1. Ex. 21: SIM Medium (Sulfur, Indole, Motility)
Objectives ?

2. Work in a team of two students
Day 1
Materials needed per team of two students:
SIM tubes (3)
Materials needed per table:
Three pure slant cultures, one each of:
Proteus vulgaris
Escherichia coli
Klebsiella pneumoniae
Work in a team of two students

3. Materials needed per team of two students:
Day 2
Materials needed per team of two students:
The 3 incubated SIM tubes from the last session.
Materials needed per table:
Kovac’s reagent

4. 1. Sulfur Reduction
Cysteine desulfurase releases H2S from S-containing amino acids
Thiosulfate reductase releases H2S by allowing S2O32- to be final electron acceptor in anaerobic respiration
Ferrous iron salt in medium leads to visible black precipitate (FeS) if H2S is produced

5. Table 21-1: Sulfur Reduction Results and Interpretation
SIM medium after 24h incubation.
Table 21-1: Sulfur Reduction Results and Interpretation
Result
Interpretation
Symbol
Black in the medium
Sulfur reduction (H2S production) +
No black in the medium
Sulfur not reduced 

6. Table 21-2: Indole Production Results and Interpretation
See IMViC
Table 21-2: Indole Production Results and Interpretation
Result
Interpretation
Symbol
Red in the alcohol layer of Kovac’s reagent
Tryptophan is broken down into indole and pyruvate +
Reagent color is unchanged
Tryptophan is not broken down into indole and pyruvate 

7. Before addition of Kovac’s reagent

8. Table 21-3: Motility Results and Interpretation
3. Motility Test
Table 21-3: Motility Results and Interpretation
Result
Interpre-tation
Symbol
Growth radiating outward from the stab line
Motile +
No radiating growth
Not motile 

9. SIM Medium The End Results and Interpretation? Tube 1: Tube 2:
Tube 1:  (1) Positive for H2S, (2) Negative for Indole production, (3) Positive for motility
Tube 2:  (2) Negative for H2S, (2) Positive for Indole production, (3) Undetermined motility
The End