Question

1.Describe how Thioglycollate medium works regarding oxygen dependency. Make sure to explain the difference between aerobic, anaerobic, and facultative microbes and where in the media they will grow. also provide an example of each (bacterial strain.) what is the purpose of the colored band at the surface of the medium

Answer 1

Thioglycollate medium is mainly developed to test the aerotolerance of microorganisms. In other words, it is defined as the enriched and differential medium that estimates the oxygen requirements of microbes. The dye resazurine in the medium turns pink in the presence of the oxygen.

The medium is used to distinguish :

1. obligate aerobes - These microbes does not produce oxygen, thus are found on the top of the tube (at top oxygen concentration is maximum). (Eg-mycobacterium tuberculosis)

2. obligate anerobes - these are poisoned by oxygen, thus are found at the bottom of tube. (eg- clostridium botulinum)

3. Facultative anaerobes - these gather at top of the tube and can survive in absence or presence of oxygen. (Eg- Staphylococcus anaerobe)

4. Microaerophiles - these cannot produce oxygen, thus are found on top of the tube (Eg- helicobacter pylori)

5. Aerotolerant organisms- Do not require oxygen but are not poisened by oxygen. These are evenly spread throughout the tube.

The coloured band is the redox indicator that turn into pink in the presence of oxygen.