Questions and Answers
What is the purpose of adding methyl green dye to the DNase test agar plate?
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.
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Which of the following is a application of the DNase test?
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The DNase test agar plate is prepared with agar, tryptose, and sodium chloride only.
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Match the following components with their respective functions in the DNase test agar plate:
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What is the purpose of the control sector in the DNase test agar plate?
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What is the primary purpose of the lipase test?
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The lipase test is only used to detect lipolytic bacteria in dairy products.
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What is the incubation temperature and duration for the lipase test?
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The tributyrin agar plate is divided into _______ equal sectors.
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Match the following materials with their quantities in the media recipe:
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The control sector on the plate is inoculated with one of the test organisms.
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What is the purpose of the control tube in the Gelatin Hydrolysis Test?
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The Gelatin Hydrolysis Test is used to determine the ability of a microbe to produce urease.
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What is the name of the enzyme that catalyzes the depolymerization of DNA into small fragments?
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The medium recipe for Nutrient Gelatin includes ______________ g of gelatin.
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Which of the following organisms is gelatinase positive?
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Match the following tests with their respective purposes:
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The DNA Hydrolysis Test is used to determine the ability of a microbe to produce caseinases.
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What is the purpose of the methyl green dye in the DNase test agar?
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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.