Morgan-Carter Lab #12 BACTERIOLOGY

1 Name _____ Morgan-Carter Lab # 12 bacteriology Ex. Investigating Characteristics of Bacteria Lab Study A: Colony Morphology 1. What are the most common colony shapes, colony margins, and colony surface characteristics found in the species observed by you and your lab partner? 2. Based on your observations, comment of the reliability of colony morphology in the identification of a given bacterial species. Table Characteristics of Bacterial Colonies Name of Bacteria Size Shape Margin Surface Pigmentation 1. 2. 3. Lab Study B: Morphology of Individual Cells 1. To become familiar with the basic shapes of bacterial cells, using the compound microscope, examine prepared slides of the three types of bacteria, and make a sketch of each shape below.

2 2. Indicate the individual cell shapes of bacteria present in plaque and estimate the relative abundance of each. 3. What shapes are absent? Lab Study C: Identifying Bacteria by the Gram Stain Procedure Table Bacteria Observed and Results of Gram Stain Name of Bacteria Results of Gram Stain 1. 2. Name of Bacteria Results of Gram Stain 3. 4. 1. Which of the bacteria observed are probably more closely related taxonomically? 2. What factors can modify the expected results of this staining procedure? Ex. Ecological Succession of Bacteria in Milk Table Physical Features and Bacterial/Fungal Communities of Aged Plain and Chocolate Milk Age/Type of Milk Environmental Characteristics Organisms Present Refrigerated plain 24-hr plain 4-day plain 8-day plain Refrigerated chocolate 24-hr chocolate 4-day chocolate 8-day chocolate 1.

3 Describe the changing sequence of organisms and corresponding environmental changes during succession in plain milk. 2. Describe the changing sequence of organisms and corresponding environmental changes during succession in chocolate milk. 3. Compare succession in plain and chocolate milk. Propose reasons for differences. 4. Propose an experiment to test the environmental factors and /or organisms changing in your proposed scenario for milk succession. Ex. Bacteria in the Environment Experiment A: Investigating Specific Environments Table Abundance and Types of Colonies Associated with Food, Soil, Air, etc Environment Chicken Soil Air Pond water Plant leaf Hands before washing Hands after washing 1. How did the plates differ in the number and diversity of bacterial and fungal colonies?

4 2. What factors might be responsible for your results? Experiment B: Investigating the Environment of your choice 1. What environment did you investigate? Indicate any treatment you applied. 2. Characterize the bacterial and fungal colonies from your experiment. Ex. Controlling the Growth of Bacteria Lab Study A: Using Antibiotics to Control Bacterial Growth Table Results of Antibiotic Sensitivity Tests (size of inhibition zones in cm) Bacteria Antibiotic (Name, Gram +/-) 1. 2. 3. 4. 1. Was the zone of the inhibition the same for all bacteria? 2. Were any bacteria very sensitive (>1 cm) to all antibiotics? If so, which bacteria? 3. Based on your results, which antibiotic would you prescribe for each organism?

5 4. Were the results different for Gram-positive and Gram-negative bacteria? 5. Can you think of alternative explanations for the differential effectiveness of some antibiotics? Lab Study B: Using Antiseptics and Disinfectants to Control Bacterial Growth Hypothesize about whether antiseptics or disinfectants will be more effective at controlling bacterial growth. Predict the results of the experiment based on your hypothesis. Table Results of Sensitivity Tests of Antiseptics and Disinfectants (size of inhibition zones in cm) Bacteria Antiseptic OR Disinfect. (Name, Gram +/-) 1. 2. 3. 4. 5. 1. Did your results support your hypothesis? Explain. 2. Based on your results, which disinfectant is most effective in controlling the growth of bacteria?

6 3. Which antiseptic is most effective? 4. In which situations is it appropriate to use a disinfectant? An antiseptic? REVIEWING YOUR KNOWLEDGE 1. Once you have completed this lab topic, you should be able to define and use the following terms, providing examples if appropriate: Sterilize Pasteurize Nutrient broth and agar Coccus Bacillus Spirillum Biofilm Antibiotic Antibiotic resistance Antiseptic Disinfectant Peptidoglycan Aseptic technique 2. Return to Figure and observe the zones of inhibition for each antibiotic disk. a. What is the significance of the clear zone around the disks? b. Is the bacterium growing on this plate resistant to any of the antibiotics being tested here? 3. A liquid that has been sterilized may be considered pasteurized, but one that has been pasteurized may not be considered sterilized.

7 Why not?