Page 104 - MNUmicrobiology practical 2025

General Microbiology & Immunology (PM 401) second level Semester 4 2024/2025

Christensen’s urea medium

• This medium used to test the ability of the organism to

produce urease enzyme which split urea in urea media to

form ammonia and CO2.

• The accumulation of the ammonia will produce alkaline PH

which turns the color of indicator (phenol red) into pink.

5- Media for aerobic & anaerobic organisms

Thioglycollate media
• Use: - Thioglycollate media are recommended for the cultivation of aerobic,

facultative, and anaerobic microorganisms

- Fluid Thioglycollate Medium is used for sterility testing of

biological specimens.

• The media is incubated at 30-35 C for 7 days

• Composition and role of each component:

• Small amount of agar in Thioglycollate Medium aids by

decreasing the diffusion of oxygen into the medium so assist

the growth of the anaerobes near the bottom and the aerobic

organism can grow near the top of the media.

• Sodium thioglycollate and cystine are a reducing agent which maintains low oxygen.

• Presence of indicator (resazorine) on the top of media to indicate the oxygen content.

General Microbiology & Immunology (PM 401) Practical note Page 93