DNase Test on Bacterial Colonies

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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.

35°C Signup and view all the answers

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

To identify Serratia species from Enterobacter species Signup and view all the answers

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

False Signup and view all the answers

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

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 Signup and view all the answers

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

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

What is the primary purpose of the lipase test?

To detect and enumerate lipolytic bacteria Signup and view all the answers

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

False Signup and view all the answers

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

35°C for 24 to 28 hours Signup and view all the answers

The tributyrin agar plate is divided into _______ equal sectors.

three Signup and view all the answers

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

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

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

False Signup and view all the answers

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

To differentiate between positive and temperature-induced results Signup and view all the answers

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

False Signup and view all the answers

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

Deoxyribonuclease (DNase) Signup and view all the answers

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

120.0 Signup and view all the answers

Which of the following organisms is gelatinase positive?

Staphylococcus aureus Signup and view all the answers

Match the following tests with their respective purposes:

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

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

False Signup and view all the answers

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

To form a complex with polymerized DNA, giving the agar a blue-green color 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.