SOME METABOLIC ACTIVITIES OF BACTERIA Flashcards
What are the broth cultures used for the some metabolic activities of bacteria experiment?
Escherichia coli
Pseudomonas aeruginosa (lvl 2)
Bacillus subtilis
Proteus mirabilis (lvl 2)
Fermentation of Carbohydrates:
What type of tubes are included to trap any gas formed when the broth is inoculated and cultured?
Durham tube
What type of colour indicator used for fermenting carbohydrates to indicate a change in pH, if acid is produced?
bromocresol purple
T or F:
Organisms that do not ferment the carbohydrate may produce alkaline end products
True
Production of Indole-
T or F:
Indole is a by-product of the metabolic breakdown of the amino acid tryptophan
TRUE
What type of reagent is added to demonstrate the presence of indole in producing a brilliant red colour?
Kovac reagent
T or F:
If tryptophan, and no indole, is present there will be no colour except the reagent itself.
TRUE
Activity of Urease:
What type of products released when splitting the urea molecule?
Carbon dioxide and ammonia
What type of indicator used for the activity of urease?
Phenol red
What is the result detected of the degradation of urea with the release of ammonia
pH becomes alkaline and pH indicator colour becomes dark pink
What is the characteristic of Proteus species?
Rapid production of urease
Production of Hydrogen sulfide:
What is produced when amino acids containing sulfur are metabolized by microorganisms?
Hydrogen sulfide
If the medium contains metallic ions (lead, bismuth or iron) and combines with it, what would be the result?
It will form a metal sulfide that blackens the medium
What medium is convenient for testing hydrogen sulfide production?
SIM medium (contains iron for blackening)
What do the colours represent when bromocresol purple was used in carbohydrate fermentation?
- Yellow
- Dark Blue
- Purple
- Acid
- Alkaline
- Neutral
What are the results for each organism in carbohydrate fermentation?
- Escherichia coli
- Pseudomonas aeruginosa
- Bacillus subtilis
- Proteus mirabilis
- Acid, Acid, Neutral (all have gas formed)
- Neutral, Neutral, Neutral
- Acid, Neutral, Acid
- Acid (G), N(G), Neutral
What are the 3 types of base broth used for this experiment?
Glucose, Lactose and Sucrose
What are the results for the indole production? (the colour of surface ring and presence of production)
- E.coli - pink and +
- P. aeruginosa, B. subtilis, P. mirabilis : yellow and -
What are the results for urease activity (when urea is broken down)
ALL except Proteus mirabilis showed pink after incubation and + urease activity
What are the results for hydrogen sulfide production (blackening of the medium)
ALL except Proteus mirabilis had a black colour of SIM medium (+)
What was the indicator used in the carbohydrate tubes?
What are the colours in acidic and basic conditions?
Bromocresol purple (yellow & purple)
How was gas production detected in the carbohydrate tubes? What are the two types of gases that may be produced?
Durham tubes for trapping any formed gases (gas & no gas trapped)
Explain the chemical mechanism for detecting indole in a bacterial culture?
by adding Kovac’s reagent that produces a red reagent layer
Account for the development of alkalinity in cultures capable of using urea as a substrate
degradation of urea w/ release of ammonia can be detected when the pH becomes alkaline and dark pink (indicator)
