Worksheet for Morgan/Carter Laboratory #13 Bacteriology Ex. 13-1: INVESTIGATING CHARACTERISTICS OF BACTERIA Lab Study A: Colony Morphology Table 13.1 Characteristics of Bacterial Colonies Name of Bacteria Size Shape Margin Surface Pigmentation 1. 2. 3. Discussion 1. What are the most common colony shapes, margins and surface characteristics found in the species you observed? 2. Based on your observations, comment on the reliability of colony morphology in the identification of different bacterial species? (Is this a good way to distinguish one species from another?) Lab Study B: Morphology of Individual Cells Procedure 1. To become familiar with the basic shapes of bacterial cells using the compound light microscope, examine the prepared slides of three different species and make a sketch in the circles below. Write the name of the species above each sketch.
1. Record the individual cell shapes of the bacteria present on the plaque from your mouth. 2. What bacterial shapes were absent from the plaque? 3. Estimate the relative abundance of each bacterial shape you observed (e.g. more cocci than bacilli). Lab Study C: Identifying Bacteria by the Gram Stain Procedure Table 13.2 Bacteria Observed and of the Gram Stain Name of Bacteria (from the stock used) of the Gram Stain (Gram + or Gram -) 1. 2. 1. What factors can modify the expected result of this Gram staining procedure? Ex. 13-3: BACTERIA IN THE ENVIRONMENT Lab Study A: Investigating Specific Environments Introduction Hypothesis Hypothesize about the presence of bacteria and fungi in different environments. (e.g. What conditions might promote bacterial and fungal growth?)
Prediction Predict the results of the experiment based on your hypothesis. (Note: the environments include: chicken, soil, air, pond water, a plant and washed/unwashed hands.) ** At the next laboratory session, all students will examine the agar plates with bacterial/fungal growth from the environments tested above. You will complete this table at that time. Environment General Description of Growth on the Plate Chicken Soil Air Pond water Plant Hands pre-wash Hands post-wash Discussion 1. How did the plates differ in the number and diversity of different bacterial and fungal colonies? (e.g. shape, color, size, margins, etc.) 2. Did your predictions from the first day of the lab (see Hypothesis) match your results? 3. What environmental and/or growth conditions might have influenced your results?
Lab Study B: Investigating an Environment of Your Choice Introduction What environment did you select to culture? Hypothesis Hypothesize about the possible growth of bacteria you may observe from your environment. Prediction Predict the results of the experiment based on your hypothesis. ** At the next laboratory session, students will examine the growth of bacteria and fungi from the environment selected. 1. What environment did you investigate and under what conditions were the microbes grown? (e.g. time of incubation; temperature; light conditions, etc.) 2. Describe the general characteristics of the bacterial and fungal colonies observed in this experiment. Discussion 1. Do your results match your predictions (see Hypothesis) for the presence of bacteria and fungi in the environment you selected? 2. What factors might be responsible for your results? (e.g. what characteristics of you selected environment might account for your results?)
Ex. 13-3: CONTROLLING THE GROWTH OF BACTERIA Lab Study A: Using Antibiotics to Control Bacterial Growth Introduction Hypothesis Hypothesize about the effect of different antibiotics on the growth of different species of bacteria. (e.g. Will they all be equally effective?) Prediction Predict the results you might observe based on your hypothesis. Procedure Write the names of the species of bacteria and antibiotic applied in the table below. ** At the next laboratory session, students will examine the growth of bacteria on these plates. Use a small metric ruler to measure the radius of the circular zone of inhibition for each of the different antibiotic discs that were used. You can also write: NS = not sensitive; S = sensitive and VS = very sensitive in the box for you data. Bacteria species Anti 1 Anti 2 Anti 3 Anti 4 Anti 5 Anti 6 Anti 7 Anti 8 1. 2. 3.
Lab Study A: Using Antiseptics and Disinfectants to Control Bacterial Growth Introduction Hypothesis Hypothesize about the effect of different antiseptics and disinfectants on the growth of different species of bacteria. (e.g. Will they all be equally effective? Better or worse than antibiotics?) Prediction Predict the results you might observe based on your hypothesis. Procedure Write the names of the species of bacteria and antiseptic/disinfectant applied in the table below. ** At the next laboratory session, students will examine the growth of bacteria on these plates. Use a small metric ruler to measure the radius of the circular zone of inhibition for each of the different antibiotic discs that were used. You can also write: NS = not sensitive; S = sensitive and VS = very sensitive in the box for you data. Bacteria species Agent 1 Agent 2 Agent 3 Control 1. 2. 3. Discussion 1. Do your results match your predictions (see Hypothesis)?
2. Based on the results, which disinfectant is the most and least effective for each species of bacteria? REVIEWING YOUR KNOWLEDGE 1. Define the following terms used in microbiology (use your lab manual, text or other source): sterilize pasteurize nutrient broth agar coccus bacillus spirillum bioflim antibiotic -
antibiotic resistance antiseptic disinfectant peptidoglycan aseptic technique 2. What is the difference between preparing a lawn culture versus a streak culture on an agar plate? 3. What is a zone of inhibition and what does it indicate?