Biochemistry I Differential Tests
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Questions and Answers

Which organism is NOT listed under the Phenol Red Broth results?

  • Staphylococcus aureus (correct)
  • Enterococcus faecalis
  • Pseudomonas aeruginosa
  • Escherichia coli

    • Which test utilizes a slant medium and indicates hydrogen sulfide production?

  • Simmons Citrate Test
  • Utilization of Malonate Test
  • Carbohydrate Fermentation Test
  • Triple Sugar–Iron Agar Test (correct)

    • Which of the following organisms can ferment lactose?

  • Escherichia coli (correct)
  • Orphan
  • Proteus vulgaris
  • Pseudomonas aeruginosa

    • Which test specifically assesses an organism's ability to utilize malonate?

    <p>Malonate Broth Test (A)</p> Signup and view all the answers

    In the IMViC tests, which organism is associated with the Methyl Red Test?

    <p>Escherichia coli (C)</p> Signup and view all the answers

    Which of the following organisms is NOT identified in the Simmons Citrate Test?

    <p>Orphan (A)</p> Signup and view all the answers

    What is the primary function of the Triple Sugar Iron Agar Test?

    <p>Detect hydrogen sulfide and gas production (A)</p> Signup and view all the answers

    Which organism is most likely to produce hydrogen sulfide in the Triple Sugar–Iron Agar Test?

    <p>Salmonella spp (A)</p> Signup and view all the answers

    What color change indicates a positive result in the malonate test?

    <p>Blue (A)</p> Signup and view all the answers

    Which bacteria is used as the negative control in the malonate test?

    <p>E. coli (C)</p> Signup and view all the answers

    What is the principle of the malonate test?

    <p>The organism can utilize malonate as a carbon source. (C)</p> Signup and view all the answers

    What does a result of yellow in the phenol red indicating test signify?

    <p>Acidic pH (D)</p> Signup and view all the answers

    Which of the following indicates a neutral pH in the phenol red test?

    <p>Red (B)</p> Signup and view all the answers

    Which enzyme is involved in the process of fermentation noted in the phenol red basics?

    <p>Glycolytic enzymes (C)</p> Signup and view all the answers

    What is the effect of ammonia (NH3) release by bacteria on the pH of the media?

    <p>It raises the pH. (B)</p> Signup and view all the answers

    What is the role of bromthymol blue in the malonate test?

    <p>To monitor pH changes. (B)</p> Signup and view all the answers

    Flashcards

    Carbohydrate Fermentation

    A test used to identify bacteria based on their ability to ferment different carbohydrates, like glucose, lactose, and sucrose.

    Triple Sugar Iron Agar (TSI) Test

    A test used to determine the metabolic properties of bacteria, particularly those related to carbohydrate fermentation and sulfur production.

    IMViC Test

    A series of tests used to identify enteric bacteria, focusing on their metabolic reactions.

    Hydrogen Sulfide Test

    A test determining if a bacteria produces hydrogen sulfide gas.

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    Malonate Utilization Test

    A test measuring if a bacteria can use malonate as a source of energy.

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    Phenol Red Broth

    A broth used to look for how bacteria ferment.

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    Simmons Citrate

    A test to determine if bacteria can use citrate.

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    Methyl Red/Voges-Proskauer (MRVP) Test

    Tests for the presence of certain metabolic products related to glucose fermentation

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    Malonate Test

    A test to determine if an organism can use malonate as a sole carbon source.

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    Malonate Test Positive Result

    A positive result occurs if the organism utilizes malonate and the pH indicator changes from green to blue.

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    Malonate Test Negative Result

    A negative result occurs if the organism cannot utilize malonate and the pH remains green (below pH 6.9).

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    Phenol Red Fermentation Test

    A test determining if an organism can ferment a carbohydrate and produce acids or gases.

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    Phenol Red pH Indicator

    A chemical used to detect changes in pH. Pink is alkaline, red is neutral, yellow is acidic.

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    Fermentation (Microbiology)

    The process where an organism uses a carbohydrate (sugar) to produce acids or gases.

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    Malonate Broth

    A broth used in the Malonate test, containing malonate and a pH indicator.

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    E.coli in Malonate Test

    Serves as a negative control, indicating that it cannot utilize malonate as a carbon source.

