Micro Lab Quiz

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Micro Lab Quiz
2011-03-28 21:15:43
Microbiology Lab Terra

Microbiology Quiz 3/30
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  1. Selective media
    Used to inhibit grouwth of some organisms while encouraging the growth of others
  2. Differential media
    Contain indicators to expose differences between organisms
  3. Eosin Methylene Blue Agar (EMB)
    • Contains peptone, lactose, sucrose, eosin Y and methylene blue
    • Selective for Gram-negative organisms by inhibiting the growth of gram-positives
    • Differential for fermentation
  4. Mannitol Salt Agar (MSA)
    • Contains mannitol, 7.5% sodium chloride, and pH indicator phenol red
    • Selective by inhibiting gram-negatives
    • Differential by favoring the growth of Staphlycoccus and used to differentiate S. aureus from other Staph's
  5. Phenylethyl Alcohol Agar (PEA)
    • Contains phenylethyl alcohol that interferes with DNA synthesis in gram negatives
    • Selective by inhibiting gram-negatives
  6. MacConkey Agar (MAC)
    • Contains lactose, bile salts, neutral red, and crystal violet
    • Selective by inibiting gram-positives
    • Differential by lactose fermentation
  7. Blood Agar
    • Contains 5% sheep blood in a TSA base
    • Differential by ability to hemolyze RBC's
  8. Zone of Inhibition
    No immediate growth aroudn the disinfectant/antibiotic disk
  9. MIC
    Lowest antibiotic concentration that prevents visible bacterial growth
  10. Penicillin
    • Beta-lactam
    • Inhibits cell wall synthesis
  11. Erythromycin
    • Macrolide
    • Inhibitor of protein synthesis
  12. Ciprofloxacin
    Inhibits DNA replication
  13. Sulfamethoxazole and TMP
    Interuption of metabolic pathways
  14. MOA of UV
    Causes a thymine dimer and bacterial ribosome misreads DNA
  15. How does bacteria repair after UV exposure?
    It makes an enzyme called photolyase that fixes the mutation by using non-uv light
  16. What organism was used in the UV experiment?
    Serratia marcescens
  17. What was observed with:
    no lid?


    No growth/white colony

    No growth under shade

    full growth
  18. Psychrophiles
    Optimal 15° C can grow 0° to 20°
  19. Mesophiles
    Grow best at 20° to 40° C
  20. Thermophiles
    Grow above 45°C
  21. Hyperthermophiles
    Grow above 80°C
  22. What media was used to determine O2 requirements?
    Thioglycollate tube
  23. Obligate aerobes
    Need oxygen to grow
  24. Facultative anaerobes
    Will grow anywhere in medium but don't need oxygen
  25. Obligate anaerobes
    Can't grow in oxygen will be at bottom of medium
  26. Acidophiles
    grow well below pH 5.5
  27. Neutrophiles
    will grow between pH of 5.5 to 8.5
  28. Alkaliphiles
    grow well above pH of 8.5
  29. Phenol Red Durham Tube
    Used to determine the ability of some bacteria to ferment a particular carbohydrate has Durham tube in bottom to collect gas bubbles
  30. What would the results look like in a Durham Tube?
    Yellow/no bubbles=Acid/no gas


    Pink/no bubbles=Alkaline/no gas

  31. Triple Sugar Iron Tube
    • Contains lactose, sucrose, and glucose
    • pH indicator is Phenol red
    • Purpose of FeSO4 is to see if the organism generate H2S causes black precipitate
  32. What would results look like in a TSI tube?
    Yellow slant/yellow butt=glucose and lactose and/or sucrose were fermented

    Red slant/yellow butt=only glucose was fermented

    Red slant/red butt=none of the sugars were fermented

    Cracks or bubbles in yellow agar=gas was a byproduct of fermentation

    Black precipitate formed=H2S was produced
  33. E. coli
    What media will it grow on?
    What is the gram rxn?
    • EMB(metallic green) and MAC
    • Gram-negative
  34. S. aureus
    What media will it grow on?
    What is the gram rxn?
    • PEA, MSA(yellow), Blood Agar(beta hemolytic)
    • Gram-positive
  35. S. epidermidis
    What media will it grow on?
    What is the gram rxn?
    • PEA, MSA, Blood Agar(gamma hemolytic)
    • Gram-positive
  36. Bacillus subtilis
    What media will it grow on?
    What is the gram rxn?
    • PEA
    • Gram-Positive
  37. Shigella flexneri
    What media will it grow on?
    What is the gram rxn?
    • EMB
    • Gram-negative
  38. Enterobacter aerogenes
    What media will it grow on?
    What is the gram rxn?
    • EMB(lavendar)
    • Gram-negative