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DNase Test on Bacterial Colonies
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DNase Test on Bacterial Colonies

Created by
@ReceptiveNiobium

Questions and Answers

What is the purpose of adding methyl green dye to the DNase test agar plate?

  • To enhance the production of DNase
  • To inhibit bacterial growth
  • To visualize the clearing around bacterial growth (correct)
  • To facilitate the diffusion of DNA fragments

    • Staphylococcus aureus is a lipase-positive organism.

    False

    What is the primary function of lipases in bacterial identification?

    to break down fats

    The DNase test agar plate is incubated at a temperature of __________ for 24 hours.

    <p>35°C</p> Signup and view all the answers

    Which of the following is a application of the DNase test?

    <p>To identify Serratia species from Enterobacter species</p> Signup and view all the answers

    The DNase test agar plate is prepared with agar, tryptose, and sodium chloride only.

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

    Match the following components with their respective functions in the DNase test agar plate:

    <p>Deoxyribonucleic acid = Source of DNA for DNase to break down Methyl green = Visually detects DNA fragments Tryptose = Nutrient source for bacterial growth Agar = Solidifying agent</p> Signup and view all the answers

    What is the purpose of the control sector in the DNase test agar plate?

    <p>to serve as a reference for comparison with the test organisms</p> Signup and view all the answers

    What is the primary purpose of the lipase test?

    <p>To detect and enumerate lipolytic bacteria</p> Signup and view all the answers

    The lipase test is only used to detect lipolytic bacteria in dairy products.

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

    What is the incubation temperature and duration for the lipase test?

    <p>35°C for 24 to 28 hours</p> Signup and view all the answers

    The tributyrin agar plate is divided into _______ equal sectors.

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

    Match the following materials with their quantities in the media recipe:

    <p>beef extract = 3.0 g Peptone = 5.0 g Agar = 15.0 g Tributyrin oil = 10.0 ml Distilled water = 1.0 L</p> Signup and view all the answers

    The control sector on the plate is inoculated with one of the test organisms.

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

    What is the purpose of the control tube in the Gelatin Hydrolysis Test?

    <p>To differentiate between positive and temperature-induced results</p> Signup and view all the answers

    The Gelatin Hydrolysis Test is used to determine the ability of a microbe to produce urease.

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

    What is the name of the enzyme that catalyzes the depolymerization of DNA into small fragments?

    <p>Deoxyribonuclease (DNase)</p> Signup and view all the answers

    The medium recipe for Nutrient Gelatin includes ______________ g of gelatin.

    <p>120.0</p> Signup and view all the answers

    Which of the following organisms is gelatinase positive?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    Match the following tests with their respective purposes:

    <p>Gelatin Hydrolysis Test = Determine the ability of a microbe to produce gelatinases DNase Test = Determine the ability of a microbe to produce deoxyribonuclease (DNase)</p> Signup and view all the answers

    The DNA Hydrolysis Test is used to determine the ability of a microbe to produce caseinases.

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

    What is the purpose of the methyl green dye in the DNase test agar?

    <p>To form a complex with polymerized DNA, giving the agar a blue-green color</p> Signup and view all the answers

    Study Notes

    DNase Test

    • Bacterial colonies that secrete DNase (deoxyribonuclease) hydrolyze DNA in the medium, resulting in clearing around the growth.
    • DNase test agar plate contains DNA, peptides, and methyl green dye, which forms a complex that gives the agar a blue-green color.
    • This test is used to distinguish Serratia species from Enterobacter species, and Staphylococcus aureus from other Staphylococcus species.

    Lipid Hydrolysis Test

    • Lipid is a general term used to describe all types of fats.
    • Enzymes that hydrolyze fats are called lipases.
    • Bacteria can be differentiated based on their ability to produce and secrete lipases.
    • Tributyrin agar is prepared as an emulsion that makes the agar appear opaque.
    • When a plate is inoculated with a lipase-positive organism, clear zones will appear around the growth as evidence of lipolytic activity.
    • This test is used to detect and enumerate lipolytic bacteria, especially in high-fat dairy products.
    • Other lipid substrates, such as corn oil, olive oil, and soybean oil, are used to detect differential characteristics among Enterobacteriaceae, Clostridium, and Staphylococcus.

    Gelatin Liquefaction Test

    • Gelatin liquefaction is a positive result, but it's difficult to differentiate from gelatin that has melted as a result of temperature.
    • A control tube is incubated alongside the inoculated tubes to ensure accurate results.
    • This test is used to determine the ability of a microbe to produce gelatinases.
    • Staphylococcus aureus, which is gelatinase positive, can be differentiated from S. epidermidis using this test.

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    Description

    This quiz is about the DNase test used to identify bacteria that secrete DNase. It involves observing the clearing around bacterial growth on a DNase test agar plate.

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