aerobe
A microorganism that requires free oxygen for growth. During the process of respiration, oxygen is the fi nal electron acceptor in the electron transport chain in these organisms. There are several d ifferent categories of aerobes. Obligate aerobes die in the absence of oxygen. Microaerophiles thrive in the presence of low amounts of oxygen, and facultative anaerobes normally use oxygen but can switch to an anaerobic metabolism when oxygen is depleted. Aerobes are more effi - cient at producing energy than organisms that do not use oxygen.