The Bacteroides and Firmicutes, the most abundant organisms colonizing the human colon (large intestine), are obligate anaerobes that rely exclusively on fermentation rather than respiration. In response to injury or infection, cells of the immune system generate reactive oxygen species and reactive nitrogen species whose breakdown products, especially nitrate, can serve as electron acceptors for respiration by less-abundant facultative anaerobes such as the Enterobacteriaceae. Explain why the Enterobacteriaceae population flourishes while the Bacteroides and Firmicate populations dwindle during inflammation.