Lab 5 Quiz Multiple Choice

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Questions and Answers

What indicates a positive result for casein activity in a skim milk plate?

Yellow coloration of the medium

No clear zone around bacterial growth

Clear zone around bacterial growth (correct)

Blue-black coloration after iodine addition

In the hydrolysis of urea, what is the product of urease activity?

Ammonia and carbon dioxide (correct)

Nitric acid and nitrogen gas

Uric acid and ammonia

Urea and hydrogen sulfide

What result would you expect if Bacillus subtilis were tested for amylase activity?

Color change to peach or yellow

No starch found near growth area (correct)

Clear zone around the bacterial growth

Color change to blue/black after iodine addition

What is the main purpose of the casein test in microbiology?

To evaluate protein breakdown ability Signup and view all the answers

What medium is used to test for urease activity in bacteria?

Urea slant Signup and view all the answers

What color indicates a positive urease activity result?

Pink Signup and view all the answers

Which of the following is a characteristic of Bacillus subtilis regarding starch?

It does not break down starch Signup and view all the answers

What outcome would indicate a negative result for urease activity on a urea slant?

Peach or yellow color Signup and view all the answers

What does amylase activity test for in bacteria?

Starch breakdown Signup and view all the answers

In a casein test, what does a negative result indicate?

No protein breakdown Signup and view all the answers

What indicates a positive result for gelatinase activity in gelatin deep media?

The media becomes liquid Signup and view all the answers

Which pH indicator is used in fermentation tubes to assess acid production?

Phenol red Signup and view all the answers

What color change indicates a negative result for starch hydrolysis?

Black Signup and view all the answers

Which of the following represents a condition for reading gelatin deep media?

Cool the tubes before observing Signup and view all the answers

What is the expected result in a Durham tube for a positive acid gas (AG) producing organism?

Yellow color with air bubbles Signup and view all the answers

What final product is formed when amylase breaks down starch?

Glucose Signup and view all the answers

In the fermentation tube experiment, what does a yellow broth indicate?

Acid production Signup and view all the answers

What is added to the starch agar plate after incubation to visualize the presence of starch?

Iodine Signup and view all the answers

Which procedure is appropriate for inoculating gelatin deep?

Use an inoculation needle to stab Signup and view all the answers

Which type of broth is specifically mentioned for identifying unknowns?

Lactose broth Signup and view all the answers

What is the primary purpose of using differential and selective media in bacterial identification?

To distinguish between bacterial species with similar appearances Signup and view all the answers

Which of the following biochemical tests evaluates a bacterium's ability to hydrolyze starch?

Starch hydrolysis Signup and view all the answers

What does a positive result in the indole test signify?

The ability to convert tryptophan into indole Signup and view all the answers

Which enzyme is associated with the hydrolysis of gelatin?

Gelatinase Signup and view all the answers

Which of the following bacteria might show a positive result for both glucose and lactose fermentation?

Escherichia coli Signup and view all the answers

What is indicated by a negative result in the catalase test?

The inability to decompose hydrogen peroxide into water and oxygen Signup and view all the answers

Why is knowledge of bacterial enzyme production significant in microbiology?

It provides insights into the bacterial genetic make-up Signup and view all the answers

Which test evaluates a bacterium's ability to utilize citrate as its sole carbon source?

Citrate utilization test Signup and view all the answers

What is the role of Durham tubes in carbohydrate fermentation tests?

To capture gas produced during fermentation Signup and view all the answers

Which of the following metabolic tests would indicate the ability of a bacterium to hydrolyze casein?

Casein hydrolysis test Signup and view all the answers

What color change indicates a positive test for citrate permease in Simmons Citrate media?

Blue Signup and view all the answers

What is the main purpose of bromothymol blue in Simmons Citrate media?

To detect the pH change Signup and view all the answers

Which of the following statements about catalase activity is true?

It is measured by observing bubble formation. Signup and view all the answers

What is the role of tryptophanase in the hydrolysis of tryptophan?

To hydrolyze tryptophan into indole, ammonia, and pyruvate Signup and view all the answers

In which type of environment is catalase produced by bacterial cells?

Oxygen-rich environments Signup and view all the answers

What does a yellow color indicate in the context of pH testing?

Acidic pH Signup and view all the answers

What observation is made to determine if a bacterium is capable of utilizing citrate?

Change from green to blue color Signup and view all the answers

What happens to tryptophan when tryptophanase is present?

It is broken down into indole, ammonia, and pyruvate. Signup and view all the answers

What inoculation method is commonly used for testing catalase activity?

Inoculating a TSA slant surface Signup and view all the answers

What is indicated by no change in the Simmons Citrate test?

The bacterium fails to take in citrate. Signup and view all the answers

Study Notes

Metabolic Activities of Bacteria

Bacterial species can be differentiated through metabolic testing
This is because Bacteria vary in their ability to produce enzymes
The enzymes a bacterial species can produce tells us something about its genetic make-up

Carbohydrate Fermentation

Some bacteria can ferment simple sugars or carbohydrates, producing acids and/or alcohol
Gas may also be produced
The different types of media used are: glucose broth, sucrose broth, and lactose broth
Phenol red is a pH indicator that is red at neutral pH
Yellow color indicates acid production
Red color indicates a negative result
An air bubble in the Durham tube indicates gas production

### Hydrolysis of Gelatin

The enzyme gelatinase breaks down gelatin (protein), producing peptides and amino acids
The media used is gelatin deep
A positive result for gelatinase activity is indicated by a liquid in the agar
A negative result is indicated by a solid agar
It is important to cool the tubes before reading results to ensure any liquid is not the result of melting

Hydrolysis of Starch

The enzyme amylase breaks down starch into dextrin, glucose, and maltose
The media used is starch agar plate
Iodine is used to detect the presence of starch by changing to a blue/black color
A positive result for amylase activity will show no starch present near the growth, resulting in no color change
A negative result for amylase activity shows starch present in the media, resulting in blue/black color change after iodine is added

Hydrolysis of Casein

Caseinase breaks down casein (milk protein) into amino acids
The media used is skim milk plate
A positive result for casein activity is indicated by a clear zone around bacterial growth
A negative result is indicated by no clear zone

Hydrolysis of Urea

Urease breaks down urea in to NH3 and CO2
The alkaline pH is detected in media
The media used for this test is urea slant
A positive result is indicated by a pink color
A negative result is indicated by no color change (peach or yellow color)
A yellow color indicates acidic pH and is not positive for urease

Citrate Utilization

Bacteria that can utilize citrate for energy grow on Simmons Citrate media
The media contains bromothymol blue, which is green at neutral pH and turns blue in alkaline pH
A positive result is indicated by blue color, which means an alkaline pH
A negative result is indicated by a lack of change

Catalase Activity

Catalase is an enzyme that cells produce when they live in an oxygen environment
Catalase breaks down H2O2 (hydrogen peroxide) into H2O and O2
The media used for this test is TSA slant
A positive result is indicated by bubbles, which is the free oxygen forming
A negative result is indicated by no change

Hydrolysis of Tryptophan (Indole test)

Tryptophanase breaks down tryptophan, an amino acid, into indole, NH3 (ammonia), and pyruvate
The media is used to detect the indole

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Description

Test your understanding of bacterial metabolic activities, including carbohydrate fermentation and gelatin hydrolysis. This quiz covers key concepts such as enzyme production and the interpretation of test results using various media types and indicators.