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Microbiolgy 203 Post Lab #5

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Microbiology 203 Post Lab#5- Ex. 1-5, 2-2, 3-4, 3-5

1. Assume you want to streak a trypticase soy agar plate for isolation using a nutrient broth culture of Staphylococcus epidermidis. A. Indicate how many times you would need to remove the cap from the S. epidermidis broth culture tube, and explain why. B. How many times would you need to flame your inoculating loop, and explain why.

Answers: A. The cap is removed one time when I obtain the original sample.

B. The loop will be flamed five times; one for each of the four streaks and once after the streak (Leboffe, 2012, p 41-42).

2. Indicate the goal in streaking a plate for isolation, and explain why it is important (Leboffe, 2012, p 41-42).

Answer: Streaking a plate for isolation is important because to test and identify the organism correctly it must be in individual colonies or a pure culture (Leboffe, 2012, p 41-42).

3. A. What two cellular characteristics are determined with the negative stain? B. Why is the bacterial smear not heat fixed before performing the negative stain?

Answers: A. The two cellular characteristics determined by negative stain is morphology (shape) and cellular arrangement in bacteria that cannot stand heat-fixing (Leboffe, 2012, p 165).

B. The bacterial smear is too fragile to withstand heat-fixing. Heat-fixing distorts shape and the cellular arrangement of the bacterial smear (Leboffe, 2012, p 165).

4. Differentiate between cellular morphology and colony morphology.

Answer: Cellular morphology is the difference of individual cells viewed under a microscope such as coccus, bacillus, vibrio, spirochete and colony morphology is viewed by the naked eye and the colonies are defined by their color, shape, margin, texture and appearance (Leboffe, 2012, p 59).

Leboffe, M., & Pierce, B. (2012). Microbiology: Laboratory theory and application (2nd...

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