Practical #2

Question 1

What is the purpose of the phenol red in the carbohydrate fermentation broth?

Answer 1

It is an acid indicator

If the acid is produced it will turn yellow

Question 2

What is the purpose of the Durham tube and the carbohydrate fermentation broth?

Answer 2

It is a gas indicator

If gas is produced it will leave a gas bubble in the Durham tube

Question 3

What are the three possible in products of fermentation?

Answer 3

Acids alcohol gasses

Question 4

What is the main product from the catalyst test causing the bubbling

Answer 4

Oxygen

Question 5

What bacterial genera are differentiated using the catalase test?

Answer 5

Enterococcus

Staphylococcus

Great for gram +

Question 6

Would an obligate anaerobe be positive for catalase? how do you know?

Answer 6

Not positive

they must live in an environment without O2

they lack catalase

they don’t need oxygen

Question 7

The oxidase test Is used to differentiate between which groups of bacteria?

Answer 7

Obligate Aerobes and facultative anaerobes

Question 8

Why should a metal loop not be used to transfer bacteria in the oxidase test?

Answer 8

The metal will transfer the electrons causing false positives therefore you need to use wooden sticks metal is a great conductor

Question 9

What in product reacts with nitrate a and nitrate b reagents?

Answer 9

Nitrite

Question 10

What is the function of zinc in the nitrate test?

Answer 10

Reduces NO3 to NO2

If nitrate is still there it turns red

Question 11

An unknown bacterium was inoculated into the sucrose fermentation tube was sucrose fermented

What are two of the three end products that you can detect with this test

What is the function of the Durham tube in the tube

Answer 11

1. Yes-yellow

no-red

Gas bubble-gas production

No gas bubble- no gas production

2. Acid, alcohol, gas
3. Gas detection

Catches gas

Question 12

Methyl red has been added to this tube. Is this a positive or negative test

Is this bacterium a butanediol fermenter or a mixed acid fermenter?

Answer 12

Red-positive

Yellow-negative

Mixed acid- positive for methyl red

Butanediol- positive for VP test

Question 13

This is the sim tube

Is this bacterium positive or negative for the sulfur test

is this bacterium positive or negative for the indole test

What is the substrate in this reaction that this bacterium is using for food?

Is this bacterium motile?

Answer 13

1. black-positive

clear-negative

2. red on top-positive

yellow or amber on top-negative

3. Tryptophan
4. Cloudy-positive

Not cloudy-negative-grows only in the line