They obtain energy from anaerobic respiration or fermentation. Aerotolerant anaerobes , like obligate anaerobes, cannot use oxygen for growth but they tolerate it fairly well. They obtain energy from fermentation. Facultative anaerobes are organisms that grow with or without oxygen, but generally better with oxygen. They obtain energy from aerobic respiration, anaerobic respiration, and fermentation.
Most bacteria are facultative anaerobes.
Psychrophiles are cold-loving bacteria. They are usually found in the Arctic and Antarctic regions and in streams fed by glaciers. Mesophiles are bacteria that grow best at moderate temperatures. Their optimum growth temperature is between 25C and 45C. Most bacteria are mesophilic and include common soil bacteria and bacteria that live in and on the body. Thermophiles are heat-loving bacteria.