Differential Media - Thioglycollate Medium

Differential Media:
Thioglycollate Medium
for the determination of the "oxygen relationship" designations
of chemoheterotrophic bacteria able to grow in this medium

This page was originally a handout for a couple of our microbiology
lab courses, and it is adapted from our Oxygen Relationship Page at
http://www.jlindquist.net/generalmicro/dfthiognf.html.

Some things to consider about the oxygen relationship test which uses utilizes Thioglycollate Medium (aka Thioglycollate Agar):
- The medium will support the growth of common, easily-grown chemoheterotrophic bacteria which are generally utilized in a basic microbiology course and also courses dealing with food and clinical microbiology. The pattern of growth of an inoculated organism will indicate three things: (1) whether or not an organism can respire using O₂, (2) whether or not an organism can ferment, and (3) whether or not the organism can simply tolerate atmospheric oxygen.
- Recall that aerobic respiration and fermentation are two of several general processes in which organisms can break down things and obtain energy – a process called catabolism. Aerobic respiration is a much more efficient process in generating ATP and subsequent call mass. Fermentation is indifferent to the presence of oxygen, but it will be the only reason an organism will grow anaerobically in this medium. Other catabolic processes which are associated with anaerobic growth – anaerobic respiration (using an oxygen substitute such as nitrate) and anoxygenic phototrophy (essentially anaerobic photosynthesis) – do not apply in the formulation and use of Thioglycollate Medium.
- The amino acids and glucose in the medium can be respired, and glucose is especially important in being a generally fermentable energy source in the medium. (Some exceptional organisms such as certain species of Clostridium can ferment amino acids.)
- Some other laboratory tests correlate with oxygen relationship designations as we will see below. This fact becomes handy when Thioglycollate Medium is not available or is deemed difficult to analyze.
The results we see in Thioglycollate Medium are shown below. The accompanying table gives related information.

Corresponding tube no. above	1	2	3	4
Oxygen relationship designation ––»	STRICT (OBLIGATE) AEROBE	FACULTATIVE ANAEROBE	AEROTOLERANT ANAEROBE	STRICT (OBLIGATE) ANAEROBE
AEROBIC RESPIRATION	+	+	–	–
FERMENTATION	–	+	+	+
Ability to grow aerobically (oxygen tolerance)	+	+	+	–
Ability to grow anaerobically	–	+	+	+
Catalase reaction	+	+	–	–
Reaction in Glucose O/F Medium (for those able to grow well in the medium)	O or –	F
Response to sodium azide in a growth medium	SENSITIVE	SENSITIVE (under aerobic conditions)	RESISTANT	RESISTANT

As shown in the table above, an organism's oxygen relationship designation can be determined by a combination of other methods if Thioglycollate Medium is not utilized – i.e., (1) testing for fermentation in Glucose Fermentation Broth, (2) performing the catalase test, and (3) testing if the organism can grow in the presence of oxygen.
Note that with Thioglycollate Medium, we are able to differentiate two distinct patterns of growth for those classified in the usual textbook (including Bergey's Manual) definitions as "facultative anaerobes":
- Those which are indifferent to oxygen and have a strictly fermentative type of metabolism grow evenly throughout the medium. We term such an organism an aerotolerant anaerobe and set that off as an additional category of oxygen relationship.
- Those left in the facultative anaerobe category show greater concentration of growth at the top of the medium where oxygen is present and aerobic respiration (and a positive catalase reaction) is then possible. Comparing the degree of growth under aerobic vs. anaerobic conditions can be a good demonstration of the relative efficiencies of aerobic respiration and fermentation when it comes to generation of cell mass.

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including Differential Media and
Identification of Bacteria
• Site Outline of related pages

Page was last modified on 10/8/11 at 11:00 PM, CDT.
John Lindquist: new homepage, complete site outline.
Department of Bacteriology, U.W.-Madison

Differential Media: Thioglycollate Medium for the determination of the "oxygen relationship" designations of chemoheterotrophic bacteria able to grow in this medium

Differential Media:
Thioglycollate Medium
for the determination of the "oxygen relationship" designations
of chemoheterotrophic bacteria able to grow in this medium