MacConkey Agar MacConkey Agar Recipe: Pancreatic digest of gelatin, pancreatic d

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MacConkey Agar

MacConkey Agar Recipe: Pancreatic digest of gelatin, pancreatic digest of casein, peptic digest of animal tissue, lactose, bile salts, sodium chloride, neutral red, crystal violet, agar, distilled or deionized water.

1. Which ingredients in MacConkey agar supply(ies): (a. Carbon) (b. Nitrogen)?

2. a.) Growth on the MacConkey Agar and Nutrient Agar plates was recorded as ''good growth,'' ''poor growth,'' or ''no growth.'' These are qualitative and, at least for the first two, subjective terms. What did you use to establish what constituted ''good growth?'' b.) Why wouldn't it be advisable to compare growth of the organisms on each plate to each other? There are at least two answers to this question!

Eosin Methylene Blue Agar

Eosin Methylene Blue Agar Recipe: Pancreatic digest of gelatin, lactose, dipotassium phosphate, methylene blue, Eosin Y, agar, distilled or deionized water.

3.) Which ingredients in Eosin Methylene Blue agar supply(ies): (a. Carbon) (b. Nitrogen)?

4.) a.) Growth on the EMB Agar and Nutrient Agar plates was recorded as ''good growth,'' ''poor growth,'' or ''no growth.'' These are qualitative and, at least for the first two, subjective terms. What did you use to establish what constituted ''good growth?'' b.) Why wouldn't it be advisable to compare growth of the organisms on each plate to each other? There are at least two answers to this question!

5.) Would removing eosin Y and/or methylene blue from EMB agar alter the medium's sensitivity or specificity? Explain your answer.

6.) Suppose a mistake is made in preparing a batch of EMB agar and the starting pH is 7.6 instead of 6.9-7.3. Would that affect the medium's sensityvity or specificity? Explain your answer.

I WOULD REALLY APPRECIATE SOME HELP WITH THESE QUESTIONS. I WILL RATE CORRECT ANSWERS. THANK YOUR VERY MUCH. MICROBIOLOGY LAB.

Explanation / Answer

1. a. Lactose in MacConkey agar provides carbon.

b. Pancreatic digest of Casein, Gelatin and Animal tissue provide nitrogen.

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