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Biochemical Test - Coggle Diagram
Biochemical Test
Carbohydrate Fermentation Test
Indicator
:
Phenol Red
- It acts as a pH indicator to detect the carbohydrate fermentation
Result
: Positive - yellow color & Bubble formation. Positive - yellow color & No Bubble formation. Negative - Red color & Bubble formation.
Media
: Phenol Red Broth (Glucose, Lactose, Sucrose, Mannitol) pH : 7.4
Principle
: Glucose ⟶ Organic acids+CO₂•H₂. Carbohydrates ⟶ Enzymatic breakdown⟶ Acetic acid.
Triple Sugar Ion Agar Test
Indicator
: Phenol red
Phenol red
- acts as a pH indicator to detect Carbohydrate fermentation.
Sodium thiosulfate
- Detects H₂S.
Ferrous Ammonium Sulfate
- Indicate H₂S.
Media
: Triple Sugar Ion Agar Test pH : 7.4
Principle
: Sugar⟶
Fermentation
⟶Acid+Gas. Sodium thiosulfate ⟶
Thiosulfate reductase
⟶H₂S⟶FeS⟶Black precipitate
Result
:
A/A
- All sugars fermented.
K/A
- Only glucose fermented.
K/K
- No sugar fermented.
H₂S
- Black color.
Gas production
- Gaps, Cracks, Lift up
Urease Test
Indicator
: Phenol red
Phenol red
- acts as a pH indicator to detects color change.
Urea
- Detect urease enzyme
Media
: Christensen's Urea Agar Base pH : 6.8
Result
:
Postive
: Formation of Pale Pink color.
Negative
: Returns yellow color
Principle
: Urea (NH₂CONH₂) + H₂O ⟶
Urease
⟶ 2NH₃ (Ammonia) + CO₂
Hydrogen Sulfide Production Test
Media
: Sulfide Indole Motility Agar, Triple Sugar Ion Agar pH : 7.4
Indicator
:
Sodium thiosulfate
- Detects H₂S.
Ferrous Ammonium Sulfate
- Indicate H₂S.
Reaction
: Gas is colorless, it reacts with Fe ions from ferrous. H₂S⟶
Ferric ions
⟶ FeS⟶ Black precipitate
Result
:
Positive
: Blackening of media.
Negative
: No blackening of media
Principle
: Organic Sulfur Pathway : Cysteine⟶
Cysteine desulfurase
⟶ Pyruvic acid+Ammonia+H₂S. Inorganic Sulfur Pathway : Sodium thiosulfate ⟶ Thiosulfate reductase ⟶H₂S+FAS. Used to identify the motility organism - Christmas tree formation.
