biochemical reaction - prac. microbiology
TRANSCRIPT
Bacteria vary in their metabolic & enzymatic activities.
Used in identification of different genera & species of bacteria.
Biochemical reactions are done on bacteria grown in pure culture.
Biochemical Reactions
1. Sugar fermentation2. Oxidase test3. Catalase test4. Coagulase test5. API Test
1. Sugar fermentationSugar media are composed of: Peptone water + 1% test sugar + Andrade’s indicator + A small inverted tube (Durham’s
tube) .
Sugar fermentation test
uninoculated
fermented with A only
Not fermented fermented with A & G
Glucose Lactose maltose mannite Sucrose
Sugar fermentation can be indicated by change colour of the medium from yellow to red.
+ve - ve+ve +ve +ve
1. Sugar fermentation1. Sugar fermentation
Catalase TestCatalase Test
H2O2 Catalase enzyme H2 O + O2
Air bubbles
Principle:
Procedure:
1
3 H2O2
2
Results:
Positive test: rapid appearance of gas bubbles.
Catalase –veCatalase +ve
Catalase TestCatalase Test
Catalase TestCatalase Test
Coagulase TestCoagulase TestPrinciple:
FibrinogenPlasma
Coagulase enzyme FibrinVisible Clot
Procedure:2
3Place at 37oC, observe for formation of visible clot for up to 4 hrs.
1 ml rabbit plasma
1
Coagulase Test
Coagulase -ve
Coagulase +ve
Principle:
Tetramethyl p-phenylene diamine hydrochloride(oxidase reagent)
colourless
Cytochrome oxidase enzyme
Indophenol(Purple colour)
within 1-2 min
Oxidase TestOxidase Test
Oxidase Test
API (Analytical Profile Index)
Incubation Interpretation acc. to given charts
Bacterial Typing
Classification of a certain species of bacteria into Types.Importance: Epidemiological investigation (e.g. food
poisoning)
Examples of Typing methods: bacteriophage typing bio-typing serotyping plasmid analysis + others
Bacteriophage TypingBacterial strain on surface of media + drops of different phages
homogenous bacterial growth + areas of lysis (= susceptibility)
Questions
1- In sugar fermentation, Andrade's indicator is added to the sugar media to test for gas production:
( ) True ( ) False2- In the coagulase test, coagulation of plasma
occurs in positive cases: ( ) True ( ) False3- Biochemical reactions must be done on a pure
culture of the organism to be identified: ( ) True ( ) False
M C Q4-Catalase test is: a) negative if oxygen bubbles are released b) positive if a visible clot is formed c) done by adding a drop of H2O2
d) done to test for the presence of urease enzyme5- Oxidase test is: a) done using catalase reagent b) positive when a deep purple color is produced c) positive after a few hours d) negative when a yellow color is produced
Thank youThank you