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.
Mesophiles are organisms that grow best at moderate temperatures. Their optimum growth temperature is between 25C and 40C. Most bacteria are mesophilic. Thermophiles are heat-loving organisms. A colony is a visible mass of microorganisms growing on an agar surface and usually originating from a single organism or arrangement of organisms. Single colonies can be described using standard terms, as listed in Appendix A .