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    Study Notes

    Differential Tests 1

    • Various tests used to determine bacterial characteristics.
    • Carbohydrate Fermentation tests include:
      • Triple Sugar-Iron Agar
      • IMVIC Test
      • Hydrogen Sulfide Test
      • Malonate Utilization

    General Enzymatic Action

    • Enzymes act on substrates (e.g., sucrose, composed of glucose and fructose).
    • Substrate binding to the enzyme forms an enzyme-substrate complex.
    • Enzyme strain on the substrate bond causes breakage.
    • Products are released.
    • Enzyme is free to bind more substrate.

    Biochemistry I

    • Various broth and agar tests used for bacterial identification.
    • Specific tests like Phenol Red (PR), Base Broth, Glucose Broth (GLU), Lactose Broth (LAC), and Sucrose Broth (SUC).
    • Methyl Red/Voges-Proskauer(MRVP) Broth
    • SIM (SIM Stab)
    • Triple Sugar Iron Agar (TSI)
    • Simmons Citrate (SC)
    • Malonate Broth (MAL)

    Malonate Test

    • Tests if an organism can use malonate as a sole carbon source.
    • Positive result: Media alkalinizes, pH indicator (bromthymol blue) changes from green to blue.
    • Negative control: E. coli
    • Positive control: Enterobacter aerogenes

    Phenol Red Basics

    • Phenol Red: pH indicator in media.
    • Pink at alkaline pH (>7.4)
    • Red at neutral pH (6.9-7.3)
    • Yellow at acidic pH (<6.8)
    • Fermentation of carbohydrate lowers pH (yellow).
    • Protein use raises pH (pink).
    • Durham tubes trap gas created during fermentation.
    • Alkaline reversion: Medium turns yellow initially, then red.

    Triple Sugar Iron Agar

    • Contains three fermentative sugars (lactose, sucrose, glucose).
    • pH changes via fermentation.
    • Different color combinations indicate fermentation results.
    • Blackening (H₂S) and gas production are observed in the agar. -Example of Escherichia coli, Salmonella, and Proteus vulgaris

    IMVIC Tests

    • Abbreviation for four biochemical tests (Indole, Methyl Red, Voges-Proskauer, Citrate).
    • Identifying and differentiating bacteria.
    • Useful with Gram-negative Enterobacteriaceae.

    Methyl Red/Voges-Proskauer Test

    • Used for Mixed Acid Fermentation and 2,3-Butanediol Fermentation.
    • Uses MRVP broth. -Use plastic pipette measure about 1 mL for each sample. -Label the tubes

    Mixed Acid Fermentation (Methyl Red)

    • Detects stable acid end products.
    • Indicator (methyl red) turns pink/red at acidic pH (<4.4).
    • Yellow: at neutral/alkaline (>7.2).
    • Orange: intermediate pH (4.4-6.2).
    • Positive result: pink/red color
    • Negative result: green/brown color

    2,3-Butanediol Fermentation (Voges-Proskauer (VP))

    • Detects acetoin (precursor to 2,3-butanediol and ethanol).
    • Barritt's reagents (a-naphthol and KOH) are added to detect acetoin.
    • Positive result: red color.
    • Negative result: no color change/copperish discoloration.

    Simmons Citrate Utilization Test

    • Tests if an organism uses sodium citrate as a carbon source.
    • Positive result: Medium turns deep blue.
    • Negative result: Medium remains green.
    • Indicator: Bromothymol blue.

    SIM Medium (Sulfur, Indole, Motility)

    • Tests for sulfur reduction, indole production, and motility.
    • Black precipitate: sulfur reduction.
    • Kovac's reagent: detects indole.
    • Motility: Growth throughout the agar.

    Carbohydrate Inoculations

    • Phenol Red is used to determine carbohydrate fermentation types.
    • Tests with different sugars (Glucose, Lactose, Sucrose).

    Carbohydrate Fermentation

    • Organisms classify based on their ability to utilize/ferment specific carbohydrates.
    • Classification based on acid/gas production (A/-, A/G).

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    Description

    Explore various differential tests utilized in Biochemistry I to identify bacterial characteristics. This quiz covers carbohydrate fermentation tests, enzymatic action, and other broth and agar tests essential for microbial identification. Test your knowledge on methods like Triple Sugar-Iron Agar and Malonate Utilization.

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