MCB 229 "Fundamentals of Microbiology"
Study Guide for Final Lab Quiz: Part 1 of 2

  1. What is the difference between fermentation and anaerobic respiration?

  2. Two days after inoculating Durham tubes, you notice the indicator dye has turned from a red color to a yellow color, and there is gas production. Has the organism used fermentation or anaerobic respiration to grow?

  3. The Durham tubes were placed back in the incubator to grow for two more days, at which time you notice the yellow tubes are now red. What process has occurred and why did this happen?

  4. The following table lists the results for inoculation of organisms in nitrate broth tubes. Indicate the nitrogenous compound remaining after growth has occurred:

    Red color after adding sol'n A & B
    Red color after adding zinc
    Nitrate, Nitrite, or Dinitrogen gas?





  5. What catalytic function does zinc perform in tests using nitrate broth tubes?

  6. Would you expect anaerobic respiration to occur in Durham tubes? Why/Why not?

  7. Define the following terms:

  8. Describe how "Gas Paks" function in the ability to create anaerobic conditions for the growth of anaerobic bacteria.

  9. What is added to pyrogallic acid to allow for growth of anaerobic bacteria?

  10. Why is agar added to sodium thioglycollate tubes?

  11. Using the table below, answer the following questions:
    A. Which of the organisms is able to ferment AND respire anaerobically?
    B. Which of the organisms is only able to grow by anaerobic respiration?
    C. Which organism is aerobic?

    Durham Acid+Gas
    Pyrogallic acid Growth
    Plate growth in Gas Pak




  12. Colony forming units were counted from four plates, each of which was inoculated with a swab from the hand of an individual receiving a handshake. Person one shook hands with person two, who shook hands with person three, who then shook hands with person four. Determine the percent transmission of bacteria from person to person using the following data:

    % Transmission




  13. The process used by an organism to repair damage done by ultraviolet light is known as ____________________________.

  14. What is the difference between an antiseptic and a disinfectant?

  15. What is the difference between an agent that is bactericidal and one that is bacteriostatic?

  16. Name four factors that influence the rate of death of microorganisms exposed to UV light:

  17. A Schaeffer-Fulton stain is designed to detect the presence of ____________________, and will stain the cells a __________ color.

  18. In what phase of growth are endospores formed?

  19. Two plates were inoculated with Bacillus cereus. One plate contained glucose (Plate #1) and one plate did not (Plate #2). Endospores were detected for B. cereus colonies grown on Plate #2, but not on Plate #1. What process has likely occurred that could account for these results?

  20. In an experiment examining the effects of endospores on the ability of organisms to survive high temperatures, the following results were obtained:

    CFU before heat treatment
    CFU after high heat treatment

    A. If organism A and C are actually the same organism but A was a "young" culture grown just before inoculation and C was an "old" culture, what might explain the results observed?

    B. What kind of organism do you think B is?

  21. Soil bacteria encompass a wide range of nutritional types. Which type below DO NOT normally exist in soil?

  22. Clearly describe the method of "plate count".

  23. Why would undercounting be a factor to keep in mind in the process of plate counting?

  24. What is the "pour plate" method used in the soil testing experiment?

  25. Suppose you have an organism whose optimal growth temperature is 20 degree Celsius and its growth is greatly inhibited by temperatures above 35 degree Celsius. Would the pour plate method be an ideal method for isolating and growing these bacteria? Why or why not?

  26. Suppose you obtained 1 gram worth of soil and you diluted it with 99 ml of water. You then take 1 ml worth of the dilution and put it into another 99ml of pure water. What is the final dilution? Show work.

  27. True or False. Bacteria numbers in soil are generally lesser in the rhizosphere than anywhere else.

  28. In the Enumeration of Microbes in Soil experiment, why did you plate out duplicates of agar plates for each soil dilutions?

  29. You are trying to identify an unknown. You have discovered its colony morphology, physical attributes, Gram stain, et.. You are now trying to determine whether it has motility or not. What two tests would you perform to determine this organism's motility?

  30. In testing for Antibiotics, why was cross-streak performed?

  31. What is "seeding" with reference to bacterial growth in pure culture?

  32. Suppose you have Penicillium and Streptomyces. For the first plate you streak Penicillium across the midline of the agar plate. For the second plate, you did the same but with Streptomyces. After a few days of incubation, you then cross-streak these plates with the following organism:
    A with sensitivity to antibiotics of Penicillium
    B with sensitivity to antibiotic of Streptomycetes.
    C with sensitivity to both antibiotics.
    D with sensitivity to neither antibiotics.
    Which organism would you expect growth on both plates?

  33. Why is it ideal to incubate Thermophiles in temperatures above room temperature?

  34. In the scavenger hunt experiment, after enrichment and T-streaking, you think you the organism you are scavenging for. What is your next step?

