BIO 175 Lab 7 - Selective Media and Agar PDF

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Selective Media and Agar...

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BIO 175 Online Lab 7: Selective Media and Agar Pre-Lab Question (5pts) 1. Why is differential media typically inoculated with isolated colonies that have been previously cultured on general growth media? a. It allows the growth of certain bacteria. This allows organisms to be visually different.

Experiment 1 Results Tables Complete Table 1 with your results (15 pts). Sampl e

Growth on Starch Agar? (Yes or No)

Clear area around colonies?

Do these bacteria contain amylase?

A

Y

N

N

B

Y

N

N

C

Y

N

N

D

Y

Y

Y

Table 1: Starch Agar and Gram Iodine Results

Experiment 1 Post-Lab Questions (5pts) 1. Explain why each of the following steps performed in this experiment? a. Serial dilution: i. It reduces the number of colonies which makes it easier to manage. b. Growth on the nutrient agar plates: i. So that all bacteria can grow and be isolated. c. Streak on the starch agar plates: i. It was used to isolate the sample and to show the existence of bacteria that would break down starch

Experiment 2 Photograph Post two photographs of your results below. Be sure to include: one close-up of your results along with your personal token and a second photo of a selfie with your results (5 pts. ea./ 10pts total).

Experiment 2 Results Tables Complete Table 2 with your results (20 pts). Table 2: Experiment 2 MSA Growth Observations

Growth (Yes or No)

Growth (Yes or No)

Nutrient Agar

MSA Agar

MSA color around colonies (Red or Yellow)

1. Skin

N

N

N/A

2. Nose

Y

Y

Yellow

3. Table

Y

N

N/A

4. Control

N

N

N/A

Surface Tested

Other observations

Experiment 2 Post-Lab Questions (10pts) 1. What chemical in MSA confers selectivity? How? a. Mannitol because it’s used for fermentation. 2. Why are the nutrient agar plates used in this experiment? a. Nutrient agar allows all bacteria to grow and shows the difference between various colonies.

Experiment 3 Results Tables Complete Table 3 with your results (25 pts). Table 3: MacConkey Agar Results Colony Color

Growth? (Yes or No)

(Clear or Red)

1. Fountain Water

N

N/A

2. Rain Water

Y

Red

3. Faucet Water

N

N/A

Sample

Analysis of results

Lactose Fermentation

Experiment 3 Post-Lab Question (10pts) 1. 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? a. E. coli, Citrobacter, and Klebsiella 2. How would you verify that the colonies that grew on a MacConkey agar plate were Gram-negative? a. MacConkey Agar is selective to only gram-negative bacteria. Bile salts and crystal violet makes it difficult for gram-positive bacteria to grow....