Obligate Anaerobes Which are Sensitive to O₂ Would Be Found

Question

Obligate anaerobes which are sensitive to O₂ would be found growing
A) throughout a tube of thioglycolate broth.
B) only at the very top of a tube of thioglycolate broth.
C) only at the bottom of a tube of thioglycolate broth.
D) approximately one-third of the way down the thioglycolate broth.

Accepted Answer

Obligate anaerobes cannot tolerate oxygen, so they will grow in areas of the tube where there is little to no oxygen present. In a thioglycolate broth tube, the bottom of the tube contains the most reduced environment, making it the ideal place for the growth of obligate anaerobes. Additionally, since these organisms are sensitive to oxygen, they would not grow higher up in the tube where there is more oxygen present. Therefore, the correct answer is C, only at the bottom of a tube of thioglycolate broth.