An anaerobic organism or anaerobe is any organism that doesn't require oxygen for growth and may even die in its presence. There are three types: obligate anaerobes, which can't use oxygen for growth and are even harmed by it; aerotolerant organisms, which can't use oxygen for growth, but tolerate the presence of it; and facultative anaerobes, which can grow without oxygen, but if present can utilize it. Metabolism Obligate anaerobes may use fermentation or anaerobic respiration.Aerotolerant or… (More on Anaerobe)