BIO 105 Science of Biology w/Lab

Differential and Biochemical Tests

PRE-LAB QUESTIONS

1. Based on the scientific name Streptococcus agalactiae, what morphology would you expect these cells to have?

2. Name at least three animal structures that would be analogous to bacterial flagella.

3. Hypothesize how over-washing of hands can affect the population of “good” bacteria that resides on human skin.

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Differential and Biochemical Tests

EXPERIMENT 1: ANTIBIOTIC SENSITIVITY

Data Tables

Purpose (What question is this experiment designed to answer?):

Hypothesis (Based on what you’ve learned in the pre-lab materials, write and If/Then statement regarding the outcome of this experiment.):

Table 1: Zone of Inhibition for Skin Sample

Table 2: Zone of Inhibition for Local Sample

Table 3: Zone of Inhibition for Yeast Sample

Claim (What are the results of your experiment?):

Evidence (What data did you collect that supports your claim? Explain the meaning behind the data and the calculations.):

Antibiotic Disk Diameter of Zone (mm)

AM10

K30

Te30

Antibiotic Disk Diameter of Zone (mm)

AM10

K30

Te30

Antibiotic Disk Diameter of Zone (mm)

AM10

K30

Te30

©eScience Labs, 2021

Differential and Biochemical Tests

Post-Lab Questions

1. Table 4 outlines interpretive standards of antibiotic resistance based on the size of inhibition zones. For example, many bacterial species that are resistant to Kanamycin have an inhibition zone of 13 mm or smaller. Of course, inhibition zones may also be affected by the antibiotic concentration present within the disk. Use Table 4 to determine whether the microbial samples you tested are sensitive (S), moderately resistant (MR), or resistant (R) to each of the antibiotic disks. Remember, you will not know the exact species of bacteria on your “Skin” and “Local” plates. The table is a guide to compare your results to a standard.

2. Is the bacterial lawn sampled from your skin more resistant to one antibiotic than the others? What about the local sample? The yeast sample? Use your results from Question 1 to support your answer.

3. What can you say about the antibiotic susceptibility of the microorganisms you cultured?

4. Use a reputable internet source to determine why these antibiotics prevent binary fission in certain bacterial species.

5. Research and describe the relationship between the minimum inhibitory concentration (MIC) and the zone of inhibition. What can you determine about the MIC and the effectiveness of the antibiotics used in this experiment? Note, disk potencies are listed per antibiotic in the Materials section before the experimental procedure.

Reflection (Discuss what you have learned by doing this experiment. How have your ideas changed? Do you have any new questions? What connections did you make between the lab and lecture?):

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