Which microorganism is an obligate aerobe?

Mycobacterium tuberculosis-the correct answer is d.mycobacterium tuberculosis is an important obligate aerobe to remember for usmle step 1. (other obligate aerobes include all other mycobacteria, bordetella pertussis, and francisella tularensis.). this organism can obtain energy only from respiration and must use oxygen as the terminal electron acceptor. primary infection occurs in the upper lobes of the lung. bacteroides fragilis(choice a) is an obligate anaerobic gram-negative bacillus that constitutes the primary organism found in the colon. it is the most common cause of anaerobic infections, including abdominal abscesses and peritonitis. clostridium perfringens(choice b), along with all the other clostridium species, is an obligate anaerobic, spore-forming, gram-positive bacillus. c. perfringens is an important cause of infection following trauma and surgery and can cause gas gangrene (which can be life-threatening if not treated). c. perfringens can also cause food poisoning. e. coli(choice c) and p. aeruginosa(choice e) are both facultative organisms, meaning that they can grow both in the presence or absence of oxygen. e. coli can ferment under anaerobic conditions or respire using oxygen as the terminal electron acceptor. p. aeruginosa cannot ferment. it respires only, using nitrate as the terminal acceptor under anaerobic conditions and oxygen as the terminal electron acceptor under aerobic conditions