Hectoen Enteric Agar Hectoen Enteric Agar recipe: Yeats Extract, Peptic digest o

Question

Hectoen Enteric Agar

Hectoen Enteric Agar recipe: Yeats Extract, Peptic digest of animal tissue, lactose, sucrose, salicin, bile salts, sodium chloride, sodium thiosulfate, ferric ammonium citrate, bromothymol blue, acid fuchsin, agar, distilled or deionized water.

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

2. Is Hectoen Enteric agar a defined or an undefined medium? Provide the reasoning behind your choice and explain why this formulation is desirable.

3. a.) Growth on the Hectoen Enteric 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!

4. Would removing bile salts from HE agar alter the mediums sensitivity or specificity? Explain your answer.

5. Suppose a mistake is made in preparing a batch of Hectoen Enteric agar and the starting pH is 7.0 instead of 7.4-7.8. Would that affect the medium's sensityvity or specificity? Explain your answer.

6. Write a description of an organism whose colonies are green with black centers on HE agar.

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

Explanation / Answer

1. Peptones which are polypeptides are the source of carbon and nitrogen in the Hectoen Enteric Agar.

2. This belongs to the category of undefined medium as various components are used as a source for amino acids and the exact composition is not known. The media is desirable this way because undefined media supports growth of bacteria and microorganism in a better way because it has more nutrients which are preformed and provides nutritional components for growth.

3. A. Direct viable plate count method is used to check the growth is good or not and this method encompasses serial dilutions from the plates. Selection and preparation of minimal media can be used to check what constitutes good growth.

3.B. 1. This shall not be done because this will result in misinterpreted results.

2. As nutrient agar media is a growth medium for many types of organisms whereas hectoen enteric agar is selection and differential media which is selective for few other organisms.

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