LAB Book Used: Leboffe and Pierce (2016). Brief microbiology laboratory theory and application (3rd ed.) Englewood, CO: Morton Publishing.

ISBN: 9781617314773

Exercise 2-13 (Chemical Germicides: Disinfectants and Antiseptics)

1. The concentrations of the potential germicides are very different. Why is ok to compare these agents at different concentrations?

2. Which agent would your PREDICT would have the greatest antimicrobial effect? Why?

3. This exercise uses FOUR control tubes. Each control tube is used to check on a different aspect of the experiment. For each control tube, indicate what the tube is checking for. “To see what the result looks like” is incorrect for all four tubes.

4. Four agents were tested in this experiment, which agent do you think worked best against E. coli? Explain your thinking. Four agents were tested in this experiment, which agent do you think worked best against B. subtilis? Explain your thinking.

5. In another time, in another place, the petri dishes were not been washed well between lab sessions. Some sections noticed that the disinfectants seemed to work better in these unwashed dishes and other students noticed that the agents seemed to work less well. Stretch your thinking. What might lead to an improvement in results or a diminishing of results? Discuss both outcomes.

Exercise 5-4 (Catalase)

1. Only cells that do aerobic respiration make catalase. What does catalase do for these cells? What are the bubbles formed in the catalase reaction made of? What is the complete reaction for the breakdown of hydrogen peroxide by catalase?

Exercise 5-6 (Nitrate Reduction)

2. What are the different potential products of nitrate reduction?

3. Why must you know whether an organism is a fermenter or not in order to determine whether any gas observed in the tube is from denitrification?

Exercise 3-13 ( Microscopic Examination of Eukaryotic Microbes)

4. What are three things you might have observed in the slides of the protists that would tell you that you were looking at protists and not bacteria? Be sure the items you list are present in the observation sheet you submit.

5. Why is it easier to differentiate ticks from fleas, mites, and mosquitoes than it is to differentiate the cercaria of the Schistosoma mansoni from the Giardia lamblia?

Exercise 2-1 (Ubiquity of Organisms)

1. What does it mean to be ubiquitous?2. What is the purpose of plates 7 and 8?3. What are two variables being testing in this exercise?4. What is the purpose of rolling the swab as you streak it across the agar surface (and the sampled surface)?