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

Objectives ?

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

Day 1

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

1. Sulfur Reduction Cysteine desulfurase releases H2S from

S-containing amino acids

Thiosulfate reductase releases H2S by allowing S2O3

2- to be final electron acceptor in anaerobic respiration

Ferrous iron salt in medium leads to visible black precipitate (FeS) if H2S is produced

SIM medium after 24h incubation.

Table 21-1: Sulfur Reduction Results and InterpretationResult Interpretation Symbol

Black in the mediumSulfur reduction (H2S production)

+

No black in the medium Sulfur not reduced

2. Indole ProductionSee 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

Before addition of Kovac’s reagent

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

SIM Medium

Results and Interpretation?Tube 1:

Tube 2: