

Comparing Bacterial Samples

In the second part of the lab, we will be comparing bacterial samples collected from your nose, mouth, and environmental sources. This exercise will allow you to observe the diversity of bacterial populations and understand the role of bacteria in our bodies and surroundings.

1. Collect swab samples from your nose and mouth using sterile cotton swabs. Also, collect three environmental samples from surfaces such as a phone, desk, etc.

2. Prepare a bacterial smear, one at a time:

a. Place a small drop of water on a clean microscope slide.

b. Using a sterile loop or swab, transfer a small amount of bacterial culture to the water drop and mix gently.

c. Spread the mixture into a thin, even layer across the slide.

d. Allow the smear to air-dry completely.

e. Heat-fix the smear by passing the slide through a flame several times, smear side up, to prevent the bacteria from washing off during staining.

3. Apply crystal violet stain:

a. Flood the slide with crystal violet stain and let it sit for 1 minute.

b. Gently rinse the slide with distilled water to remove excess crystal violet.

4. Apply iodine solution (Gram's iodine):

a. Flood the slide with iodine solution and let it sit for 1 minute. The iodine acts as a mordant, forming a complex with the crystal violet.

b. Gently rinse the slide with distilled water to remove excess iodine.

5. Decolorize with ethanol:

a. Apply ethanol to the slide for 15 seconds, or until the purple color stops running off the slide. This step is critical, as it differentiates Gram-positive from Gram-negative bacteria.

b. Gently rinse the slide with distilled water immediately after decolorization to stop the action of the alcohol or acetone.

6. Counterstain with safranin:

a. Flood the slide with safranin and let it sit for 1 minute. This stain will color the Gram-negative bacteria pink or red.

b. Gently rinse the slide with distilled water to remove excess safranin.

7. Dry and examine the slide:

a. Gently blot the slide with bibulous paper or a paper towel to remove excess water without disturbing the bacterial smear.

b. Allow the slide to air-dry completely.

8. Using a light microscope, examine the morphology of the bacterial colonies at low, medium, and high magnification.

9. Compare and contrast the bacterial samples, noting differences in colony appearance, color, and morphology.

Observation

Bacterial morphology refers to the shape and arrangement of bacterial cells. There are three primary shapes of bacteria:

· Cocci (singular: coccus) - These are spherical or round-shaped bacteria. They can be found as single cells, in pairs (diplococci), in chains (streptococci), in clusters (staphylococci), or in other arrangements.

· Bacilli (singular: bacillus) - These are rod-shaped bacteria. They can be found as single cells, in pairs (diplobacilli), in chains (streptobacilli), or with other arrangements. Some bacilli have a slightly curved shape, called vibrios.

· Spirilla (singular: spirillum) - These are spiral-shaped bacteria, resembling a corkscrew. They can be found as single cells or occasionally in chains.

The Gram stain result is a classification of bacteria based on the properties of their cell walls. There are two main groups:

· Gram-positive bacteria - These bacteria have a thick layer of peptidoglycan in their cell walls, which retains the crystal violet-iodine complex during the Gram staining procedure. As a result, they appear purple or blue under the microscope. Examples of Gram-positive bacteria include Staphylococcus aureus, Streptococcus pyogenes, and Bacillus subtilis.

· Gram-negative bacteria - These bacteria have a thin layer of peptidoglycan and an outer membrane containing lipopolysaccharides. The outer membrane prevents the crystal violet-iodine complex from binding to the peptidoglycan layer during the Gram staining procedure, so they are decolorized by the alcohol or acetone and take up the counterstain safranin. They appear pink or red under the microscope. Examples of Gram-negative bacteria include Escherichia coli, Pseudomonas aeruginosa, and Salmonella enterica.

By combining morphology and Gram stain results, we can describe bacteria more specifically. For example, Staphylococcus aureus is a Gram-positive coccus, while Escherichia coli is a Gram-negative bacillus.

Describe the nasal bacterial sample. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________