Review Sheet: Brownian Movement

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Week 5 Review Sheet I Exercise 1: Hanging-drop and wet-mount preparations 1. How does true motility differ from Brownian movement? Brownian movement is caused by continuous, rapid oscillation of molecules in a fluid and thus this is irregular and non-directional. True movement will allow an organism to propel in a specific direction progressively. 2. What morphological structure is responsible for bacterial motility? Flagella are responsible for bacterial movement. 3. Why is a wet preparation discarded in disinfectant solution or biohazard container? They are discarded because the bacteria in the wet preparation are actually still alive. 4. What is the value of a hanging-drop preparation? The specimen does not lose…show more content…
5. List at least three types of bacteria whose names reflect their shapes and arrangements, and state the meaning of each name. Streptococcus (Coccus Shape) this is a spherical bacteria that causes Strep Throat. Lactobacillus (Bacillus Shape) this is a bacteria in the form of a rod that is usually in probiotics Spirillum Pulli (Spirillum Shape) this is a spiral bacteria in rat bite fever Exercise 3: Gram stain 1. What is the function of the iodine solution in the Gram stain? If it were omitted, how would staining results be affected? Iodine is used as a mordant, it combines with the dye in the Gram Stain. 2. What is the purpose of the alcohol solution in the Gram stain? This is used as the decolorizing agent 3. What counterstain is used? Why is it necessary? Could colors other than red be used? Safranin is the current counterstain being used. Other colors have been used in the past, such as a yellow color. 4. What is the advantage of the Gram stain over a simple stain such as methylene blue? The Gram stain uses special dyes and tells the difference between gram negative and gram positive…show more content…
Each of these result in individual colonies forming on the dish. 2. How do you decide which colonies should be picked from a plate culture of a mixed flora? This depends on whether the desired culture is pure or mixed. 3. Why is it necessary to make pure subcultures of organisms grown from clinical specimens? So that the organism can be identified and tested for antibiotic sensitivities. 4. What kinds of clinical specimens may yield a mixed flora in bacterial cultures? Oral, Skin, or GI specimens 5. When more than one colony type appears in pure culture, what are the most likely sources of extraneous contamination? Individual colonies can be picked up on the inoculating loop, or straight wire and inoculated in to the fresh agar or brother media References Cowan, M. K. (2012). MICROBIOLOGY: A SYSTEMS APPROACH, THIRD EDITION. In M. K. Cowan, Microbiology A SYSTEMS APPROACH THIRD EDITION (p. 90). New York: The McGraw-Hill Companies, Inc. Paul A. Granato, V. M. (2014). Microbiology: Applications to Patient Care Eleventh Edition. New York: McGraw-Hill

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