Final answer:
Mitochondria that can switch between aerobic and anaerobic respiration, similar to facultative anaerobes, do well under stressful conditions, especially in cells that are adapted to low oxygen environments or require high amounts of energy.
Step-by-step explanation:
Under stressful conditions, mitochondria that are adapted to a high-stress environment can maintain performance and fitness better than those that are not. The most robust mitochondria under such conditions would likely be those found within cells that can operate under low oxygen conditions, such as facultative anaerobes, which are bacteria that can switch between aerobic respiration (using oxygen) and anaerobic respiration (without oxygen).
Mitochondria within muscle cells and other high-energy-demand cells tend to do well because they are more numerous and are adapted to the higher workloads these cells require. However, in particularly stressful conditions where oxygen is limited, cells would have to rely on less efficient energy production processes like glycolysis, which can operate without oxygen but produce less ATP (energy) compared to aerobic respiration.
Thus, mitochondria that are similar to those found in facultative anaerobes or in oxidative fibers with a high capacity for aerobic metabolism could fare better. These mitochondria are adept at producing energy efficiently under normal conditions and can switch to less efficient modes of ATP production when necessary.