Ex 21 SIM Medium Sulfur Indole Motility Objectives

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

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

1. Sulfur Reduction Cysteine desulfurase releases H 2 S from S -containing amino acids Thiosulfate reductase releases H 2 S by allowing S 2 O 32 - to be final electron acceptor in anaerobic respiration Ferrous iron salt in medium leads to visible black precipitate (Fe. S) if H 2 S is produced

SIM medium after 24 h incubation. Table 21 -1: Sulfur Reduction Results and Interpretation Result Interpretation Black in the medium Sulfur reduction (H 2 S production) No black in the medium Sulfur not reduced Symbol +

2. Indole Production l See IMVi. C 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- Symbol tation Growth radiating outward from Motile the stab line + No radiating growth Not motile

SIM Medium Results and Interpretation? Tube 1: Tube 2: