Return to Blog
Homepage
PCAT Biological Processes – Clostridium
- by
- Oct 24, 2017
- PCAT Question of the Day
A researcher places several colonies of Clostridium in a nutrient-rich broth but accidentally leaves the caps off the test tubes. Returning the next day, she notices that none of the tubes have shown bacterial growth. Which of the following is the most likely explanation for the lack of growth?
A) Oxygen from the air diffused into the broth and the lack of enzymes capable of breaking down the superoxide anion lead to death by oxygen toxicity.
B) Fungal spores in the air landed in the broth and the subsequent fungal growth consumed the available nutrients.
C) The ambient temperature of the air cooled the broth below the optimal growing temperature of 37ºC, causing the Clostridium to die off.
D) The failure to cap the test tubes was irrelevant and the Clostridium must have died due to some unknown factor.
Explanation
Clostridium is an obligate anaerobe. In the presence of atmospheric oxygen, the bacteria will die off. There are number of various factors that create oxygen toxicity but one of the major ones is the absence of enzymes necessary to deactivate toxic oxygen species. Thus (A) is the correct answer.
B: The question makes no mention of fungal growth and we have no reason to suspect that fungal spores in the air would be of a species capable of out-competing the bacteria for nutrients.
C: The ambient temperature in the room is unlikely to kill off bacteria. Cooler than optimal growing conditions may slow bacterial growth, but room temperature is unlikely to be fatal.
D: See explanation above for (A).
Related Post
Search the Blog
Free Consultation
Interested in our Online MCAT Course or one of our One-on-One MCAT Tutoring packages? Set up a free consultation with one of our experienced Academic Managers!
Schedule NowPopular Posts
-
-
-
-
-
MCAT Blog How to Review MCAT Full-Lengths
Free MCAT Practice Account
Need great MCAT practice?Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.
Learn More
Submit a Comment