SERIES MICROBIOLOGY LAB PRACTICAL EXAM 2 COMPLETE QUESTIONS AND CORRECT ANSWERS | GRADED AND THE LATEST SERIES

Question: What is the purpose of the oxidase test? Ans: -The tests is used to identify bacteria containing the respiratory enzyme cytochrome c oxidase as an electron acceptor in the ETC. Question: How is the oxidase test performed? Ans: 1. Transfer bacterium to the paper 2. Add drops of complex A & B to bacterium 3. Observe for color change within 30 seconds Question: Why should you read the results of the oxidase test within 30 seconds? SERIES Ans: -The reagents of this test are unstable, therefore they may oxidize independently shortly after becoming moist. Therefore it is important to read within 30 seconds. Question: Catalase Test Ans: *Positive* -Visible Bubble production *Negative* -No Bubbles *Reagent Used:* -Hydrogen Peroxide Question: Why is the Catalase Test Used? Ans: -This test is used to identify organisms that produce the enzyme catalase, and its ability to break down hydrogen peroxide. Question: How is the catalase test performed? Ans: 1. Transfer a large amount of growth to slide 2. Place one to two drops of hydrogen peroxide on bacteria 3. Observe for bubbles Question: MacConkey Test SERIES Ans: *Poor Growth or No growth:* -Organism is inhibited by CV and/or bile, therefore is Gram-positive *Good Growth:* -Organism is not inhibited by CV and/or bile, therefore Gram-Negative *Pink to red growth with or without bile precipitate:* -Organism produces acid from lactose fermentation therefore is a probable coliform *Growth is "colorless" (not red or pink):* -Organism does not ferment lactose, therefore is a noncoliform Question: What does the bacteria look like on a MacConkey Media? Ans: *Negative Growth:* -Streak lines visible, but no colonies (Gram-positive) *Positive For Growth, but colorless:*