Microbiology Quiz: Citrate Test and DNA Hydrolysis
38 Questions
7 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the purpose of the citrate test?

  • To distinguish bacteria capable of growth in a citrate medium (correct)
  • To determine the ability of an organism to hydrolyze DNA
  • To differentiate organisms based on the production of deoxyribonuclease
  • To determine the growth of bacteria in a medium

    • What happens to the pH of the medium when bacteria grow in it?

  • It becomes alkaline (correct)
  • It changes randomly
  • It becomes acidic
  • It remains neutral

    • What is the function of the bromthymol blue indicator?

  • To determine the pH of the medium (correct)
  • To differentiate organisms based on the production of deoxyribonuclease
  • To determine the growth of bacteria in a medium
  • To determine the ability of an organism to hydrolyze DNA

    • What is the purpose of the DNA hydrolysis test?

    <p>To determine the ability of an organism to hydrolyze DNA</p> Signup and view all the answers

    What is the color of the DNA-methyl green complex?

    <p>Green</p> Signup and view all the answers

    What happens to the color of the medium if an organism can hydrolyze DNA?

    <p>It becomes colorless</p> Signup and view all the answers

    What is the primary purpose of the test described?

    <p>To determine the ability of an organism to produce and maintain stable acid end products</p> Signup and view all the answers

    What is the role of the MR indicator in the test?

    <p>To detect mixed acid fermentation</p> Signup and view all the answers

    What is the color of the MR indicator at pH 4.4?

    <p>Red</p> Signup and view all the answers

    What does a clear red result indicate?

    <p>A positive result</p> Signup and view all the answers

    What does the VP test detect?

    <p>The ability of an organism to convert acid products to acetoin and 2,3-butanediol</p> Signup and view all the answers

    What is the purpose of the VP test?

    <p>To determine the ability of an organism to convert acid products to acetoin and 2,3-butanediol</p> Signup and view all the answers

    What type of fermentation is detected by the MR indicator?

    <p>Mixed acid fermentation</p> Signup and view all the answers

    What is the result of a yellow MR indicator?

    <p>Negative result</p> Signup and view all the answers

    What is a characteristic of E. coli O157:H7?

    <p>It doesn't ferment sorbitol</p> Signup and view all the answers

    What is the primary reservoir of Edwardsiella tarda?

    <p>Reptiles and fresh water fish</p> Signup and view all the answers

    What is a common source of Salmonella transmission?

    <p>Poultry</p> Signup and view all the answers

    What is a characteristic of Shigella?

    <p>It is motile</p> Signup and view all the answers

    What is a common location for Shigella infection?

    <p>Day-care centers</p> Signup and view all the answers

    What is a characteristic of Citrobacter freundii?

    <p>It is motile</p> Signup and view all the answers

    What is a characteristic of Salmonella typhi?

    <p>It has a Vi antigen</p> Signup and view all the answers

    What is a way to differentiate Edwardsiella tarda from Salmonella?

    <p>Indole test</p> Signup and view all the answers

    What is the characteristic of Salmonella in the citrate test?

    <p>Colorless</p> Signup and view all the answers

    Which of the following bacteria is a Rapid Lactose Fermenter?

    <p>Klebsiella</p> Signup and view all the answers

    What is the characteristic of Enterobacter in the citrate test?

    <p>Produces pink color</p> Signup and view all the answers

    Which of the following bacteria is a Late Lactose Fermenter?

    <p>Hafnia</p> Signup and view all the answers

    What is the characteristic of Serratia in the citrate test?

    <p>Produces colorless medium at first, turning pink</p> Signup and view all the answers

    Which of the following bacteria is a Non-Lactose Fermenter?

    <p>Salmonella</p> Signup and view all the answers

    What is the characteristic of Proteus in the citrate test?

    <p>Produces colorless medium</p> Signup and view all the answers

    Which of the following bacteria is aerogenic?

    <p>Escherichia</p> Signup and view all the answers

    What is the primary function of the test that determines an organism's ability to hydrolyze tryptophan?

    <p>To hydrolyze tryptophan to pyruvate, ammonia, and indole</p> Signup and view all the answers

    What is the reaction between Kovac's reagent and indole?

    <p>Produces a red color</p> Signup and view all the answers

    What is the expected result of a positive test?

    <p>A pink to wine-colored ring forms</p> Signup and view all the answers

    What is the purpose of the Lysine Iron Agar (LIA) test?

    <p>To differentiate gram-negative bacilli</p> Signup and view all the answers

    What is the role of ferric ammonium citrate in Lysine Iron Agar?

    <p>It is the source of iron</p> Signup and view all the answers

    What happens to the butt of the Lysine Iron Agar medium when glucose is fermented?

    <p>It becomes acidic (yellow)</p> Signup and view all the answers

    What is the function of sodium thiosulfate in Lysine Iron Agar?

    <p>It detects the presence of hydrogen sulfide</p> Signup and view all the answers

    What is the composition of the medium in Lysine Iron Agar?

    <p>Lysine, peptones, glucose, ferric ammonium citrate, and sodium thiosulfate</p> Signup and view all the answers

    Study Notes

    Microbiology Laboratory Tests

    • Pyruvate can enter the organism's metabolic cycle for energy production
    • Bacteria capable of growth in citrate medium convert ammonium phosphate to ammonia and ammonium hydroxide, creating an alkaline pH
    • Bromthymol blue indicator turns from green to blue in the presence of alkaline pH

    DNA Hydrolysis (Dnase Test Agar)

    • Purpose: differentiate organisms based on deoxyribonuclease production
    • Principle: determines an organism's ability to hydrolyze DNA
    • Expected result: pink to wine-colored ring after adding Kovac's reagent

    Tryptophanase Test

    • Purpose: determines an organism's ability to hydrolyze tryptophan to form indole
    • Principle: tryptophanase-producing bacteria hydrolyze tryptophan to pyruvate, ammonia, and indole
    • Expected result: pink to wine-colored ring after adding Kovac's reagent

    Lysine Iron Agar (LIA)

    • Purpose: differentiates gram-negative bacilli based on decarboxylation or deamination of lysine and H2S formation
    • Principle: lysine iron agar contains lysine, peptones, glucose, ferric ammonium citrate, and sodium thiosulfate
    • Expected result: acid production (yellow) in the butt of the medium

    Methyl Red (MR) and Voges-Proskauer (VP) Tests

    • Purpose: determines the ability to produce and maintain stable acid end products from glucose fermentation
    • Principle: methyl red detects mixed acid fermentation, and VP detects the ability to convert acid products to acetoin and 2,3-butanediol
    • Expected result: clear red (positive), yellow (negative), or shades of orange (inconclusive)

    Bacterial Identification

    • Shigella: causes dysentery, found in crowded or substandard conditions
    • Edwardsiella tarda: opportunistic, found in reptiles and fresh water fish
    • Salmonella: causes typhoid fever, bacteremia, and enterocolitis, found in poultry
    • Citrobacter freundii: causes nosocomial infections
    • Klebsiella: causes pneumonia, found in humans and the environment
    • Enterobacter: causes opportunistic infections
    • Serratia: causes opportunistic infections
    • Proteus: causes urinary tract infections
    • Morganella: causes opportunistic infections
    • Providencia: causes opportunistic infections
    • Yersinia: causes plague and gastrointestinal infections

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    A quiz on microbiology tests, including citrate test and DNA hydrolysis, to identify bacterial growth and hydrolysis of DNA.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser