University:
Amherst College
Course:
BIOL 191 | Molecules, Genes and Cells
Academic year:

2022
Views:

305

Pages:

4
Author:

folclord7m

Exercise 12 Laboratory Report Special Media for Isolating Bacteria Purpose Hypotheses 1. Bacteria growing on EMB agar will be gram . 2. Which media will be selective? Differential? Results Organism Nutrient Agar Growth: +/− Appearance Mannitol Salt Agar Growth: +/− Appearance EMB Growth: +/− E. coli S. epidermidis A. faecalis S. aureus BSL-2 Unknown Number  Conclusions 1. Do your results support your hypotheses? 2. What two organisms are in your mixed culture? Could you identify them from the Gram stain? How did you identify them? 3. How did the results observed on the mannitol salt agar and EMB agar correlate to the Gram reaction of the bacteria? 4. Which medium is selective? Questions 1. What is the purpose of peptone in the media? 2. What is the purpose of agar in the media? Critical Thinking 1. What ingredient makes mannitol salt selective? 2. Fill in the blanks in this diagram to make a key to these bacteria: Escherichia coli Staphylococcus aureus Alcaligenes faecalis Staphylococcus epidermidis Circle or highlight the gram-positive bacteria in one color; use a different color to circle or highlight the gram-negative bacteria. Clinical Application Clinical samples are routinely inoculated onto differential and selective media. Determine whether the media listed below are selective or differential. a. Nutrient agar that contains vancomycin is selective or differential for b. EMB agar that contains sorbitol is used to select or differentiate E. coli O157. Explain: c. Nutrient agar with tellurite is selective/differential for.

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