BIO 1116 General Biology Lab Name: Instructor Name: Lab Day: Section: A or B (Circle One) Lab #2: Bacteriology Exercise 1: 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 on the reliability of colony morphology in the identification of a given bacterial species. Table 1: Characteristics of Bacterial Colonies (3 pts) 1. 2. 3. Name of Bacteria Size Shape Margin Surface Color Lab Study B: Morphology of Individual Cells (3 pts) 1. To become familiar with the basic shapes of bacterial cells, using the compound microscope, examine prepared slides of the (3) general types/shapes of bacteria, and make a sketch of each shape in the space provided. Include Title, Total Mag. For each drawing. 1
2. Observations on bacteria found in plaque. a. Record the individual cell shapes of bacteria present in your plaque. b. Which shapes appear to be absent? c. Estimate the relative abundance of each shape (rough percent composition of each in your sample). 3. Discuss with your lab partner information you have learned from your dentist or health class etc., about the relationship among plaque, dental caries (cavities), and gum disease. Briefly summarize your finding below. 4. Suggest an explanation for differences in the proportion of each type of bacteria in the bacterial community of plaque. (Hint: Think about this in the context of diet, hygiene, and bacterial succession.) (2 pts) Lab Study C: Identifying Bacteria by the Gram Stain Procedure Table 2: Bacteria Observed and Results of the Gram Stain (2 pts) Species of Bacteria Results of Gram Stain (Color/Positive or Negative) Discussion: 1. Why do we stain bacterial cells? What does staining permit us to visualize? (2 pts) 2
2. Which of the bacterial species observed during the Gram Stain procedure are probably more closely related taxonomically? (Hint: Think about what the Gram Stain does.) (2 pts) 3. Regarding methodology of the Gram Staining technique, what factors can affect the outcome, or expected results of this staining procedure? (2 pts) Exercise 2: Ecological Succession of Bacteria in Milk (4 pts) Scenario: Propose a hypothesis for bacterial succession in each type (white/chocolate) of milk. White: Chocolate: 3
Table 3: Physical Features and Bacterial/Fungal Communities of Aged Plain and Chocolate Milk (8 pts) Age/Type of Milk Environmental Characteristics (ph, consistency, color, odor) Organisms Present (Bacteria: G(+) or (-), shapes) Fungi, yeasts, molds Refrigerated White 24 Hour White 4-Day White 8-Day White Refrigerated Chocolate 24 Hour Chocolate 4-Day Chocolate 8-Day Chocolate 4
Discussion: 1. Describe the changing sequence of organisms and corresponding environmental changes during succession in white milk. Do the results of your investigation match your hypothesis? (2 pts) 2. Describe the changing sequence of organisms and corresponding environmental changes during succession in chocolate milk. Do the results of your investigation match your hypothesis? (2 pts) 3. Compare succession in white and chocolate milk. Propose reasons for any observed differences.(3pts) 4. Propose an experiment to test the environmental factors and/or organisms changing in your proposed scenario for milk succession. (2 pts) 5
Exercise 3: Bacteria in the Environment Experiment A: Investigating Specific Environments Hypothesis: Propose a hypothesis about the presence of bacteria and fungi in the (4) different sampling environments. (2 pts) Prediction/Expected Results: Based on your hypothesis, what do you expect to find in your sampling environments? Results Table 4: Abundance and types of colonies associated with food, soil, air, water, hands (6 pts) Environme Colony Type(s) and Abundance Food: (Chicken, Meat, nt Fish) Soil Lab Air Water (Tap) Water (Fountain) Hands before washing Hands after washing Mouth before mouthwash Mouth after mouthwash 6
Exercise 4: Controlling the Growth of Bacteria- Antibiotics, Antiseptics, Disinfectants Hypothesis: Develop a hypothesis about the effect of different antibiotics on the growth of bacteria. (2pts) Prediction: What do you think the outcome will be regarding the effectiveness of the chosen antibiotics? Hypothesis: Develop a hypothesis about the effect of different antiseptics and disinfectants on the growth of bacteria. (2 pts) Prediction: What do you think the outcome will be regarding the effectiveness of the chosen antiseptics and disinfectants? Table 5: Results of Antibiotic and Antiseptic/Disinfectant Sensitivity Tests (all measurements in mm) For bacteria, use Table of Standards for interpretation found on blackboard. For Antiseptics/Disinfectants use the standards in the lab manual on page 50. (8 pts) Bacteri al Species / Gram (+) or (-) 1. Antibiotic Antiseptic/Disinfectant 2. 3. 4. 7
Discussion: 1. For the antibiotics, did your results support your hypothesis? Was the zone of inhibition the same for all bacterial species? (2 pts) 2. Were any bacteria very sensitive/susceptible to all antibiotics tested? If so, which? (2 pts) 3. Based on your results, which antibiotic would you prescribe for each bacterial species? (2 pts) 4. Were the results different for Gram (+) and (-) bacteria? (2 pts) 5. For the antiseptics/disinfectants, did your results support your hypothesis? Explain. (2 pts) 6. Based on your results, which disinfectant is most effective in controlling the growth of bacteria? (1 pt) 7. When would you use disinfectants & when would you use antiseptics? Why can t you use both in every case?(3 pts) 8
Applying Your Knowledge (5 pts/ea) 1. Would you expect the community of bacteria in plaque sampled 1 week after you have had your teeth cleaned to differ from the community of bacteria found 1 week before you have your teeth cleaned? Explain. 2. Bacterial species that are harmful, as well as others that are beneficial, are found in the living body. To slow the rate of developing antibiotic resistance in bacteria, physicians are being encouraged to use narrowspectrum antibiotics- those that target only a few bacterial types. How can the information learned by antibiotic sensitivity testing be used by physicians who must choose antibiotics that inhibit the growth of bacteria causing disease, but that do not interfere with beneficial bacteria? 3. Death rates due to infectious diseases declined steadily in the United States and western Europe throughout most of the 20 th century. However, since the 1980 s, infectious disease-related deaths are increasing significantly, especially in the United States. Propose possible factors that may be contributing to the observed increases. 4. Biologists have observed that many species of bacteria and fungi are capable of producing antibiotics that will inhibit the growth of bacterial species. In their natural environment, what would be the adaptive advantage of producing these antimicrobial agents? 9