A student designs an experiment to produce an alcohol known as butanol. She mixes a species of Clostridium bacteria known to produce this alcohol as a by-product of its metabolism with a broth of water and glucose in excess, and incubates the mixture in constant darkness without any oxygen. For 5 days she notices an increase in bacterial biomass (amount of bacteria) AND in the amount of CO2 and butanol produced. After 1 1/2 weeks when she checks the culture, she observes that there has been a DECREASE in biomass and in the production of CO2 and butanol since her first check on the experiment. Plenty of glucose is still present in the culture and no mutations are found. For which of the following conclusions is the evidence the strongest? Choose one answer and explain why it is the best conclusion. You must also explain why the others wouldn't be correct for the problem.
a. Since ATP is formed during respiration. ATP has been formed in excess, poisoning the cells.
b. The bacterial cells have begun to utilize the CO2 and water to carry out photosynthesis.
c. After 1 1/2 weeks, the cells switched to aerobic respiration.
d. The alcohol produced has overpowered and inhibited the growth for the bacterial cells.
e. The bacterial cells have totally depleted their energy source and are no longer growing.