Exercise 1: Hanging-Drop and Wet-Mount Preparations Essay

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W5_A2 Microbiology Lab Week 5 Review Sheet I Exercise 1: Hanging-drop and wet-mount preparations 1. How does true motility differ from Brownian movement? Brownian movement results from random motion of water molecules bombarding the bacteria and causing them to move. True motility and self- propulsion involves the 3 modes of motility. 2. What morphological structure is responsible for bacterial motility? Flagella 3. Why is a wet preparation discarded in disinfectant solution or biohazard container? Preparation has micro-organisms which can interact with the people or environment surrounding them 4. What is the value of a hanging-drop preparation? The hanging drop is a more complex technique, but it allows for longer-term observation and more reliable observation of motility. 5. What is the value of a wet-mount preparation? Wet mount preparation is valuable for demonstrating motility in microorganisms. Exercise 2: Simple stains 1. Define acidic and basic dyes. What is the purpose of each? Acidic dyes contain negative particles. Basic dyes contain positive particles used to stain bacteria because bacteria are negative. 2. What is the purpose of fixing a slide that is to be stained? Kills cells quickly by denaturing enzymes (this stops metabolic activity for more accurate staining). To adhere cells to slide better to prevent wash-off 3. Why are the specimens to be stained suspended in sterile saline or distilled water? We use sterile water because to avoid false result by microorganism having in the water and same reason for distilled also to avoid impurities like crystals of some metal ions and also to avoid other microorganisms. 4. How does a stained preparation compare with a hanging drop for studying the morphology and motility of bacteria? The hanging drop is the classical method for viewing unstained microorganisms; the

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