Is macconkey agar chemically defined

Microbiology

Lab 4 Selective Media & Agar BIO250L”

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“Pre-Lab Questions”

1. What is the difference between chemically defined and chemically complex media? Give either a clinical or environmental research example for which each media type would be the most appropriate choice for culturing microorganisms. Click here to enter text.

2. Why is differential media typically inoculated with isolated colonies that have been previously cultured on general growth media? Click here to enter text.

3. Use a textbook or a reputable internet source (such as www.cdc.gov) to research and describe a scenario in a lab or clinical setting in which a selective and/or differential test would be necessary. Click here to enter text.

“EXPERIMENT 1: Bioprospecting for Starch Degrading Bacteria

Data Tables
Table 3: Starch Agar and Gram Iodine Results

Sample

Growth on Starch Agar? (Yes or No)

Clear area around colonies?

Do these bacteria contain amylase?

A

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B

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C

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D

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Post-Lab Questions
1. Why is cow manure used as a potential source of starch-degrading bacteria? (If you are not familiar with the process of digestion in cows, use a reputable internet source to inform your answer.) Click here to enter text.

2. What are some other potential sources of starch-degrading bacteria? Click here to enter text.

3. What component makes starch agar selective for starch-degrading bacteria? Click here to enter text.

4. Why were each of the following steps performed in this experiment?

a. Serial dilution: Click here to enter text.

b. Growth on the nutrient agar plates: Click here to enter text.

c. Streak on the starch agar plates: Click here to enter text.

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“EXPERIMENT 2: Selection and Differentiation of Body Inhabiting Gram-Positive Bacteria

Data Tables
Table 4: Experiment 2 MSA Growth Observations

Surface Tested

Growth (Yes or No) – Nutrient Agar

Growth (Yes or No) – MSA Agar

MSA color around colonies (Red or Yellow)

Other Observations

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Post-Lab Questions
1. What chemical in MSA confers selectivity? How? Click here to enter text.

2. What chemical makes MSA differential? How? Click here to enter text.

3. Why are the nutrient agar plates used in this experiment? Click here to enter text.

4. Was there any growth on you MSA plates? Did any of the colonies change the color of the MSA? What does this tell you about the bacteria taken from each area of your body? Click here to enter text.

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EXPERIMENT 3: Selection and Differentiation of Body Inhabiting Gram-Negative Bacteria from Liquid Samples

Data Tables
Table 5: MacConkey Agar Results

Sample

Growth? (Yes or No)

Colony Color (Clear or Red)

Analysis

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Experiment 3 Post-Lab Questions
1. What types of bacteria are inhibited on MacConkey agar? What ingredient(s) in MacConkey agar selects against those bacteria? Click here to enter text.

2. What ingredient(s) makes MacConkey agar differential? Click here to enter text.

3. Using a textbook and a reputable online source (such as the CDC), research and describe some potentially pathogenic members of the intestinal bacteria family Enterobacteriaceae. Which pathogenic species are lactose fermenters that will grow on MacConkey agar? Click here to enter text.

4. Use a reputable internet source to research and describe some potentially pathogenic intestinal bacteria that do not ferment lactose that will grow on MacConkey agar. Click here to enter text.

5. Use a reputable internet source to research and describe what variations of MacConkey agar can be used to detect other species of bacteria. Click here to enter text.

6. How would you verify that the colonies that grew on a MacConkey agar plate were Gram-negative? Click here to enter text.

7. Look up the formula for MacConkey agar either in a microbiology textbook or online. Is this a chemically defined or a chemically complex media? Why is that important? Click here to enter text.

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