Fluid Thioglycollate Broth
Fluid Thioglycollate broth is a reducing medium. It contains sodium thioglycollate, which reacts with molecular oxygen keeping free oxygen levels low. The sodium thioglycollate in the broth creates a redox potential in the tube, with higher levels of oxygen at the top of the tube, and a complete absence of oxygen at the bottom of the tube. Fluid thioglycollate broth also typically contains a redox potential indicator such resazurin, which produces a pink color in an oxidized environment. As with the BHI media, organisms will only be able to grow where their oxygen requirements are met, and will localize to the area(s) of their oxygen requirements in the fluid thioglycollate broth
Tube 1: Obligate Anaerobe -- note the absence of growth in the top portion of the broth where oxygen is present.
Tube 2: Obligate Aerobe -- note the growth is only in the top portion of the tube where oxygen is present.
Tube 3: Aerotolerant -- note the uniform growth from top to bottom.
Tube 4: Facultative -- note the uneven distribution of growth from top to bottom (more growth at the top).
Tube 5: Obligate Aerobe -- note the growth is only in the top portion of the tube where oxygen is present.
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