This document summarizes various biochemical tests used to identify bacteria, including:
- Fermentation tests using Durham tubes to detect gas and acid production from carbohydrates.
- The IMVIC series of tests (Indole, Methyl Red, Voges-Proskauer, Citrate) which identify metabolic pathways and substrate utilization through color changes.
- Other common tests like catalase, coagulase, urease, and oxidase which detect enzymatic activity through production of gas or color changes.
Students are assigned to prepare SIM, MRVP, and SCA media, inoculate bacterial samples, interpret test results using described reagents and expected color changes, and submit a write-
3. BIOCHEMICAL ACTIVITIES OF BACTERIA:
Biochemical properties could be used as tools
of identification demonstrate certain
metabolic activity of microbes
Example : Fermentation – durham tubes
Carbohydrates, amino acids, organic
acids
1. gases – Carbone dioxide, methane, hydrogen
2. Acid production – use of indicators to detect
Either acid or gas or both can be collected
4. IMVIC - INDOLE TEST
Principle : product of hydrolysis of an amino acid
tryptophan
Media – SIM (Sulfide Indole Motility)
Reagent - (Ehrlich’s) Para-dimethyl-
aminobenzaldehyde
Positive result :(+) pink or red color
Negative Result : (-) absence of pink or red color
5. IMVIC - METHYL RED TEST
Methyl red is a pH indicator
Principle : production of sufficient acidity from
glucose
Media- MR-VP broth
(+) red - acid
(-) yellow - alkaline
6. IMVIC - VOGUES PROSKAUER
• production of acetyl-methyl carbinol
from glucose
•media: MR-VP broth
•reagent: 40% KOH
•Positive (+) result = production of
an eosin like color
7. IMVIC - CITRATE UTILIZATION TEST
Principle: utilizes citrate as a source of Carbon
Media :Simmon Citrate (SCA)
(+) blue color
(--) green color
8. OTHER COMMON BIOCHEMICAL TESTS:
Coagulase test
Catalase test
Urease test
Hemolysis test
Greig’s Test
Oxidase Test
Hydrogen Sulfide Test
9. ASSIGNMENT:
Find the other biochemical Tests & tabulate
them based on:
Working principle
Reagents & Media
Positive & Negative Results
10. WHAT TO DO?
Place all your glassware in a plastic bag
Autoclave 15 psi, 121 C, 15 minutes
Wash , clean and dry
Wrap and sterilize in the oven, 150 C, 45
minutes
11. MEDIA PREPARATION
Prepare 200 ml each ( for the whole class)
SIM
MRVP
SCA
Dispense into 4 test tubes
1 tube SIM
2 tubes MRVP
1 tube SCA ( Slant )
12. Inoculate with bacteria ( get from me )
Incubate in incubator 48 hours
Add the reagents ( from previous slides )
Check results
Make a one page write – up
Submit