Question

 

1. Why should you boil thioglycollate broth if it is not freshly made?
2. Which environment would a microaerophilic bacterium like the best?

Answer 1

Answer 1 :-

•Thioglycollate broth is the enrichment broth most frequently used in diagnostic bacteriology. This broth supports growth of anaerobes, aerobes, microaerophilic. It is a multipurpose, enriched, differential medium used primarily to determine the oxygen requirements of microorganisms. Sodium thioglycolate in the medium consumes oxygen and permits the growth of obligate anaerobes. fastidious microorganisms.

Composition of Thioglycollate broth

1.Pancreatic Digest of Casein: 15 gm.

2.Dextrose: 5.5 gm.

3.Yeast Extract: 5 gm.

4.Sodium Chloride: 2.5 gm.

5.thioglycollic acid and Sodium Thioglycollate: 0.5 gm.

6.L-Cystine: 0.5 gm.

7.Resazurin: 1 mg.

8.Agar 0.75 gm.

9.methylene blue,

•Actions of chemicals :- Dextrose, pancreatic digest of casein, yeast extract, L-cystine provide the growth factors necessary for bacterial multiplication.

1.L-cystine and sodium thioglycollate allows Clostridium and other strict anaerobes to grow in this medium even under aerobic conditions.

2.Sodium thioglycollate act as a reducing agent and neutralizes the toxic effects of mercurial preservatives and peroxides formed in the medium, thereby promoting anaerobiosis, and making the medium suitable to test materials containing heavy metals.

3.Resazurin: oxygen indicator; if the oxygen is present in broth the colour of Resazurin is pink, if the oxygen isabsent in broth the colour of Resazurin is clear .

4.At the bottom of tube xygen is absent and appear clear.

5.Sodium Thioglycollate and L-cystine convert the oxygen into water.

6.Incubation temperature is 36 degree and time 48 hrs.

•We should be reheated the broth by placing the bottle in a container of boiling water for 15 minutes (with bottle cap loosened) to drive off the dissolved oxygen.

Answer 2:-

Microaerophiles are microorganisms that are not killed outright by the presence of oxygen but are able to tolerate only sub-atmospheric levels of oxygen in their environment. ... Microaerophilic bacteria are examples of aerotolerant anaerobes. Microaerophilic need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube, but not the very top.

In our test tube Microaerophiles are growing in the border of aerobic and anaerobic zone.

• different growing zones in the test tube [containing broth]

1. Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.
2. Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.
3. Facultative anaerobes can grow with or without oxygen because they can metabolize energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration.
4. Microaerophilic need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube, but not the very top.at border of aerobic and anaerobic.
5. Aerotolerant organisms do not require oxygen as they metabolize energy anaerobically. Unlike obligate anaerobes, though, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.