Question

37. What does the enzyme catalase do (also see Chapter 6)? a. Detoxifies H.O, created in the oxidation of flavoprotein in the e' transport chain b. Detoxifies H,O, created by the action of superoxide dismutase c. Allows many aerobic, facultatively anaerobic, and microaerophil microbes to survive d. All of the above 38. What type of media is used in the catalase test (we will use the test tube version, not the slide) a. Agar plate b. Agar slant c. Agar deep d. Broth culture 39. Based on your previous experience, what will you use to inoculate the catalase test? a. Inoculating loop b. Inoculating needle c. Sterile serological pipette d. Sterile cotton swab 40. How will you know if catalase is present? a. Adding water will cause bubbles to form b. Adding H2O2 will cause O, bubbles to form c. Adding HOwill cause CO, bubbles to form d. None of the above 41. The next test you will use is Simmons Citrate Agar (Lab Exercise 5-7, check the box at the front of this section of labs). The Citrate Test is an example of which of the following? a. Decarboxylation enzyme test b. Hydrolytic exoenzyme test c. Nutrient utilization test d. Combination differential test 42. What type of media is used to culture the organism in a citrate test? a. Agar plate b. Agar slant c. Agar deep d. Broth culture 43. What enzyme brings citrate from the medium into the cell? A. Citrate percase B. Citrase C. Citrate dismutase D. Citrate dehydrogenase 44. How will you know if the microbe can utilize citrate? a. The media remains green b. The media turns blue c. Adding a reagent causes a blue color to form d. Adding a reagent causes a green color to form

Answer 1

Answers and explanation for 37 to 40 :

Catalase Test - Catalase is an enzyme produced by areobic microorganisms and some facultative anaerobes, to neutralise toxic by-products of oxygen metabolism e.g. H2O2

Catalase causes breakdown of hydrogen peroxide into water and oxygen as:

2H2O2   →  2H2O + O2 (bubbles)

37. d (All options are correct)

Since catalase-positive bacteria (staphylococci) has ability to respire using oxygen as a terminal electron acceptor, and helps microbe to survive by neutralising toxic by-products.

38. d. Broth culture media is used.

Since If using colonies from a agar or blood agar plate, we have to be very cautious not to scrape up any of the blood agar as blood cells are catalase positive and any contaminating agar (carryover of RBCs) will give a false positive.

Not a. because it's a agar

Not b. because it's a agar

Not c. because it's a agar

39. c.

Since using a metal loop or needle with H2O2 will degrade the metal and give a false positive.

Not a. because inoculation loop is metal

Not b. because inoculation needle is metal

Not c. because cotton swab will absorb H2O2

40. b. Adding H2O2 will cause oxygen bubbles to form, as seen in above equation.

Not a. because H2O is not added rather formed as by product.

Not c. because CO2 is not formed rather H2O2 is formed.