Imagine that aliens are attempting to grow humans in sterile chambers. Much to the aliens' disappointment, these humans are sickly, despite the fact that they have no bacteria in their gastrointestinal tracts. What could these experiments tell you about how bacteria populate the human gut?
A)Bacteria are present in human sperm and eggs, and appear in the human stomach as soon as it develops.
B)Bacteria are present in the amniotic fluid, and could enter the human stomach during development or shortly after birth.
C)Bacteria are present in the environment, and populate the human stomach throughout the course of an individual's life.
D)Bacteria are present in the amniotic fluid, and could enter the human stomach during development or shortly after birth; bacteria are present in the environment, and populate the human stomach throughout the course of an individual's life.
E)All of these choices are correct.

Question

Quizplus · Accepted Answer

The fact that the sterile humans are sickly despite having no bacteria in their gastrointestinal tracts suggests that bacteria may play a crucial role in maintaining human health. The only logical explanations for how bacteria could populate the human gut are that they are present in the amniotic fluid (and enter during development or shortly after birth) and that they are present in the environment throughout an individual's life. Therefore, the best choice is D, as it combines both explanations.

Imagine That Aliens Are Attempting to Grow Humans in Sterile