SOME METABOLIC ACTIVITIES OF BACTERIA

Question 1

What are the broth cultures used for the some metabolic activities of bacteria experiment?

Answer 1

Escherichia coli
Pseudomonas aeruginosa (lvl 2)
Bacillus subtilis
Proteus mirabilis (lvl 2)

Question 2

Fermentation of Carbohydrates:
What type of tubes are included to trap any gas formed when the broth is inoculated and cultured?

Answer 2

Durham tube

Question 3

What type of colour indicator used for fermenting carbohydrates to indicate a change in pH, if acid is produced?

Answer 3

bromocresol purple

Question 4

T or F:
Organisms that do not ferment the carbohydrate may produce alkaline end products

Answer 4

True

Question 5

Production of Indole-
T or F:
Indole is a by-product of the metabolic breakdown of the amino acid tryptophan

Answer 5

TRUE

Question 6

What type of reagent is added to demonstrate the presence of indole in producing a brilliant red colour?

Answer 6

Kovac reagent

Question 7

T or F:
If tryptophan, and no indole, is present there will be no colour except the reagent itself.

Answer 7

TRUE

Question 8

Activity of Urease:
What type of products released when splitting the urea molecule?

Answer 8

Carbon dioxide and ammonia

Question 9

What type of indicator used for the activity of urease?

Answer 9

Phenol red

Question 10

What is the result detected of the degradation of urea with the release of ammonia

Answer 10

pH becomes alkaline and pH indicator colour becomes dark pink

Question 11

What is the characteristic of Proteus species?

Answer 11

Rapid production of urease

Question 12

Production of Hydrogen sulfide:
What is produced when amino acids containing sulfur are metabolized by microorganisms?

Answer 12

Hydrogen sulfide

Question 13

If the medium contains metallic ions (lead, bismuth or iron) and combines with it, what would be the result?

Answer 13

It will form a metal sulfide that blackens the medium

Question 14

What medium is convenient for testing hydrogen sulfide production?

Answer 14

SIM medium (contains iron for blackening)

Question 15

What do the colours represent when bromocresol purple was used in carbohydrate fermentation?
- Yellow
- Dark Blue
- Purple

Answer 15

• Acid
• Alkaline
• Neutral

Question 16

What are the results for each organism in carbohydrate fermentation?
- Escherichia coli
- Pseudomonas aeruginosa
- Bacillus subtilis
- Proteus mirabilis

Answer 16

• Acid, Acid, Neutral (all have gas formed)
• Neutral, Neutral, Neutral
• Acid, Neutral, Acid
• Acid (G), N(G), Neutral

Question 17

What are the 3 types of base broth used for this experiment?

Answer 17

Glucose, Lactose and Sucrose

Question 18

What are the results for the indole production? (the colour of surface ring and presence of production)

Answer 18

• E.coli - pink and +
• P. aeruginosa, B. subtilis, P. mirabilis : yellow and -

Question 19

What are the results for urease activity (when urea is broken down)

Answer 19

ALL except Proteus mirabilis showed pink after incubation and + urease activity

Question 20

What are the results for hydrogen sulfide production (blackening of the medium)

Answer 20

ALL except Proteus mirabilis had a black colour of SIM medium (+)

Question 21

What was the indicator used in the carbohydrate tubes?

What are the colours in acidic and basic conditions?

Answer 21

Bromocresol purple (yellow & purple)

Question 22

How was gas production detected in the carbohydrate tubes? What are the two types of gases that may be produced?

Answer 22

Durham tubes for trapping any formed gases (gas & no gas trapped)

Question 23

Explain the chemical mechanism for detecting indole in a bacterial culture?

Answer 23

by adding Kovac’s reagent that produces a red reagent layer

Question 24

Account for the development of alkalinity in cultures capable of using urea as a substrate

Answer 24

degradation of urea w/ release of ammonia can be detected when the pH becomes alkaline and dark pink (indicator)

Question 25

Blackening in media containing metallic ions indicates the production of what?

Answer 25

Production of Hydrogen Sulfide

Question 26

When testing for fermentation of carbohydrates, what colour would the tubed broth be for a positive test?

Answer 26

Yellow