An obligate aerobe is an aerobic organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to oxidize substances, like sugars or fats, in order to obtain energy. During respiration, they use oxygen as the terminal electron acceptor. They have the advantage of yielding more energy than obligate anaerobes, but face high levels of oxidative stress.
Examples of obligate aerobic bacteria: Nocardia (Gram-positive), and Mycobacterium tuberculosis (acid-fast). Pseudomonas aeruginosa (Gram-negative) is an obligate respirer (incapable of fermentation) but in the absence of oxygen, the bacteria respire using nitrate as a terminal electron acceptor. Some Bacillus species (Gram-positive) are capable of fermentation, although they grow slowly.
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