Cultivation of Anaerobes—Thioglycollate Broth, Atlas of Cultivation of Anaerobes—Thioglycollate Broth, A Photographic Atlas for the Microbiology Laboratory 4th edition 2011
Purpose
Fluid Thioglycollate Medium is a simple, inexpensive system for cultivating small numbers of anaerobic or microaerophilic bacteria. It is a liquid medium formulated to promote growth of a wide variety of fastidious anaerobic and microaerophilic microorganisms.
Principle
Fluid Thioglycollate Medium is prepared as a basic medium or with a variety of supplements, depending on the specific needs of organisms being cultivated. As such, it is appropriate for a broad variety of aerobic and anaerobic, fastidious and nonfastidious organisms. It is particularly well adapted for cultivation of strict anaerobes and microaerophiles.
Key components of the medium are yeast extract, pancreatic digest of casein, dextrose, sodium thioglycollate, L-cystine, and resazurin. Yeast extract and pancreatic digest of casein provide nutrients; sodium thioglycollate and Lcystine reduce oxygen to water; and resazurin (pink when oxidized, colorless when reduced) acts as an indicator. A small amount of agar is included to slow oxygen diffusion.
Oxygen is removed from the medium during autoclavingbut begins to diffuse back in as the tubes cool to room temperature. This produces a gradient of concentrations from fully aerobic at the top to anaerobic at the bottom. Thus, fresh media will appear clear to straw colored with a pink region at the top where the dye has become oxidized (Figure 3-42). Figure 3-43 demonstrates some basic bacterial growth patterns in the medium as influenced by the oxygen gradient.
3-42 AEROBIC ZONE IN THIOGLYCOLLATE MEDIUM
Note the pink region in the top (oxidized) portion of the broth.
The bottom (reduced) portion of the medium remains colorless.
3-43 GROWTH PATTERNS IN THIOGLYCOLLATE MEDIUM
Growth patterns of a variety of organisms are shown in these
Fluid Thioglycollate Broths. Pictured from left to right are:
aerotolerant anaerobe, facultative anaerobe, strict anaerobe,
strict aerobe, and microaerophile. Compare these tubes with
the uninoculated broth in Figure 3-42.
Suggested Reading
- Michael J. Leboffe & Burton E. Pierce. A Photographic Atlas for the Microbiology Laboratory 4th edition 2011
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