  35. Differentiate between disinfectants and antiseptics.

  36. UV is a practical and effective technique for killing microbes that interacts directly with __________.

  37. Define 2 of the following terms.

  38. Why is MacConkey Agar selective for coliforms?

  39. What is importance of sodium azide in SF medium?

  40. What required elements will each of the following media ingredients supply to microorganisms?

  41. What are selective media and differential media? Give an example of each.

  42. What is the purpose of the Schaeffer-Fulton Staining Method?

  43. Give two structural morphologies of fungi that are not present in bacteria.

  44. What is the gram stain of yeast and why?

  45. What are some of the morphological characteristics of the molds Aspergillus niger and Penicillium chrysogenum that can be seen using the microscope?
  46. Is Saccharomyces cerevisiae a bacterium or a yeast? How would you determine this in the lab if you did not know?
  47. Is Staphylococcus epidermis a bacterium or a yeast? How would you determine this in the lab if you did not know?
  48. For what purpose would you use Sabouraud plates? What is the selective agent in this medium?
  49. Microbes are grown on a variety of media. When is liquid media used? Solid media?
  50. What is agar?
  51. What does an autoclave do?
  52. Distinguish between general purpose, selective and differential media.
  53. What type of media is TSB, SF and MacConkey?
  54. What type of microbes does azide inhibit?
  55. What type of microbes does high salt inhibit?
  56. How would you know if microbes have produced acid as a by-product in solid media? In liquid media?

  57. What is the gram stain of Bacillus cereus, Escherichia coli, Pseudomonas aeuriginosa, Streptococcus faecalis, Staphylococcus aureus, and Salmonella typhimurium?
  58. Many microbes cannot digest lactose. Which of the microbes in the previous question is lactose positive?
  59. What is the definition of burst size?

  60. What is the target of Streptomycin?

  61. In the antibiotics lab, why are we using Penicillium and Streptomyces species in our first streak?

  62. What is the purpose of growing cells in the presence of penicillin and/or ampicillin?

  63. Describe lytic infection of a bacterium.

  64. What color are Lac Z- colonies on:
    MacConkey-Lactose medium
    MacConkey-Lactose medium with IPTG

  65. What color are Lac Y- colonies on:
    McConkey-Lactose medium
    McConkey-Lactose medium with IPTG

  66. (a) What are bacteriophages
    (b) What bacteriophage did you work with in this lab?

  67. Why can't we repeat penicillin enrichments till we get all lac-minus mutants?

  68. What is multiplicity of infection?

  69. A white colony detected in your mutant hunt was transferred to a MacConkey + IPTG plate and found to produce red colonies. Was the transferred colony LacZ- or LacY-? What process allows for the formation of red colonies from a colony that is lac-?

  70. Why would an infected culture mixed with chloroform result in a greater number of progeny viruses released by the infected cells when compared to a culture that was not mixed with chloroform?

  71. The following are results obtained from the mutant hunt lab. Briefly explain (discuss) what they mean ( HINT: what does the colony color suggest about the lactose?)
    Lac Z
    Lac Y
    MacConkey-lactose + IPTG
    Lac Z
    MacConkey-lactose + IPTG
    Lac Y

  72. Briefly describe the cross-streak method.

  73. Define a broad-spectrum antibiotic.

  74. What is "aseptic technique"? Why is this a better term than "sterile technique"?

  75. What is the importance of aseptic technique?

  76. Quadrant streaking (T-streaking) is a quick and economical method often used in dealing with microorganisms. What is the goal of this method? Briefly discuss the procedure or illustrate it.
  77. Why do you need to sterilize the inoculating loop each time you move from section to section?
  78. Would this procedure be any different if a swab was used instead of a loop?

  79. Why is it important to keep agar plates inverted during incubation?

  80. The gram stain is an important differential stain.
    (a) Bacteria which retain the crystal violet stain are ________.
    (b) Bacteria which do not retain the stain are __________.
    (c) Why is it important to use young cultures instead of old cultures when performing this method?
  81. You are given a gram negative organism. After staining you discover that the cells appear purple under oil immersion. Give 3 explanations that can account for your results.

  82. The best way to differentiate between the yeast Saccharomyces cerevisiae and the bacterium Staphylococcus aureus is by: _______________________

  83. When immersion oil is used, why is the resolution increased?

  84. Why has it become common practice to look for indicator organisms when detecting fecal contamination of water?

  85. What are the most frequently used indicator organisms and why?

  86. How is EMB media both selective and differential?

  87. For reliable statistics, one should count plates with what range of colonies on them?

  88. Describe the results one should expect from a positive completed water test.
  89. Based on the dilution series stated and the plate count provided, estimate the number of colony forming units per ml of the original sample in the sample flask described below.
    TUBE 1
    TUBE 2
    TUBE 3
    TUBE 4

    0.1mL of the sample flask was transferred to tube 1. 0.1mL of tube 1 was transferred to tube 2. 1mL of tube 2 was transferred to tube 3. 1mL of tube 3 was transferred to tube 4. Plates from the culture mixtures of tube 3 and tube 4 were plated. 61 CFU were found on the plate from tube 3 and 5 CFU were found on the plate from tube 4.

  90. Why do we make slants for each culture we are trying to isolate?

  91. How can we distinguish E.coli from other coliforms?

  92. Name 2 sources where you could possibly obtain a thermophile.

  93. Which species in your scavenger hunt has the characteristic of powdery or wrinkled appearances?

  94. I am a large, gram-negative, aerobic, nitrogen-fixing rod shaped bacteria. Which species do I belong to?

  95. I am a member of Archaea and stain gram-negatively. I do not form spores. I have a cell morphology of a rod, coccus, and a pleomorphic rod. What type of bacteria am I and what is another characteristic of cell morphology that I can be?

  96. What is a nodule?

  97. What are several tests you can perform to confirm that you have a pure culture of Bacillus fastidiosus?