Day 2 - Viewing a prepared slide of mixed bacteria on high power.

Transcription

1 Purpose Bacteria Lab To compare the quantity and the different types of bacteria from four different locations within the school. To identify 3 different bacterial colonies on a prepared slide. Materials per group of 2 people 2 sterile Petri dishes containing nutrient agar Microscope Marking pen Prepared Slide Mixed Bacteria Tape Procedure Day 1 Part A Bacteria Around the School 1. On the bottom of an agar plate, mark the letters A, B, C, and D in each of the four quadrants. Write your name on the bottom of the plate (the side with the agar on it). 2. Choose four different locations in the school, two that you think will have lots of bacteria and two that you think will be clean. Record these locations on your observations chart (A&B should be your dirty locations and C&D should be your clean locations). Keep in mind that damp locations will contain mold, which will inhibit bacterial growth. Use tape to collect and transfer bacteria to the sterile agar plate. Only open the agar plate when it is upside down and be gentle agar has the consistency of jello. 3. Cover the plate and place it upside down in the incubator. A B C D Day 2 - Viewing a prepared slide of mixed bacteria on high power. 1. Once your slide is focused on low power and then medium power, increase the magnification to high power by rotating the nosepiece to the lens that reads 40x. 2. Use the fine focus knob to refine the focus of the image. 3. If the image is too dark, adjust the diaphragm. 4. Draw a biology diagram of exactly what you see. Remember: use pencil. 5. Identify 2 different bacterial colonies (look for different shapes). Label your diagram to indicate the shape of the bacteria you found.

2 6. Give the apparent magnification of your diagram and calculate actual length of your 2 bacterial shapes. Day 3 Bacteria around the School 1. Observe your agar plate. Do not remove the lid of your agar plate during your observations. If the lid is foggy, open the plate upside down, rinse and dry the lid and then replace it. 2. Draw a map of the bacterial colonies that have grown over the incubation period. Colour any colonies that have colour. Number each different colony starting in quadrant A. All colonies should have a number and those that have the same appearance (colour, shape and shininess) should have the same number. 3. Complete the chart of observations.

3 Observations Map of colonies (5 marks) Bacteria Around the School Chart of Observations (8 marks) Site & Location A Total # of Colonies # of different colonies Description of colonies (including colour, shape, and shininess) B C D

4 Discussion questions: 1. How does the field of view diameter change as the magnification of the microscope increases? (i.e. is the field of view getting larger or smaller?) (2 marks) 2. Describe the steps you would take to view a slide sample on high power. (3 marks) 3. Describe 3 ways in which bacteria can be identified. (3 marks) 4. How does Gram stain help identify bacteria? What color are Gram-positive and Gram-negative bacteria? (3 marks) 5. Identify the six types of bacteria shown (A-3, H) according to the bacteria shape and growth pattern (6 marks). A = B = C = D = E = H =

5 6. A microbiology lab has come to you with a sample from a patient (shown to the right). The patient has been exhibiting symptoms of pneumonia. Help the microbiology lab determine what is plaguing the patient by identifying the type of bacteria shown (i.e. name the bacteria according to the bacteria shape and growth pattern). (2 marks) Conclusion Which location had the most bacteria? Why do you think that they were so abundant in that location? Which location had the greatest number of different types of bacteria? Where do you think that all of these different types have come from? How can you avoid being infected by the bacteria in our school in the future?