225 Lab Final (page 1)

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225 Lab Final (page 1)
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2012-07-26 23:40:46
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225 Lab Final (page 1)
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  1. Amylase Test:

    What is the medium used?

    What is the substrate?

    What is/are the product(s)?

    What is the reagent?
    Medium:  starch agar

    Substrate: starch

    Products: glucose, maltose, dextrins

    Reagent: Lugol's iodine
  2. Caseinase Test:

    What is the medium used?

    What is the substrate?

    What is/are the product(s)?

    What is the reagent?
    Medium: skim milk agar

    Substrate: casein

    Products: amino acids, peptides 

    Reagent: none used
  3. DNase Test: 

    What is the medium used?

    What is the substrate?

    What is/are the product(s)?

    What is the reagent?
    Medium: DNase agar 

    Substrate: ds DNA

    Products: nucleotides 

    Reagent: methyl green in agar (bound to DNA)
  4. Lipase Test:

    What is the medium used?

    What is the substrate?

    What is/are the product(s)?

    What is the reagent?
    Medium: spirit blue agar 

    Substrate: lipid (triglyceride)

    Products: glycerol, fatty acids 

    Reagent: spirit blue in agar (bound to triglycerides)
  5. What would be considered a positive result for each of the following tests?

    Amylase Test
    Caseinase Test
    DNase Test
    Lipase Test
    Amylase Test: + = colorless zone around organism after iodine is added

    Caseinase Test: + = clear zone around organism

    DNase Test: + = colorless zone around organism

    Lipast Test: + = blue/clear zone around organisms, blue ppt. in organisms
  6. Name one amylase positive bacteria.

    Name one caseinase positive bacteria.

    Name one DNase positive bacteria.
    B. subtilis produces both amylase and caseinase.

    S. aureus produces DNase.  
  7. What is the definition of selective media?

    What is the definition of differential media?  
    Selective media allows one type of bacteria to grow while inhibiting the growth of other types.  

    Differential media will change appearance based upon the type of bacteria growing in it.  

    Media is often constructed so that both selective and differential properties are present.  The addition of certain chemicals produces a selective media in which the growth of certain bacteria is selectively inhibited.  While the addition of other chemicals produces a differential media in which obvious differences in appearance occur among the different growing bacteria (p. 55).
  8. What are each of the following media selective for?  What are each of the following media differential for?

    Eosin Methylene Blue agar
    MacConkey's agar
    Mannitol Salt agar
    EMB agar and MacConkey's agar are both selective for gram negative bacteria (growth = gram negative) & differential for lactose fermentation

    MSA is selective for staph and differential for mannitol fermentation.
  9. EMB agar:

    Medium?
    Substrate?
    Selective Ingredient?
    pH indicator?
    • Medium: Eosin Methylene Blue (EMB) agar
    • Substrate: Lactose
    • Selective Ingredient: Eosin + Methylene Blue
    • pH indicator: none listed
  10. MacConkey's agar:

    Medium?
    Substrate?
    Selective Ingredient?
    pH indicator?
    • Medium: MacConkey's agar
    • Substrate: Lactose
    • Selective Ingredient: Crystal Violet + bile salts
    • pH indicator: Neutral red in agar
  11. MSA:

    Medium?
    Substrate?
    Selective Ingredient?
    pH indicator?
    • Medium: mannitol salt agar
    • Substrate: Mannitol
    • Selective Ingredient: 7.5% NaCl
    • pH indicator: Phenol red in agar
  12. What kind of bacteria can grow in EMB agar?

    How do you know if there is lactose fermentation in EMB agar?
    Only gram negative bacteria can grow in EMB agar.  

    In EMB media, lactose fermenters are indicated by the incorporation of a dye from the media into the bacteria, thereby, turning the bacteria to a distinctly dark purple or shiny metallic color.  The result is often shown by E. coli but may also appear with other bacteria such as Klebsiella pneumoniae.  The colonies may show a distinctive arrangement of color within the colony, known as fisheye.  The center of the colony is a dark purple and the rest of the outer portion of the colony area is a lighter pink color.  The fisheye colonies are often produced by Enterobacter aerogenes. (from pg. 62)
  13. What kind of bacteria can grow in MacConkey's agar?

    How do you know if there is lactose fermentation in MacConkey's agar?
    Only gram negative bacteria can grow in MacConkey's agar.

    Pink/red color to media/bacteria = lactose fermentation.  

    • + organisms are
    • E. coli
    • and
    • E. aerogenes
  14. What kind of bacteri can grow in Mannitol Salt Agar?

    How do you know if there is mannitol fermentation in Mannitol Salt Agar?
    Growth = salt tolerant (staphylococci)

    positive for mannitol fermentation = media is yellow

    negative for mannitol fermentation = media remains pink in color
  15. Indole Test:

    Media?
    Substrate?
    Products?
    Reagents?
    pH indicator?
    • Media: Tryptic Soy Broth (TSB)
    • Substrate: Tryptophan
    • Product: Indole
    • Reagent: Kovac's layered on top
    • pH indicator: none listed
  16. Methyl Red Test:

    Media?
    Substrate?
    Products?
    Reagents?
    pH indicator?
    • Media: MRVP broth
    • Substrate: Glucose
    • Products: Organic acids
    • Reagents: Methyl red
    • pH indicator: (Methyl red)
  17. Voges-Proskauer Test:

    Media?
    Substrate?
    Products?
    Reagents?
    pH indicator?
    • Media: MRVP broth
    • Substrate: Glucose
    • Products: Non-acids
    • Reagents: Barritts A and Barritts B
    • pH indicator: none listed
  18. Citrate Utilization Test

    Media?
    Substrate?
    Products?
    Reagents?
    pH indicator?
    • Media: Simmons' citrate agar
    • Substrate: citrate
    • Product(s): Na2CO3
    • Reagents: none listed
    • pH indicator: Bromthymol blue in agar
  19. For the Indole Test, what designates a positive result?

    Name one positive organism.
    The utilization of the substrate tryptophan by the bacteria is indicated by testing for the presence of indole by adding Kovac's reagent to the 2-day broth culture.  If indole is present, the layer of Kovac's reagent will almost immediately turn red in color (p. 66)

    E. coli produces a positive result like the one outlined above.
  20. For the Methyl Red test, what designates a positive result?

    Name one positive organism.
    Methyl red is one of a group of molecules that are pH indicators whose color is dependent on the pH.  It is yellow in color under basic conditions and red in color under acidic conditions.  The uninoculated media is basic in pH and when methyl red is added, a yellowish color is observed.  If the glucose (substrate) has been fermented to mixed acids, a decidedly red color will appear (positive result).  p. 67

    E. coli is an organism which will produce a positive result.  (red coloring throughout)
  21. For the Voges-Proskauer test, what designates a positive result?

    Name one positive organism.  
    Positive Result = the whole tube will eventually turn pink.  This reaction is very slow.  

    E. aerogenes produces the above result.  (whole tube eventually turns pink)
  22. For the Citrate Utilization test, what designates a positive result?

    Name one positive organism.  
    The bromthymol blue in the agar is green in color to start.  If the bacteria utilize citrate (the substrate), they will grow, produce alkaline end products, the pH will become basic, and the media/bromthymol blue will turn a royal blue color.  (p. 67)

    E. aerogenes is a bacteria which will produce the above positive result.  

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